vim-patch:9.1.0147: Cannot keep a buffer focused in a window

Problem:  Cannot keep a buffer focused in a window
          (Amit Levy)
Solution: Add the 'winfixbuf' window-local option
          (Colin Kennedy)

fixes:  vim/vim#6445
closes: vim/vim#13903

https://github.com/vim/vim/commit/215703563757a4464907ead6fb9edaeb7f430bea

N/A patch:
vim-patch:58f1e5c0893a

27 files changed, 3414 insertions, 23 deletions

diff --git a/runtime/doc/message.txt b/runtime/doc/message.txt
index c3154fc372..16d88407d5 100644
--- a/runtime/doc/message.txt
+++ b/runtime/doc/message.txt
@@ -114,6 +114,13 @@ wiped out a buffer which contains a mark or is referenced in another way.
 You cannot have two buffers with exactly the same name.  This includes the
 path leading to the file.
 
+							*E1513* >
+  Cannot edit buffer. 'winfixbuf' is enabled
+
+If a window has 'winfixbuf' enabled, you cannot change that window's current
+buffer. You need to set 'nowinfixbuf' before continuing. You may use [!] to
+force the window to switch buffers, if your command supports it.
+
 							*E72*  >
   Close error on swap file
 
diff --git a/runtime/doc/news.txt b/runtime/doc/news.txt
index 3029414500..3ba7c5e681 100644
--- a/runtime/doc/news.txt
+++ b/runtime/doc/news.txt
@@ -160,6 +160,8 @@ The following new APIs and features were added.
   • 'breakindent' performance is significantly improved for wrapped lines.
   • Cursor movement, insertion with [count] and |screenpos()| are now faster.
 
+• |'winfixbuf'| keeps a window focused onto a specific buffer
+
 • |vim.iter()| provides a generic iterator interface for tables and Lua
   iterators |for-in|.
 
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index edd5149621..f35700218c 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -6271,6 +6271,8 @@ A jump table for the options with a short description can be found at |Q_op|.
 			"split" when both are present.
 	   uselast	If included, jump to the previously used window when
 			jumping to errors with |quickfix| commands.
+	If a window has 'winfixbuf' enabled, 'switchbuf' is currently not
+	applied to the split window.
 
 						*'synmaxcol'* *'smc'*
 'synmaxcol' 'smc'	number	(default 3000)
@@ -7170,6 +7172,15 @@ A jump table for the options with a short description can be found at |Q_op|.
 	Note: Do not confuse this with the height of the Vim window, use
 	'lines' for that.
 
+			*'winfixbuf'* *'wfb'* *'nowinfixbuf'* *'nowfb'*
+'winfixbuf' 'wfb'	boolean	(default off)
+			local to window
+	If enabled, the buffer and any window that displays it are paired.
+	For example, attempting to change the buffer with |:edit| will fail.
+	Other commands which change a window's buffer such as |:cnext| will
+	also skip any window with 'winfixbuf' enabled. However if a command
+	has an "!" option, a window can be forced to switch buffers.
+
 			*'winfixheight'* *'wfh'* *'nowinfixheight'* *'nowfh'*
 'winfixheight' 'wfh'	boolean	(default off)
 			local to window  |local-noglobal|
diff --git a/runtime/doc/quickref.txt b/runtime/doc/quickref.txt
index 572dc8a841..4ef4392f92 100644
--- a/runtime/doc/quickref.txt
+++ b/runtime/doc/quickref.txt
@@ -939,6 +939,7 @@ Short explanation of each option:		*option-list*
 'wildoptions'	  'wop'     specifies how command line completion is done
 'winaltkeys'	  'wak'     when the windows system handles ALT keys
 'window'	  'wi'	    nr of lines to scroll for CTRL-F and CTRL-B
+'winfixbuf'	  'wfb'     keep window focused on a single buffer
 'winfixheight'	  'wfh'     keep window height when opening/closing windows
 'winfixwidth'	  'wfw'     keep window width when opening/closing windows
 'winheight'	  'wh'	    minimum number of lines for the current window
diff --git a/runtime/doc/tagsrch.txt b/runtime/doc/tagsrch.txt
index 2b5b253a09..ac2bf9337b 100644
--- a/runtime/doc/tagsrch.txt
+++ b/runtime/doc/tagsrch.txt
@@ -402,17 +402,22 @@ If the tag is in the current file this will always work.  Otherwise the
 performed actions depend on whether the current file was changed, whether a !
 is added to the command and on the 'autowrite' option:
 
-  tag in       file	   autowrite			~
-current file  changed	!   option	  action	~
- ---------------------------------------------------------------------------
-    yes		 x	x     x	  goto tag
-    no		 no	x     x	  read other file, goto tag
-    no		yes    yes    x   abandon current file, read other file, goto
-				  tag
-    no		yes	no    on  write current file, read other file, goto
-				  tag
-    no		yes	no   off  fail
- ---------------------------------------------------------------------------
+  tag in       file	                autowrite			~
+current file  changed	!   winfixbuf   option	      action	~
+ -----------------------------------------------------------------------------
+    yes		x	x      no         x         goto tag
+    no		no	x      no         x         read other file, goto tag
+    no		yes	yes    no         x         abandon current file,
+						    read other file, goto tag
+    no		yes	no     no         on        write current file,
+						    read other file, goto tag
+    no		yes	no     no         off       fail
+    yes		x	yes    x          x         goto tag
+    no		no	no     yes        x         fail
+    no		yes	no     yes        x         fail
+    no		yes	no     yes        on        fail
+    no		yes	no     yes        off       fail
+ -----------------------------------------------------------------------------
 
 - If the tag is in the current file, the command will always work.
 - If the tag is in another file and the current file was not changed, the
@@ -428,6 +433,8 @@ current file  changed	!   option	  action	~
   the changes, use the ":w" command and then use ":tag" without an argument.
   This works because the tag is put on the stack anyway.  If you want to lose
   the changes you can use the ":tag!" command.
+- If the tag is in another file and the window includes 'winfixbuf', the
+  command will fail. If the tag is in the same file then it may succeed.
 
 							*tag-security*
 Note that Vim forbids some commands, for security reasons.  This works like
diff --git a/runtime/lua/vim/_meta/options.lua b/runtime/lua/vim/_meta/options.lua
index 757720d8fb..e9ac2fe08f 100644
--- a/runtime/lua/vim/_meta/options.lua
+++ b/runtime/lua/vim/_meta/options.lua
@@ -6746,6 +6746,8 @@ vim.bo.swf = vim.bo.swapfile
 --- 		"split" when both are present.
 ---    uselast	If included, jump to the previously used window when
 --- 		jumping to errors with `quickfix` commands.
+--- If a window has 'winfixbuf' enabled, 'switchbuf' is currently not
+--- applied to the split window.
 ---
 --- @type string
 vim.o.switchbuf = "uselast"
@@ -7874,6 +7876,18 @@ vim.o.wi = vim.o.window
 vim.go.window = vim.o.window
 vim.go.wi = vim.go.window
 
+--- If enabled, the buffer and any window that displays it are paired.
+--- For example, attempting to change the buffer with `:edit` will fail.
+--- Other commands which change a window's buffer such as `:cnext` will
+--- also skip any window with 'winfixbuf' enabled. However if a command
+--- has an "!" option, a window can be forced to switch buffers.
+---
+--- @type boolean
+vim.o.winfixbuf = false
+vim.o.wfb = vim.o.winfixbuf
+vim.wo.winfixbuf = vim.o.winfixbuf
+vim.wo.wfb = vim.wo.winfixbuf
+
 --- Keep the window height when windows are opened or closed and
 --- 'equalalways' is set.  Also for `CTRL-W_=`.  Set by default for the
 --- `preview-window` and `quickfix-window`.
diff --git a/runtime/optwin.vim b/runtime/optwin.vim
index fc60f70335..5b5b33e4ad 100644
--- a/runtime/optwin.vim
+++ b/runtime/optwin.vim
@@ -444,6 +444,7 @@ if has("statusline")
   call <SID>AddOption("statusline", gettext("alternate format to be used for a status line"))
   call <SID>OptionG("stl", &stl)
 endif
+call append("$", "\t" .. s:local_to_window)
 call <SID>AddOption("equalalways", gettext("make all windows the same size when adding/removing windows"))
 call <SID>BinOptionG("ea", &ea)
 call <SID>AddOption("eadirection", gettext("in which direction 'equalalways' works: \"ver\", \"hor\" or \"both\""))
@@ -452,6 +453,8 @@ call <SID>AddOption("winheight", gettext("minimal number of lines used for the c
 call append("$", " \tset wh=" . &wh)
 call <SID>AddOption("winminheight", gettext("minimal number of lines used for any window"))
 call append("$", " \tset wmh=" . &wmh)
+call <SID>AddOption("winfixbuf", gettext("keep window focused on a single buffer"))
+call <SID>OptionG("wfb", &wfb)
 call <SID>AddOption("winfixheight", gettext("keep the height of the window"))
 call append("$", "\t" .. s:local_to_window)
 call <SID>BinOptionL("wfh")
diff --git a/src/nvim/api/vim.c b/src/nvim/api/vim.c
index 84a2f24dbc..24ad7d5fbc 100644
--- a/src/nvim/api/vim.c
+++ b/src/nvim/api/vim.c
@@ -876,6 +876,11 @@ void nvim_set_current_buf(Buffer buffer, Error *err)
     return;
   }
 
+  if (curwin->w_p_wfb) {
+    api_set_error(err, kErrorTypeException, "%s", e_winfixbuf_cannot_go_to_buffer);
+    return;
+  }
+
   try_start();
   int result = do_buffer(DOBUF_GOTO, DOBUF_FIRST, FORWARD, buf->b_fnum, 0);
   if (!try_end(err) && result == FAIL) {
diff --git a/src/nvim/api/window.c b/src/nvim/api/window.c
index ed51eedf1b..1a80e9ea16 100644
--- a/src/nvim/api/window.c
+++ b/src/nvim/api/window.c
@@ -61,6 +61,12 @@ void nvim_win_set_buf(Window window, Buffer buffer, Error *err)
   if (!win || !buf) {
     return;
   }
+
+  if (win->w_p_wfb) {
+    api_set_error(err, kErrorTypeException, "%s", e_winfixbuf_cannot_go_to_buffer);
+    return;
+  }
+
   if (win == cmdwin_win || win == cmdwin_old_curwin || buf == cmdwin_buf) {
     api_set_error(err, kErrorTypeException, "%s", e_cmdwin);
     return;
diff --git a/src/nvim/arglist.c b/src/nvim/arglist.c
index a02c22deae..4d493c9d03 100644
--- a/src/nvim/arglist.c
+++ b/src/nvim/arglist.c
@@ -623,6 +623,8 @@ void ex_argument(exarg_T *eap)
 /// Edit file "argn" of the argument lists.
 void do_argfile(exarg_T *eap, int argn)
 {
+  bool is_split_cmd = *eap->cmd == 's';
+
   int old_arg_idx = curwin->w_arg_idx;
 
   if (argn < 0 || argn >= ARGCOUNT) {
@@ -637,10 +639,16 @@ void do_argfile(exarg_T *eap, int argn)
     return;
   }
 
+  if (!is_split_cmd
+      && (&ARGLIST[argn])->ae_fnum != curbuf->b_fnum
+      && !check_can_set_curbuf_forceit(eap->forceit)) {
+    return;
+  }
+
   setpcmark();
 
   // split window or create new tab page first
-  if (*eap->cmd == 's' || cmdmod.cmod_tab != 0) {
+  if (is_split_cmd || cmdmod.cmod_tab != 0) {
     if (win_split(0, 0) == FAIL) {
       return;
     }
diff --git a/src/nvim/buffer.c b/src/nvim/buffer.c
index 7154be36be..e141706edd 100644
--- a/src/nvim/buffer.c
+++ b/src/nvim/buffer.c
@@ -1305,6 +1305,12 @@ int do_buffer(int action, int start, int dir, int count, int forceit)
     }
     return FAIL;
   }
+
+  if (action == DOBUF_GOTO && buf != curbuf && !check_can_set_curbuf_forceit(forceit)) {
+    // disallow navigating to another buffer when 'winfixbuf' is applied
+    return FAIL;
+  }
+
   if ((action == DOBUF_GOTO || action == DOBUF_SPLIT) && (buf->b_flags & BF_DUMMY)) {
     // disallow navigating to the dummy buffer
     semsg(_(e_nobufnr), count);
diff --git a/src/nvim/buffer_defs.h b/src/nvim/buffer_defs.h
index 1e5086309c..7f7300706c 100644
--- a/src/nvim/buffer_defs.h
+++ b/src/nvim/buffer_defs.h
@@ -139,6 +139,8 @@ typedef struct {
 #define w_ve_flags w_onebuf_opt.wo_ve_flags  // flags for 'virtualedit'
   OptInt wo_nuw;
 #define w_p_nuw w_onebuf_opt.wo_nuw    // 'numberwidth'
+  int wo_wfb;
+#define w_p_wfb w_onebuf_opt.wo_wfb    // 'winfixbuf'
   int wo_wfh;
 #define w_p_wfh w_onebuf_opt.wo_wfh    // 'winfixheight'
   int wo_wfw;
diff --git a/src/nvim/ex_cmds.c b/src/nvim/ex_cmds.c
index 74ad8e95a2..14bd2b87e3 100644
--- a/src/nvim/ex_cmds.c
+++ b/src/nvim/ex_cmds.c
@@ -2008,6 +2008,10 @@ static int check_readonly(int *forceit, buf_T *buf)
 ///           GETFILE_OPEN_OTHER for successfully opening another file.
 int getfile(int fnum, char *ffname_arg, char *sfname_arg, bool setpm, linenr_T lnum, bool forceit)
 {
+  if (!check_can_set_curbuf_forceit(forceit)) {
+    return GETFILE_ERROR;
+  }
+
   char *ffname = ffname_arg;
   char *sfname = sfname_arg;
   bool other;
diff --git a/src/nvim/ex_cmds.lua b/src/nvim/ex_cmds.lua
index 1318eda5eb..e2196f99ec 100644
--- a/src/nvim/ex_cmds.lua
+++ b/src/nvim/ex_cmds.lua
@@ -812,7 +812,7 @@ module.cmds = {
   },
   {
     command = 'drop',
-    flags = bit.bor(FILES, CMDARG, NEEDARG, ARGOPT, TRLBAR),
+    flags = bit.bor(BANG, FILES, CMDARG, NEEDARG, ARGOPT, TRLBAR),
     addr_type = 'ADDR_NONE',
     func = 'ex_drop',
   },
diff --git a/src/nvim/ex_cmds2.c b/src/nvim/ex_cmds2.c
index 8016e37ca7..3120868350 100644
--- a/src/nvim/ex_cmds2.c
+++ b/src/nvim/ex_cmds2.c
@@ -444,6 +444,27 @@ int buf_write_all(buf_T *buf, bool forceit)
 /// ":argdo", ":windo", ":bufdo", ":tabdo", ":cdo", ":ldo", ":cfdo" and ":lfdo"
 void ex_listdo(exarg_T *eap)
 {
+  if (curwin->w_p_wfb) {
+    if ((eap->cmdidx == CMD_ldo || eap->cmdidx == CMD_lfdo) && !eap->forceit) {
+      // Disallow :ldo if 'winfixbuf' is applied
+      semsg("%s", e_winfixbuf_cannot_go_to_buffer);
+      return;
+    }
+
+    if (win_valid(prevwin)) {
+      // Change the current window to another because 'winfixbuf' is enabled
+      curwin = prevwin;
+    } else {
+      // Split the window, which will be 'nowinfixbuf', and set curwin to that
+      exarg_T new_eap = {
+        .cmdidx = CMD_split,
+        .cmd = "split",
+        .arg = "",
+      };
+      ex_splitview(&new_eap);
+    }
+  }
+
   char *save_ei = NULL;
 
   // Temporarily override SHM_OVER and SHM_OVERALL to avoid that file
diff --git a/src/nvim/ex_docmd.c b/src/nvim/ex_docmd.c
index 2913f6d4e9..1b4e83d392 100644
--- a/src/nvim/ex_docmd.c
+++ b/src/nvim/ex_docmd.c
@@ -5334,6 +5334,10 @@ static void ex_resize(exarg_T *eap)
 /// ":find [+command] <file>" command.
 static void ex_find(exarg_T *eap)
 {
+  if (!check_can_set_curbuf_forceit(eap->forceit)) {
+    return;
+  }
+
   char *file_to_find = NULL;
   char *search_ctx = NULL;
   char *fname = find_file_in_path(eap->arg, strlen(eap->arg),
@@ -5364,6 +5368,14 @@ static void ex_find(exarg_T *eap)
 /// ":edit", ":badd", ":balt", ":visual".
 static void ex_edit(exarg_T *eap)
 {
+  // Exclude commands which keep the window's current buffer
+  if (eap->cmdidx != CMD_badd
+      && eap->cmdidx != CMD_balt
+      // All other commands must obey 'winfixbuf' / ! rules
+      && !check_can_set_curbuf_forceit(eap->forceit)) {
+    return;
+  }
+
   do_exedit(eap, NULL);
 }
 
@@ -6670,7 +6682,7 @@ static void ex_checkpath(exarg_T *eap)
 {
   find_pattern_in_path(NULL, 0, 0, false, false, CHECK_PATH, 1,
                        eap->forceit ? ACTION_SHOW_ALL : ACTION_SHOW,
-                       1, (linenr_T)MAXLNUM);
+                       1, (linenr_T)MAXLNUM, eap->forceit);
 }
 
 /// ":psearch"
@@ -6729,7 +6741,7 @@ static void ex_findpat(exarg_T *eap)
   if (!eap->skip) {
     find_pattern_in_path(eap->arg, 0, strlen(eap->arg), whole, !eap->forceit,
                          *eap->cmd == 'd' ? FIND_DEFINE : FIND_ANY,
-                         n, action, eap->line1, eap->line2);
+                         n, action, eap->line1, eap->line2, eap->forceit);
   }
 }
 
diff --git a/src/nvim/globals.h b/src/nvim/globals.h
index 113985cb52..aecb9d1116 100644
--- a/src/nvim/globals.h
+++ b/src/nvim/globals.h
@@ -971,6 +971,9 @@ EXTERN const char e_val_too_large[] INIT(= N_("E1510: Value too large: %s"));
 EXTERN const char e_undobang_cannot_redo_or_move_branch[]
 INIT(= N_("E5767: Cannot use :undo! to redo or move to a different undo branch"));
 
+EXTERN const char e_winfixbuf_cannot_go_to_buffer[]
+INIT(= N_("E1513: Cannot edit buffer. 'winfixbuf' is enabled"));
+
 EXTERN const char e_trustfile[] INIT(= N_("E5570: Cannot update trust file: %s"));
 
 EXTERN const char e_unknown_option2[] INIT(= N_("E355: Unknown option: %s"));
diff --git a/src/nvim/insexpand.c b/src/nvim/insexpand.c
index 41b964323e..d0cd24773f 100644
--- a/src/nvim/insexpand.c
+++ b/src/nvim/insexpand.c
@@ -3027,7 +3027,7 @@ static void get_next_include_file_completion(int compl_type)
                        ((compl_type == CTRL_X_PATH_DEFINES
                          && !(compl_cont_status & CONT_SOL))
                         ? FIND_DEFINE : FIND_ANY),
-                       1, ACTION_EXPAND, 1, MAXLNUM);
+                       1, ACTION_EXPAND, 1, MAXLNUM, false);
 }
 
 /// Get the next set of words matching "compl_pattern" in dictionary or
diff --git a/src/nvim/normal.c b/src/nvim/normal.c
index f586ad6704..aae9621d4a 100644
--- a/src/nvim/normal.c
+++ b/src/nvim/normal.c
@@ -3896,6 +3896,10 @@ static void nv_gotofile(cmdarg_T *cap)
     return;
   }
 
+  if (!check_can_set_curbuf_disabled()) {
+    return;
+  }
+
   char *ptr = grab_file_name(cap->count1, &lnum);
 
   if (ptr != NULL) {
@@ -4232,7 +4236,8 @@ static void nv_brackets(cmdarg_T *cap)
                            (cap->cmdchar == ']'
                             ? curwin->w_cursor.lnum + 1
                             : 1),
-                           MAXLNUM);
+                           MAXLNUM,
+                           false);
       xfree(ptr);
       curwin->w_set_curswant = true;
     }
diff --git a/src/nvim/option.c b/src/nvim/option.c
index 0ac65ed95d..fcc5b5eb06 100644
--- a/src/nvim/option.c
+++ b/src/nvim/option.c
@@ -4629,6 +4629,8 @@ void *get_varp_from(vimoption_T *p, buf_T *buf, win_T *win)
     return &(win->w_p_rnu);
   case PV_NUW:
     return &(win->w_p_nuw);
+  case PV_WFB:
+    return &(win->w_p_wfb);
   case PV_WFH:
     return &(win->w_p_wfh);
   case PV_WFW:
diff --git a/src/nvim/options.lua b/src/nvim/options.lua
index 72f9ff849d..5e8bc1361c 100644
--- a/src/nvim/options.lua
+++ b/src/nvim/options.lua
@@ -8406,6 +8406,8 @@ return {
         		"split" when both are present.
            uselast	If included, jump to the previously used window when
         		jumping to errors with |quickfix| commands.
+        If a window has 'winfixbuf' enabled, 'switchbuf' is currently not
+        applied to the split window.
       ]=],
       expand_cb = 'expand_set_switchbuf',
       full_name = 'switchbuf',
@@ -9817,6 +9819,23 @@ return {
       varname = 'p_window',
     },
     {
+      abbreviation = 'wfb',
+      defaults = { if_true = false },
+      desc = [=[
+        If enabled, the buffer and any window that displays it are paired.
+        For example, attempting to change the buffer with |:edit| will fail.
+        Other commands which change a window's buffer such as |:cnext| will
+        also skip any window with 'winfixbuf' enabled. However if a command
+        has an "!" option, a window can be forced to switch buffers.
+      ]=],
+      full_name = 'winfixbuf',
+      pv_name = 'p_wfb',
+      redraw = { 'current_window' },
+      scope = { 'window' },
+      short_desc = N_('pin a window to a specific buffer'),
+      type = 'boolean',
+    },
+    {
       abbreviation = 'wfh',
       defaults = { if_true = false },
       desc = [=[
diff --git a/src/nvim/quickfix.c b/src/nvim/quickfix.c
index 651ebc9f93..a88b781f32 100644
--- a/src/nvim/quickfix.c
+++ b/src/nvim/quickfix.c
@@ -2699,7 +2699,7 @@ static void qf_goto_win_with_qfl_file(int qf_fnum)
       // Didn't find it, go to the window before the quickfix
       // window, unless 'switchbuf' contains 'uselast': in this case we
       // try to jump to the previously used window first.
-      if ((swb_flags & SWB_USELAST) && win_valid(prevwin)) {
+      if ((swb_flags & SWB_USELAST) && !prevwin->w_p_wfb && win_valid(prevwin)) {
         win = prevwin;
       } else if (altwin != NULL) {
         win = altwin;
@@ -2714,6 +2714,7 @@ static void qf_goto_win_with_qfl_file(int qf_fnum)
     // Remember a usable window.
     if (altwin == NULL
         && !win->w_p_pvw
+        && !win->w_p_wfb
         && bt_normal(win->w_buffer)) {
       altwin = win;
     }
@@ -2802,6 +2803,25 @@ static int qf_jump_edit_buffer(qf_info_T *qi, qfline_T *qf_ptr, int forceit, int
                      ECMD_HIDE + ECMD_SET_HELP,
                      prev_winid == curwin->handle ? curwin : NULL);
   } else {
+    if (!forceit && curwin->w_p_wfb) {
+      if (qi->qfl_type == QFLT_LOCATION) {
+        // Location lists cannot split or reassign their window
+        // so 'winfixbuf' windows must fail
+        semsg("%s", e_winfixbuf_cannot_go_to_buffer);
+        return QF_ABORT;
+      }
+
+      if (!win_valid(prevwin)) {
+        // Split the window, which will be 'nowinfixbuf', and set curwin to that
+        exarg_T new_eap = {
+          .cmdidx = CMD_split,
+          .cmd = "split",
+          .arg = "",
+        };
+        ex_splitview(&new_eap);
+      }
+    }
+
     retval = buflist_getfile(qf_ptr->qf_fnum, 1,
                              GETF_SETMARK | GETF_SWITCH, forceit);
   }
@@ -4297,6 +4317,11 @@ static void qf_jump_first(qf_info_T *qi, unsigned save_qfid, int forceit)
   if (qf_restore_list(qi, save_qfid) == FAIL) {
     return;
   }
+
+  if (!check_can_set_curbuf_forceit(forceit)) {
+    return;
+  }
+
   // Autocommands might have cleared the list, check for that
   if (!qf_list_empty(qf_get_curlist(qi))) {
     qf_jump(qi, 0, 0, forceit);
@@ -5125,7 +5150,7 @@ void ex_cfile(exarg_T *eap)
 
   // This function is used by the :cfile, :cgetfile and :caddfile
   // commands.
-  // :cfile always creates a new quickfix list and jumps to the
+  // :cfile always creates a new quickfix list and may jump to the
   // first error.
   // :cgetfile creates a new quickfix list but doesn't jump to the
   // first error.
@@ -5587,6 +5612,10 @@ theend:
 /// ":lvimgrepadd {pattern} file(s)"
 void ex_vimgrep(exarg_T *eap)
 {
+  if (!check_can_set_curbuf_forceit(eap->forceit)) {
+    return;
+  }
+
   char *au_name = vgr_get_auname(eap->cmdidx);
   if (au_name != NULL && apply_autocmds(EVENT_QUICKFIXCMDPRE, au_name,
                                         curbuf->b_fname, true, curbuf)) {
diff --git a/src/nvim/search.c b/src/nvim/search.c
index 48e41c290d..2fea28ba7c 100644
--- a/src/nvim/search.c
+++ b/src/nvim/search.c
@@ -3564,8 +3564,10 @@ static char *get_line_and_copy(linenr_T lnum, char *buf)
 /// @param action         What to do when we find it
 /// @param start_lnum     first line to start searching
 /// @param end_lnum       last line for searching
+/// @param forceit        If true, always switch to the found path
 void find_pattern_in_path(char *ptr, Direction dir, size_t len, bool whole, bool skip_comments,
-                          int type, int count, int action, linenr_T start_lnum, linenr_T end_lnum)
+                          int type, int count, int action, linenr_T start_lnum, linenr_T end_lnum,
+                          int forceit)
 {
   SearchedFile *files;                  // Stack of included files
   SearchedFile *bigger;                 // When we need more space
@@ -4025,7 +4027,7 @@ search_line:
                 break;
               }
               if (!GETFILE_SUCCESS(getfile(curwin_save->w_buffer->b_fnum, NULL,
-                                           NULL, true, lnum, false))) {
+                                           NULL, true, lnum, forceit))) {
                 break;    // failed to jump to file
               }
             } else {
@@ -4035,7 +4037,7 @@ search_line:
             check_cursor();
           } else {
             if (!GETFILE_SUCCESS(getfile(0, files[depth].name, NULL, true,
-                                         files[depth].lnum, false))) {
+                                         files[depth].lnum, forceit))) {
               break;    // failed to jump to file
             }
             // autocommands may have changed the lnum, we don't
diff --git a/src/nvim/tag.c b/src/nvim/tag.c
index ab5bfc6773..776498fa29 100644
--- a/src/nvim/tag.c
+++ b/src/nvim/tag.c
@@ -290,6 +290,10 @@ void set_buflocal_tfu_callback(buf_T *buf)
 /// @param verbose  print "tag not found" message
 void do_tag(char *tag, int type, int count, int forceit, bool verbose)
 {
+  if (postponed_split == 0 && !check_can_set_curbuf_forceit(forceit)) {
+    return;
+  }
+
   taggy_T *tagstack = curwin->w_tagstack;
   int tagstackidx = curwin->w_tagstackidx;
   int tagstacklen = curwin->w_tagstacklen;
@@ -2784,6 +2788,10 @@ static char *tag_full_fname(tagptrs_T *tagp)
 /// @return  OK for success, NOTAGFILE when file not found, FAIL otherwise.
 static int jumpto_tag(const char *lbuf_arg, int forceit, bool keep_help)
 {
+  if (postponed_split == 0 && !check_can_set_curbuf_forceit(forceit)) {
+    return FAIL;
+  }
+
   char *pbuf_end;
   char *tofree_fname = NULL;
   tagptrs_T tagp;
diff --git a/src/nvim/window.c b/src/nvim/window.c
index ff40a9adef..9f84713ee7 100644
--- a/src/nvim/window.c
+++ b/src/nvim/window.c
@@ -133,6 +133,35 @@ static void log_frame_layout(frame_T *frame)
 }
 #endif
 
+/// Check if the current window is allowed to move to a different buffer.
+///
+/// @return If the window has 'winfixbuf', or this function will return false.
+bool check_can_set_curbuf_disabled(void)
+{
+  if (curwin->w_p_wfb) {
+    semsg("%s", e_winfixbuf_cannot_go_to_buffer);
+    return false;
+  }
+
+  return true;
+}
+
+/// Check if the current window is allowed to move to a different buffer.
+///
+/// @param forceit If true, do not error. If false and 'winfixbuf' is enabled, error.
+///
+/// @return If the window has 'winfixbuf', then forceit must be true
+///     or this function will return false.
+bool check_can_set_curbuf_forceit(int forceit)
+{
+  if (!forceit && curwin->w_p_wfb) {
+    semsg("%s", e_winfixbuf_cannot_go_to_buffer);
+    return false;
+  }
+
+  return true;
+}
+
 /// @return the current window, unless in the cmdline window and "prevwin" is
 /// set, then return "prevwin".
 win_T *prevwin_curwin(void)
@@ -597,7 +626,7 @@ wingotofile:
     ptr = xmemdupz(ptr, len);
 
     find_pattern_in_path(ptr, 0, len, true, Prenum == 0,
-                         type, Prenum1, ACTION_SPLIT, 1, MAXLNUM);
+                         type, Prenum1, ACTION_SPLIT, 1, MAXLNUM, false);
     xfree(ptr);
     curwin->w_set_curswant = true;
     break;
diff --git a/test/functional/options/winfixbuf_spec.lua b/test/functional/options/winfixbuf_spec.lua
new file mode 100644
index 0000000000..20407b9bb7
--- /dev/null
+++ b/test/functional/options/winfixbuf_spec.lua
@@ -0,0 +1,54 @@
+local helpers = require('test.functional.helpers')(after_each)
+local clear = helpers.clear
+local exec_lua = helpers.exec_lua
+
+describe("Nvim API calls with 'winfixbuf'", function()
+  before_each(function()
+    clear()
+  end)
+
+  it("Calling vim.api.nvim_win_set_buf with 'winfixbuf'", function()
+    local results = exec_lua([[
+      local function _setup_two_buffers()
+        local buffer = vim.api.nvim_create_buf(true, true)
+
+        vim.api.nvim_create_buf(true, true)  -- Make another buffer
+
+        local current_window = 0
+        vim.api.nvim_set_option_value("winfixbuf", true, {win=current_window})
+
+        return buffer
+      end
+
+      local other_buffer = _setup_two_buffers()
+      local current_window = 0
+      local results, _ = pcall(vim.api.nvim_win_set_buf, current_window, other_buffer)
+
+      return results
+    ]])
+
+    assert(results == false)
+  end)
+
+  it("Calling vim.api.nvim_set_current_buf with 'winfixbuf'", function()
+    local results = exec_lua([[
+      local function _setup_two_buffers()
+        local buffer = vim.api.nvim_create_buf(true, true)
+
+        vim.api.nvim_create_buf(true, true)  -- Make another buffer
+
+        local current_window = 0
+        vim.api.nvim_set_option_value("winfixbuf", true, {win=current_window})
+
+        return buffer
+      end
+
+      local other_buffer = _setup_two_buffers()
+      local results, _ = pcall(vim.api.nvim_set_current_buf, other_buffer)
+
+      return results
+    ]])
+
+    assert(results == false)
+  end)
+end)
diff --git a/test/old/testdir/test_winfixbuf.vim b/test/old/testdir/test_winfixbuf.vim
new file mode 100644
index 0000000000..2948be7859
--- /dev/null
+++ b/test/old/testdir/test_winfixbuf.vim
@@ -0,0 +1,3131 @@
+" Test 'winfixbuf'
+
+source check.vim
+
+" Find the number of open windows in the current tab
+func s:get_windows_count()
+  return tabpagewinnr(tabpagenr(), '$')
+endfunc
+
+" Create some unnamed buffers.
+func s:make_buffers_list()
+  enew
+  file first
+  let l:first = bufnr()
+
+  enew
+  file middle
+  let l:middle = bufnr()
+
+  enew
+  file last
+  let l:last = bufnr()
+
+  set winfixbuf
+
+  return [l:first, l:last]
+endfunc
+
+" Create some unnamed buffers and add them to an args list
+func s:make_args_list()
+  let [l:first, l:last] = s:make_buffers_list()
+
+  args! first middle last
+
+  return [l:first, l:last]
+endfunc
+
+" Create two buffers and then set the window to 'winfixbuf'
+func s:make_buffer_pairs(...)
+  let l:reversed = get(a:, 1, 0)
+
+  if l:reversed == 1
+    enew
+    file original
+
+    set winfixbuf
+
+    enew!
+    file other
+    let l:other = bufnr()
+
+    return l:other
+  endif
+
+  enew
+  file other
+  let l:other = bufnr()
+
+  enew
+  file current
+
+  set winfixbuf
+
+  return l:other
+endfunc
+
+" Create 3 quick buffers and set the window to 'winfixbuf'
+func s:make_buffer_trio()
+  edit first
+  let l:first = bufnr()
+  edit second
+  let l:second = bufnr()
+
+  set winfixbuf
+
+  edit! third
+  let l:third = bufnr()
+
+  execute ":buffer! " . l:second
+
+  return [l:first, l:second, l:third]
+endfunc
+
+" Create a location list with at least 2 entries + a 'winfixbuf' window.
+func s:make_simple_location_list()
+  enew
+  file middle
+  let l:middle = bufnr()
+  call append(0, ["winfix search-term", "another line"])
+
+  enew!
+  file first
+  let l:first = bufnr()
+  call append(0, "first search-term")
+
+  enew!
+  file last
+  let l:last = bufnr()
+  call append(0, "last search-term")
+
+  call setloclist(
+  \  0,
+  \  [
+  \    {
+  \      "filename": "first",
+  \      "bufnr": l:first,
+  \      "lnum": 1,
+  \    },
+  \    {
+  \      "filename": "middle",
+  \      "bufnr": l:middle,
+  \      "lnum": 1,
+  \    },
+  \    {
+  \      "filename": "middle",
+  \      "bufnr": l:middle,
+  \      "lnum": 2,
+  \    },
+  \    {
+  \      "filename": "last",
+  \      "bufnr": l:last,
+  \      "lnum": 1,
+  \    },
+  \  ]
+  \)
+
+  set winfixbuf
+
+  return [l:first, l:middle, l:last]
+endfunc
+
+" Create a quickfix with at least 2 entries that are in the current 'winfixbuf' window.
+func s:make_simple_quickfix()
+  enew
+  file current
+  let l:current = bufnr()
+  call append(0, ["winfix search-term", "another line"])
+
+  enew!
+  file first
+  let l:first = bufnr()
+  call append(0, "first search-term")
+
+  enew!
+  file last
+  let l:last = bufnr()
+  call append(0, "last search-term")
+
+  call setqflist(
+  \  [
+  \    {
+  \      "filename": "first",
+  \      "bufnr": l:first,
+  \      "lnum": 1,
+  \    },
+  \    {
+  \      "filename": "current",
+  \      "bufnr": l:current,
+  \      "lnum": 1,
+  \    },
+  \    {
+  \      "filename": "current",
+  \      "bufnr": l:current,
+  \      "lnum": 2,
+  \    },
+  \    {
+  \      "filename": "last",
+  \      "bufnr": l:last,
+  \      "lnum": 1,
+  \    },
+  \  ]
+  \)
+
+  set winfixbuf
+
+  return [l:current, l:last]
+endfunc
+
+" Create a quickfix with at least 2 entries that are in the current 'winfixbuf' window.
+func s:make_quickfix_windows()
+  let [l:current, _] = s:make_simple_quickfix()
+  execute "buffer! " . l:current
+
+  split
+  let l:first_window = win_getid()
+  execute "normal \<C-w>j"
+  let l:winfix_window = win_getid()
+
+  " Open the quickfix in a separate split and go to it
+  copen
+  let l:quickfix_window = win_getid()
+
+  return [l:first_window, l:winfix_window, l:quickfix_window]
+endfunc
+
+" Revert all changes that occurred in any past test
+func s:reset_all_buffers()
+  %bwipeout!
+  set nowinfixbuf
+
+  call setqflist([])
+
+  for l:window_info in getwininfo()
+    call setloclist(l:window_info["winid"], [])
+  endfor
+
+  delmarks A-Z0-9
+endfunc
+
+" Find and set the first quickfix entry that points to `buffer`
+func s:set_quickfix_by_buffer(buffer)
+  let l:index = 1  " quickfix indices start at 1
+  for l:entry in getqflist()
+    if l:entry["bufnr"] == a:buffer
+      execute l:index . "cc"
+
+      return
+    endif
+
+    let l:index += 1
+  endfor
+
+  echoerr 'No quickfix entry matching "' . a:buffer . '" could be found.'
+endfunc
+
+" Fail to call :Next on a 'winfixbuf' window unless :Next! is used.
+func Test_Next()
+  call s:reset_all_buffers()
+
+  let [l:first, _] = s:make_args_list()
+  next!
+
+  call assert_fails("Next", "E1513:")
+  call assert_notequal(l:first, bufnr())
+
+  Next!
+  call assert_equal(l:first, bufnr())
+endfunc
+
+" Call :argdo and choose the next available 'nowinfixbuf' window.
+func Test_argdo_choose_available_window()
+  call s:reset_all_buffers()
+
+  let [_, l:last] = s:make_args_list()
+
+  " Make a split window that is 'nowinfixbuf' but make it the second-to-last
+  " window so that :argdo will first try the 'winfixbuf' window, pass over it,
+  " and prefer the other 'nowinfixbuf' window, instead.
+  "
+  " +-------------------+
+  " |   'nowinfixbuf'   |
+  " +-------------------+
+  " |    'winfixbuf'    |  <-- Cursor is here
+  " +-------------------+
+  split
+  let l:nowinfixbuf_window = win_getid()
+  " Move to the 'winfixbuf' window now
+  execute "normal \<C-w>j"
+  let l:winfixbuf_window = win_getid()
+  let l:expected_windows = s:get_windows_count()
+
+  argdo echo ''
+  call assert_equal(l:nowinfixbuf_window, win_getid())
+  call assert_equal(l:last, bufnr())
+  call assert_equal(l:expected_windows, s:get_windows_count())
+endfunc
+
+" Call :argdo and create a new split window if all available windows are 'winfixbuf'.
+func Test_argdo_make_new_window()
+  call s:reset_all_buffers()
+
+  let [l:first, l:last] = s:make_args_list()
+  let l:current = win_getid()
+  let l:current_windows = s:get_windows_count()
+
+  argdo echo ''
+  call assert_notequal(l:current, win_getid())
+  call assert_equal(l:last, bufnr())
+  execute "normal \<C-w>j"
+  call assert_equal(l:first, bufnr())
+  call assert_equal(l:current_windows + 1, s:get_windows_count())
+endfunc
+
+" Fail :argedit but :argedit! is allowed
+func Test_argedit()
+  call s:reset_all_buffers()
+
+  args! first middle last
+  enew
+  file first
+  let l:first = bufnr()
+
+  enew
+  file middle
+  let l:middle = bufnr()
+
+  enew
+  file last
+  let l:last = bufnr()
+
+  set winfixbuf
+
+  let l:current = bufnr()
+  call assert_fails("argedit first middle last", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  argedit! first middle last
+  call assert_equal(l:first, bufnr())
+endfunc
+
+" Fail :arglocal but :arglocal! is allowed
+func Test_arglocal()
+  call s:reset_all_buffers()
+
+  let l:other = s:make_buffer_pairs()
+  let l:current = bufnr()
+  argglobal! other
+  execute "buffer! " . l:current
+
+  call assert_fails("arglocal other", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  arglocal! other
+  call assert_equal(l:other, bufnr())
+endfunc
+
+" Fail :argglobal but :argglobal! is allowed
+func Test_argglobal()
+  call s:reset_all_buffers()
+
+  let l:other = s:make_buffer_pairs()
+  let l:current = bufnr()
+
+  call assert_fails("argglobal other", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  argglobal! other
+  call assert_equal(l:other, bufnr())
+endfunc
+
+" Fail :args but :args! is allowed
+func Test_args()
+  call s:reset_all_buffers()
+
+  let [l:first, _] = s:make_buffers_list()
+  let l:current = bufnr()
+
+  call assert_fails("args first middle last", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  args! first middle last
+  call assert_equal(l:first, bufnr())
+endfunc
+
+" Fail :bNext but :bNext! is allowed
+func Test_bNext()
+  call s:reset_all_buffers()
+
+  let l:other = s:make_buffer_pairs()
+  call assert_fails("bNext", "E1513:")
+  let l:current = bufnr()
+
+  call assert_equal(l:current, bufnr())
+
+  bNext!
+  call assert_equal(l:other, bufnr())
+endfunc
+
+" Allow :badd because it doesn't actually change the current window's buffer
+func Test_badd()
+  call s:reset_all_buffers()
+
+  call s:make_buffer_pairs()
+  let l:current = bufnr()
+
+  badd other
+  call assert_equal(l:current, bufnr())
+endfunc
+
+" Allow :balt because it doesn't actually change the current window's buffer
+func Test_balt()
+  call s:reset_all_buffers()
+
+  call s:make_buffer_pairs()
+  let l:current = bufnr()
+
+  balt other
+  call assert_equal(l:current, bufnr())
+endfunc
+
+" Fail :bfirst but :bfirst! is allowed
+func Test_bfirst()
+  call s:reset_all_buffers()
+
+  let l:other = s:make_buffer_pairs()
+  let l:current = bufnr()
+
+  call assert_fails("bfirst", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  bfirst!
+  call assert_equal(l:other, bufnr())
+endfunc
+
+" Fail :blast but :blast! is allowed
+func Test_blast()
+  call s:reset_all_buffers()
+
+  let l:other = s:make_buffer_pairs(1)
+  bfirst!
+  let l:current = bufnr()
+
+  call assert_fails("blast", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  blast!
+  call assert_equal(l:other, bufnr())
+endfunc
+
+" Fail :bmodified but :bmodified! is allowed
+func Test_bmodified()
+  call s:reset_all_buffers()
+
+  let l:other = s:make_buffer_pairs()
+  let l:current = bufnr()
+
+  execute "buffer! " . l:other
+  set modified
+  execute "buffer! " . l:current
+
+  call assert_fails("bmodified", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  bmodified!
+  call assert_equal(l:other, bufnr())
+endfunc
+
+" Fail :bnext but :bnext! is allowed
+func Test_bnext()
+  call s:reset_all_buffers()
+
+  let l:other = s:make_buffer_pairs()
+  let l:current = bufnr()
+
+  call assert_fails("bnext", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  bnext!
+  call assert_equal(l:other, bufnr())
+endfunc
+
+" Fail :bprevious but :bprevious! is allowed
+func Test_bprevious()
+  call s:reset_all_buffers()
+
+  let l:other = s:make_buffer_pairs()
+  let l:current = bufnr()
+
+  call assert_fails("bprevious", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  bprevious!
+  call assert_equal(l:other, bufnr())
+endfunc
+
+" Fail :brewind but :brewind! is allowed
+func Test_brewind()
+  call s:reset_all_buffers()
+
+  let l:other = s:make_buffer_pairs()
+  let l:current = bufnr()
+
+  call assert_fails("brewind", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  brewind!
+  call assert_equal(l:other, bufnr())
+endfunc
+
+" Fail :browse edit but :browse edit! is allowed
+func Test_browse_edit_fail()
+  call s:reset_all_buffers()
+
+  let l:other = s:make_buffer_pairs()
+  let l:current = bufnr()
+
+  call assert_fails("browse edit other", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  browse edit! other
+  call assert_equal(l:other, bufnr())
+endfunc
+
+" Allow :browse w because it doesn't change the buffer in the current file
+func Test_browse_edit_pass()
+  call s:reset_all_buffers()
+
+  let l:other = s:make_buffer_pairs()
+  let l:current = bufnr()
+
+  browse write other
+
+  call delete("other")
+endfunc
+
+" Call :bufdo and choose the next available 'nowinfixbuf' window.
+func Test_bufdo_choose_available_window()
+  call s:reset_all_buffers()
+
+  let l:other = s:make_buffer_pairs()
+
+  " Make a split window that is 'nowinfixbuf' but make it the second-to-last
+  " window so that :bufdo will first try the 'winfixbuf' window, pass over it,
+  " and prefer the other 'nowinfixbuf' window, instead.
+  "
+  " +-------------------+
+  " |   'nowinfixbuf'   |
+  " +-------------------+
+  " |    'winfixbuf'    |  <-- Cursor is here
+  " +-------------------+
+  split
+  let l:nowinfixbuf_window = win_getid()
+  " Move to the 'winfixbuf' window now
+  execute "normal \<C-w>j"
+  let l:winfixbuf_window = win_getid()
+
+  let l:current = bufnr()
+  let l:expected_windows = s:get_windows_count()
+
+  call assert_notequal(l:current, l:other)
+
+  bufdo echo ''
+  call assert_equal(l:nowinfixbuf_window, win_getid())
+  call assert_notequal(l:other, bufnr())
+  call assert_equal(l:expected_windows, s:get_windows_count())
+endfunc
+
+" Call :bufdo and create a new split window if all available windows are 'winfixbuf'.
+func Test_bufdo_make_new_window()
+  call s:reset_all_buffers()
+
+  let [l:first, l:last] = s:make_buffers_list()
+  execute "buffer! " . l:first
+  let l:current = win_getid()
+  let l:current_windows = s:get_windows_count()
+
+  bufdo echo ''
+  call assert_notequal(l:current, win_getid())
+  call assert_equal(l:last, bufnr())
+  execute "normal \<C-w>j"
+  call assert_equal(l:first, bufnr())
+  call assert_equal(l:current_windows + 1, s:get_windows_count())
+endfunc
+
+" Fail :buffer but :buffer! is allowed
+func Test_buffer()
+  call s:reset_all_buffers()
+
+  let l:other = s:make_buffer_pairs()
+  let l:current = bufnr()
+
+  call assert_fails("buffer " . l:other, "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  execute "buffer! " . l:other
+  call assert_equal(l:other, bufnr())
+endfunc
+
+" Allow :buffer on a 'winfixbuf' window if there is no change in buffer
+func Test_buffer_same_buffer()
+  call s:reset_all_buffers()
+
+  call s:make_buffer_pairs()
+  let l:current = bufnr()
+
+  execute "buffer " . l:current
+  call assert_equal(l:current, bufnr())
+
+  execute "buffer! " . l:current
+  call assert_equal(l:current, bufnr())
+endfunc
+
+" Allow :cNext but the 'nowinfixbuf' window is selected, instead
+func Test_cNext()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let [l:first_window, l:winfix_window, l:quickfix_window] = s:make_quickfix_windows()
+
+  " The call to `:cNext` succeeds but it selects the window with 'nowinfixbuf' instead
+  call s:set_quickfix_by_buffer(winbufnr(l:winfix_window))
+
+  " Make sure the previous window has 'winfixbuf' so we can test that our
+  " "skip 'winfixbuf' window" logic works.
+  call win_gotoid(l:winfix_window)
+  call win_gotoid(l:quickfix_window)
+
+  cNext
+  call assert_equal(l:first_window, win_getid())
+endfunc
+
+" Allow :cNfile but the 'nowinfixbuf' window is selected, instead
+func Test_cNfile()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let [l:first_window, l:winfix_window, l:quickfix_window] = s:make_quickfix_windows()
+
+  " The call to `:cNfile` succeeds but it selects the window with 'nowinfixbuf' instead
+  call s:set_quickfix_by_buffer(winbufnr(l:winfix_window))
+  cnext!
+
+  " Make sure the previous window has 'winfixbuf' so we can test that our
+  " "skip 'winfixbuf' window" logic works.
+  call win_gotoid(l:winfix_window)
+  call win_gotoid(l:quickfix_window)
+
+  cNfile
+  call assert_equal(l:first_window, win_getid())
+endfunc
+
+" Allow :caddexpr because it doesn't change the current buffer
+func Test_caddexpr()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let l:file_path = tempname()
+  call writefile(["Error - bad-thing-found"], l:file_path)
+  execute "edit " . l:file_path
+  let l:file_buffer = bufnr()
+  let l:current = bufnr()
+
+  edit first.unittest
+  call append(0, ["some-search-term bad-thing-found"])
+
+  edit! other.unittest
+
+  set winfixbuf
+
+  execute "buffer! " . l:file_buffer
+
+  execute 'caddexpr expand("%") .. ":" .. line(".") .. ":" .. getline(".")'
+  call assert_equal(l:current, bufnr())
+
+  call delete(l:file_path)
+endfunc
+
+" Fail :cbuffer but :cbuffer! is allowed
+func Test_cbuffer()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let l:file_path = tempname()
+  call writefile(["first.unittest:1:Error - bad-thing-found"], l:file_path)
+  execute "edit " . l:file_path
+  let l:file_buffer = bufnr()
+  let l:current = bufnr()
+
+  edit first.unittest
+  call append(0, ["some-search-term bad-thing-found"])
+
+  edit! other.unittest
+
+  set winfixbuf
+
+  execute "buffer! " . l:file_buffer
+
+  call assert_fails("cbuffer " . l:file_buffer)
+  call assert_equal(l:current, bufnr())
+
+  execute "cbuffer! " . l:file_buffer
+  call assert_equal("first.unittest", expand("%:t"))
+
+  call delete(l:file_path)
+endfunc
+
+" Allow :cc but the 'nowinfixbuf' window is selected, instead
+func Test_cc()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let [l:first_window, l:winfix_window, l:quickfix_window] = s:make_quickfix_windows()
+
+  " The call to `:cnext` succeeds but it selects the window with 'nowinfixbuf' instead
+  call s:set_quickfix_by_buffer(winbufnr(l:winfix_window))
+
+  " Make sure the previous window has 'winfixbuf' so we can test that our
+  " "skip 'winfixbuf' window" logic works.
+  call win_gotoid(l:winfix_window)
+  call win_gotoid(l:quickfix_window)
+  " Go up one line in the quickfix window to an quickfix entry that doesn't
+  " point to a winfixbuf buffer
+  normal k
+  " Attempt to make the previous window, winfixbuf buffer, to go to the
+  " non-winfixbuf quickfix entry
+  .cc
+
+  " Confirm that :.cc did not change the winfixbuf-enabled window
+  call assert_equal(l:first_window, win_getid())
+endfunc
+
+" Call :cdo and choose the next available 'nowinfixbuf' window.
+func Test_cdo_choose_available_window()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let [l:current, l:last] = s:make_simple_quickfix()
+  execute "buffer! " . l:current
+
+  " Make a split window that is 'nowinfixbuf' but make it the second-to-last
+  " window so that :cdo will first try the 'winfixbuf' window, pass over it,
+  " and prefer the other 'nowinfixbuf' window, instead.
+  "
+  " +-------------------+
+  " |   'nowinfixbuf'   |
+  " +-------------------+
+  " |    'winfixbuf'    |  <-- Cursor is here
+  " +-------------------+
+  split
+  let l:nowinfixbuf_window = win_getid()
+  " Move to the 'winfixbuf' window now
+  execute "normal \<C-w>j"
+  let l:winfixbuf_window = win_getid()
+  let l:expected_windows = s:get_windows_count()
+
+  cdo echo ''
+
+  call assert_equal(l:nowinfixbuf_window, win_getid())
+  call assert_equal(l:last, bufnr())
+  execute "normal \<C-w>j"
+  call assert_equal(l:current, bufnr())
+  call assert_equal(l:expected_windows, s:get_windows_count())
+endfunc
+
+" Call :cdo and create a new split window if all available windows are 'winfixbuf'.
+func Test_cdo_make_new_window()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let [l:current_buffer, l:last] = s:make_simple_quickfix()
+  execute "buffer! " . l:current_buffer
+
+  let l:current_window = win_getid()
+  let l:current_windows = s:get_windows_count()
+
+  cdo echo ''
+  call assert_notequal(l:current_window, win_getid())
+  call assert_equal(l:last, bufnr())
+  execute "normal \<C-w>j"
+  call assert_equal(l:current_buffer, bufnr())
+  call assert_equal(l:current_windows + 1, s:get_windows_count())
+endfunc
+
+" Fail :cexpr but :cexpr! is allowed
+func Test_cexpr()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let l:file = tempname()
+  let l:entry = '["' . l:file . ':1:bar"]'
+  let l:current = bufnr()
+
+  set winfixbuf
+
+  call assert_fails("cexpr " . l:entry)
+  call assert_equal(l:current, bufnr())
+
+  execute "cexpr! " . l:entry
+  call assert_equal(fnamemodify(l:file, ":t"), expand("%:t"))
+endfunc
+
+" Call :cfdo and choose the next available 'nowinfixbuf' window.
+func Test_cfdo_choose_available_window()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let [l:current, l:last] = s:make_simple_quickfix()
+  execute "buffer! " . l:current
+
+  " Make a split window that is 'nowinfixbuf' but make it the second-to-last
+  " window so that :cfdo will first try the 'winfixbuf' window, pass over it,
+  " and prefer the other 'nowinfixbuf' window, instead.
+  "
+  " +-------------------+
+  " |   'nowinfixbuf'   |
+  " +-------------------+
+  " |    'winfixbuf'    |  <-- Cursor is here
+  " +-------------------+
+  split
+  let l:nowinfixbuf_window = win_getid()
+  " Move to the 'winfixbuf' window now
+  execute "normal \<C-w>j"
+  let l:winfixbuf_window = win_getid()
+  let l:expected_windows = s:get_windows_count()
+
+  cfdo echo ''
+
+  call assert_equal(l:nowinfixbuf_window, win_getid())
+  call assert_equal(l:last, bufnr())
+  execute "normal \<C-w>j"
+  call assert_equal(l:current, bufnr())
+  call assert_equal(l:expected_windows, s:get_windows_count())
+endfunc
+
+" Call :cfdo and create a new split window if all available windows are 'winfixbuf'.
+func Test_cfdo_make_new_window()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let [l:current_buffer, l:last] = s:make_simple_quickfix()
+  execute "buffer! " . l:current_buffer
+
+  let l:current_window = win_getid()
+  let l:current_windows = s:get_windows_count()
+
+  cfdo echo ''
+  call assert_notequal(l:current_window, win_getid())
+  call assert_equal(l:last, bufnr())
+  execute "normal \<C-w>j"
+  call assert_equal(l:current_buffer, bufnr())
+  call assert_equal(l:current_windows + 1, s:get_windows_count())
+endfunc
+
+" Fail :cfile but :cfile! is allowed
+func Test_cfile()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  edit first.unittest
+  call append(0, ["some-search-term bad-thing-found"])
+  write
+  let l:first = bufnr()
+
+  edit! second.unittest
+  call append(0, ["some-search-term"])
+  write
+
+  let l:file = tempname()
+  call writefile(["first.unittest:1:Error - bad-thing-found was detected"], l:file)
+
+  let l:current = bufnr()
+
+  set winfixbuf
+
+  call assert_fails(":cfile " . l:file)
+  call assert_equal(l:current, bufnr())
+
+  execute ":cfile! " . l:file
+  call assert_equal(l:first, bufnr())
+
+  call delete(l:file)
+  call delete("first.unittest")
+  call delete("second.unittest")
+endfunc
+
+" Allow :cfirst but the 'nowinfixbuf' window is selected, instead
+func Test_cfirst()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let [l:first_window, l:winfix_window, l:quickfix_window] = s:make_quickfix_windows()
+
+  " The call to `:cfirst` succeeds but it selects the window with 'nowinfixbuf' instead
+  call s:set_quickfix_by_buffer(winbufnr(l:winfix_window))
+
+  " Make sure the previous window has 'winfixbuf' so we can test that our
+  " "skip 'winfixbuf' window" logic works.
+  call win_gotoid(l:winfix_window)
+  call win_gotoid(l:quickfix_window)
+
+  cfirst
+  call assert_equal(l:first_window, win_getid())
+endfunc
+
+" Allow :clast but the 'nowinfixbuf' window is selected, instead
+func Test_clast()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let [l:first_window, l:winfix_window, l:quickfix_window] = s:make_quickfix_windows()
+
+  " The call to `:clast` succeeds but it selects the window with 'nowinfixbuf' instead
+  call s:set_quickfix_by_buffer(winbufnr(l:winfix_window))
+
+  " Make sure the previous window has 'winfixbuf' so we can test that our
+  " "skip 'winfixbuf' window" logic works.
+  call win_gotoid(l:winfix_window)
+  call win_gotoid(l:quickfix_window)
+
+  clast
+  call assert_equal(l:first_window, win_getid())
+endfunc
+
+" Allow :cnext but the 'nowinfixbuf' window is selected, instead
+" Make sure no new windows are created and previous windows are reused
+func Test_cnext()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let [l:first_window, l:winfix_window, l:quickfix_window] = s:make_quickfix_windows()
+  let l:expected = s:get_windows_count()
+
+  " The call to `:cnext` succeeds but it selects the window with 'nowinfixbuf' instead
+  call s:set_quickfix_by_buffer(winbufnr(l:winfix_window))
+
+  cnext!
+  call assert_equal(l:expected, s:get_windows_count())
+
+  " Make sure the previous window has 'winfixbuf' so we can test that our
+  " "skip 'winfixbuf' window" logic works.
+  call win_gotoid(l:winfix_window)
+  call win_gotoid(l:quickfix_window)
+
+  cnext
+  call assert_equal(l:first_window, win_getid())
+  call assert_equal(l:expected, s:get_windows_count())
+endfunc
+
+" Make sure :cnext creates a split window if no previous window exists
+func Test_cnext_no_previous_window()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let [l:current, _] = s:make_simple_quickfix()
+  execute "buffer! " . l:current
+
+  let l:expected = s:get_windows_count()
+
+  " Open the quickfix in a separate split and go to it
+  copen
+
+  call assert_equal(l:expected + 1, s:get_windows_count())
+endfunc
+
+" Allow :cnext and create a 'nowinfixbuf' window if none exists
+func Test_cnext_make_new_window()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let [l:current, _] = s:make_simple_quickfix()
+  let l:current = win_getid()
+
+  cfirst!
+
+  let l:windows = s:get_windows_count()
+  let l:expected = l:windows + 1  " We're about to create a new split window
+
+  cnext
+  call assert_equal(l:expected, s:get_windows_count())
+
+  cnext!
+  call assert_equal(l:expected, s:get_windows_count())
+endfunc
+
+" Allow :cprevious but the 'nowinfixbuf' window is selected, instead
+func Test_cprevious()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let [l:first_window, l:winfix_window, l:quickfix_window] = s:make_quickfix_windows()
+
+  " The call to `:cprevious` succeeds but it selects the window with 'nowinfixbuf' instead
+  call s:set_quickfix_by_buffer(winbufnr(l:winfix_window))
+
+  " Make sure the previous window has 'winfixbuf' so we can test that our
+  " "skip 'winfixbuf' window" logic works.
+  call win_gotoid(l:winfix_window)
+  call win_gotoid(l:quickfix_window)
+
+  cprevious
+  call assert_equal(l:first_window, win_getid())
+endfunc
+
+" Allow :cnfile but the 'nowinfixbuf' window is selected, instead
+func Test_cnfile()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let [l:first_window, l:winfix_window, l:quickfix_window] = s:make_quickfix_windows()
+
+  " The call to `:cnfile` succeeds but it selects the window with 'nowinfixbuf' instead
+  call s:set_quickfix_by_buffer(winbufnr(l:winfix_window))
+  cnext!
+
+  " Make sure the previous window has 'winfixbuf' so we can test that our
+  " "skip 'winfixbuf' window" logic works.
+  call win_gotoid(l:winfix_window)
+  call win_gotoid(l:quickfix_window)
+
+  cnfile
+  call assert_equal(l:first_window, win_getid())
+endfunc
+
+" Allow :cpfile but the 'nowinfixbuf' window is selected, instead
+func Test_cpfile()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let [l:first_window, l:winfix_window, l:quickfix_window] = s:make_quickfix_windows()
+
+  " The call to `:cpfile` succeeds but it selects the window with 'nowinfixbuf' instead
+  call s:set_quickfix_by_buffer(winbufnr(l:winfix_window))
+  cnext!
+
+  " Make sure the previous window has 'winfixbuf' so we can test that our
+  " "skip 'winfixbuf' window" logic works.
+  call win_gotoid(l:winfix_window)
+  call win_gotoid(l:quickfix_window)
+
+  cpfile
+  call assert_equal(l:first_window, win_getid())
+endfunc
+
+" Allow :crewind but the 'nowinfixbuf' window is selected, instead
+func Test_crewind()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let [l:first_window, l:winfix_window, l:quickfix_window] = s:make_quickfix_windows()
+
+  " The call to `:crewind` succeeds but it selects the window with 'nowinfixbuf' instead
+  call s:set_quickfix_by_buffer(winbufnr(l:winfix_window))
+  cnext!
+
+  " Make sure the previous window has 'winfixbuf' so we can test that our
+  " "skip 'winfixbuf' window" logic works.
+  call win_gotoid(l:winfix_window)
+  call win_gotoid(l:quickfix_window)
+
+  crewind
+  call assert_equal(l:first_window, win_getid())
+endfunc
+
+" Allow <C-w>f because it opens in a new split
+func Test_ctrl_w_f()
+  call s:reset_all_buffers()
+
+  enew
+  let l:file_name = tempname()
+  call writefile([], l:file_name)
+  let l:file_buffer = bufnr()
+
+  enew
+  file other
+  let l:other_buffer = bufnr()
+
+  set winfixbuf
+
+  call setline(1, l:file_name)
+  let l:current_windows = s:get_windows_count()
+  execute "normal \<C-w>f"
+
+  call assert_equal(l:current_windows + 1, s:get_windows_count())
+
+  call delete(l:file_name)
+endfunc
+
+" Fail :djump but :djump! is allowed
+func Test_djump()
+  call s:reset_all_buffers()
+
+  let l:include_file = tempname() . ".h"
+  call writefile(["min(1, 12);",
+        \ '#include "' . l:include_file . '"'
+        \ ],
+        \ "main.c")
+  call writefile(["#define min(X, Y)  ((X) < (Y) ? (X) : (Y))"], l:include_file)
+  edit main.c
+
+  set winfixbuf
+
+  let l:current = bufnr()
+
+  call assert_fails("djump 1 /min/", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  djump! 1 /min/
+  call assert_notequal(l:current, bufnr())
+
+  call delete("main.c")
+  call delete(l:include_file)
+endfunc
+
+" Fail :drop but :drop! is allowed
+func Test_drop()
+  call s:reset_all_buffers()
+
+  let l:other = s:make_buffer_pairs()
+  let l:current = bufnr()
+
+  call assert_fails("drop other", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  drop! other
+  call assert_equal(l:other, bufnr())
+endfunc
+
+" Fail :edit but :edit! is allowed
+func Test_edit()
+  call s:reset_all_buffers()
+
+  let l:other = s:make_buffer_pairs()
+  let l:current = bufnr()
+
+  call assert_fails("edit other", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  edit! other
+  call assert_equal(l:other, bufnr())
+endfunc
+
+" Fail :enew but :enew! is allowed
+func Test_enew()
+  call s:reset_all_buffers()
+
+  let l:other = s:make_buffer_pairs()
+  let l:current = bufnr()
+
+  call assert_fails("enew", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  enew!
+  call assert_notequal(l:other, bufnr())
+  call assert_notequal(3, bufnr())
+endfunc
+
+" Fail :ex but :ex! is allowed
+func Test_ex()
+  call s:reset_all_buffers()
+
+  let l:other = s:make_buffer_pairs()
+  let l:current = bufnr()
+
+  call assert_fails("ex other", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  ex! other
+  call assert_equal(l:other, bufnr())
+endfunc
+
+" Fail :find but :find! is allowed
+func Test_find()
+  call s:reset_all_buffers()
+
+  let l:current = bufnr()
+  let l:file = tempname()
+  call writefile([], l:file)
+  let l:directory = fnamemodify(l:file, ":p:h")
+  let l:name = fnamemodify(l:file, ":p:t")
+
+  let l:original_path = &path
+  execute "set path=" . l:directory
+
+  set winfixbuf
+
+  call assert_fails("execute 'find " . l:name . "'", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  execute "find! " . l:name
+  call assert_equal(l:file, expand("%:p"))
+
+  execute "set path=" . l:original_path
+  call delete(l:file)
+endfunc
+
+" Fail :first but :first! is allowed
+func Test_first()
+  call s:reset_all_buffers()
+
+  let [l:first, _] = s:make_args_list()
+  next!
+
+  call assert_fails("first", "E1513:")
+  call assert_notequal(l:first, bufnr())
+
+  first!
+  call assert_equal(l:first, bufnr())
+endfunc
+
+" Fail :grep but :grep! is allowed
+func Test_grep()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  edit first.unittest
+  call append(0, ["some-search-term"])
+  write
+  let l:first = bufnr()
+
+  edit current.unittest
+  call append(0, ["some-search-term"])
+  write
+  let l:current = bufnr()
+
+  edit! last.unittest
+  call append(0, ["some-search-term"])
+  write
+  let l:last = bufnr()
+
+  set winfixbuf
+
+  buffer! current.unittest
+
+  call assert_fails("silent! grep some-search-term *.unittest", "E1513:")
+  call assert_equal(l:current, bufnr())
+  execute "edit! " . l:first
+
+  silent! grep! some-search-term *.unittest
+  call assert_notequal(l:first, bufnr())
+
+  call delete("first.unittest")
+  call delete("current.unittest")
+  call delete("last.unittest")
+endfunc
+
+" Fail :ijump but :ijump! is allowed
+func Test_ijump()
+  call s:reset_all_buffers()
+
+  let l:include_file = tempname() . ".h"
+  call writefile([
+        \ '#include "' . l:include_file . '"'
+        \ ],
+        \ "main.c")
+  call writefile(["#define min(X, Y)  ((X) < (Y) ? (X) : (Y))"], l:include_file)
+  edit main.c
+
+  set winfixbuf
+
+  let l:current = bufnr()
+
+  set define=^\\s*#\\s*define
+  set include=^\\s*#\\s*include
+  set path=.,/usr/include,,
+
+  call assert_fails("ijump /min/", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  set nowinfixbuf
+
+  ijump! /min/
+  call assert_notequal(l:current, bufnr())
+
+  set define&
+  set include&
+  set path&
+  call delete("main.c")
+  call delete(l:include_file)
+endfunc
+
+" Fail :lNext but :lNext! is allowed
+func Test_lNext()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let [l:first, l:middle, _] = s:make_simple_location_list()
+  lnext!
+
+  call assert_fails("lNext", "E1513:")
+  call assert_equal(l:middle, bufnr())
+
+  lnext!  " Reset for the next test
+
+  lNext!
+  call assert_equal(l:first, bufnr())
+endfunc
+
+" Fail :lNfile but :lNfile! is allowed
+func Test_lNfile()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let [l:first, l:current, _] = s:make_simple_location_list()
+  lnext!
+
+  call assert_fails("lNfile", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  lnext!  " Reset for the next test
+
+  lNfile!
+  call assert_equal(l:first, bufnr())
+endfunc
+
+" Allow :laddexpr because it doesn't change the current buffer
+func Test_laddexpr()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let l:file_path = tempname()
+  call writefile(["Error - bad-thing-found"], l:file_path)
+  execute "edit " . l:file_path
+  let l:file_buffer = bufnr()
+  let l:current = bufnr()
+
+  edit first.unittest
+  call append(0, ["some-search-term bad-thing-found"])
+
+  edit! other.unittest
+
+  set winfixbuf
+
+  execute "buffer! " . l:file_buffer
+
+  execute 'laddexpr expand("%") .. ":" .. line(".") .. ":" .. getline(".")'
+  call assert_equal(l:current, bufnr())
+
+  call delete(l:file_path)
+endfunc
+
+" Fail :last but :last! is allowed
+func Test_last()
+  call s:reset_all_buffers()
+
+  let [_, l:last] = s:make_args_list()
+  next!
+
+  call assert_fails("last", "E1513:")
+  call assert_notequal(l:last, bufnr())
+
+  last!
+  call assert_equal(l:last, bufnr())
+endfunc
+
+" Fail :lbuffer but :lbuffer! is allowed
+func Test_lbuffer()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let l:file_path = tempname()
+  call writefile(["first.unittest:1:Error - bad-thing-found"], l:file_path)
+  execute "edit " . l:file_path
+  let l:file_buffer = bufnr()
+  let l:current = bufnr()
+
+  edit first.unittest
+  call append(0, ["some-search-term bad-thing-found"])
+
+  edit! other.unittest
+
+  set winfixbuf
+
+  execute "buffer! " . l:file_buffer
+
+  call assert_fails("lbuffer " . l:file_buffer)
+  call assert_equal(l:current, bufnr())
+
+  execute "lbuffer! " . l:file_buffer
+  call assert_equal("first.unittest", expand("%:t"))
+
+  call delete(l:file_path)
+endfunc
+
+" Fail :ldo but :ldo! is allowed
+func Test_ldo()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let [l:first, l:middle, l:last] = s:make_simple_location_list()
+  lnext!
+
+  call assert_fails('execute "ldo buffer ' . l:first . '"', "E1513:")
+  call assert_equal(l:middle, bufnr())
+  execute "ldo! buffer " . l:first
+  call assert_notequal(l:last, bufnr())
+endfunc
+
+" Fail :lfdo but :lfdo! is allowed
+func Test_lexpr()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let l:file = tempname()
+  let l:entry = '["' . l:file . ':1:bar"]'
+  let l:current = bufnr()
+
+  set winfixbuf
+
+  call assert_fails("lexpr " . l:entry)
+  call assert_equal(l:current, bufnr())
+
+  execute "lexpr! " . l:entry
+  call assert_equal(fnamemodify(l:file, ":t"), expand("%:t"))
+endfunc
+
+" Fail :lfdo but :lfdo! is allowed
+func Test_lfdo()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let [l:first, l:middle, l:last] = s:make_simple_location_list()
+  lnext!
+
+  call assert_fails('execute "lfdo buffer ' . l:first . '"', "E1513:")
+  call assert_equal(l:middle, bufnr())
+  execute "lfdo! buffer " . l:first
+  call assert_notequal(l:last, bufnr())
+endfunc
+
+" Fail :lfile but :lfile! is allowed
+func Test_lfile()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  edit first.unittest
+  call append(0, ["some-search-term bad-thing-found"])
+  write
+  let l:first = bufnr()
+
+  edit! second.unittest
+  call append(0, ["some-search-term"])
+  write
+
+  let l:file = tempname()
+  call writefile(["first.unittest:1:Error - bad-thing-found was detected"], l:file)
+
+  let l:current = bufnr()
+
+  set winfixbuf
+
+  call assert_fails(":lfile " . l:file)
+  call assert_equal(l:current, bufnr())
+
+  execute ":lfile! " . l:file
+  call assert_equal(l:first, bufnr())
+
+  call delete(l:file)
+  call delete("first.unittest")
+  call delete("second.unittest")
+endfunc
+
+" Fail :ll but :ll! is allowed
+func Test_ll()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let [l:first, l:middle, l:last] = s:make_simple_location_list()
+  lopen
+  lfirst!
+  execute "normal \<C-w>j"
+  normal j
+
+  call assert_fails(".ll", "E1513:")
+  execute "normal \<C-w>k"
+  call assert_equal(l:first, bufnr())
+  execute "normal \<C-w>j"
+  .ll!
+  execute "normal \<C-w>k"
+  call assert_equal(l:middle, bufnr())
+endfunc
+
+" Fail :llast but :llast! is allowed
+func Test_llast()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let [l:first, _, l:last] = s:make_simple_location_list()
+  lfirst!
+
+  call assert_fails("llast", "E1513:")
+  call assert_equal(l:first, bufnr())
+
+  llast!
+  call assert_equal(l:last, bufnr())
+endfunc
+
+" Fail :lnext but :lnext! is allowed
+func Test_lnext()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let [l:first, l:middle, l:last] = s:make_simple_location_list()
+  ll!
+
+  call assert_fails("lnext", "E1513:")
+  call assert_equal(l:first, bufnr())
+
+  lnext!
+  call assert_equal(l:middle, bufnr())
+endfunc
+
+" Fail :lnfile but :lnfile! is allowed
+func Test_lnfile()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let [_, l:current, l:last] = s:make_simple_location_list()
+  lnext!
+
+  call assert_fails("lnfile", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  lprevious!  " Reset for the next test call
+
+  lnfile!
+  call assert_equal(l:last, bufnr())
+endfunc
+
+" Fail :lpfile but :lpfile! is allowed
+func Test_lpfile()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let [l:first, l:current, _] = s:make_simple_location_list()
+  lnext!
+
+  call assert_fails("lpfile", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  lnext!  " Reset for the next test call
+
+  lpfile!
+  call assert_equal(l:first, bufnr())
+endfunc
+
+" Fail :lprevious but :lprevious! is allowed
+func Test_lprevious()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let [l:first, l:middle, _] = s:make_simple_location_list()
+  lnext!
+
+  call assert_fails("lprevious", "E1513:")
+  call assert_equal(l:middle, bufnr())
+
+  lnext!  " Reset for the next test call
+
+  lprevious!
+  call assert_equal(l:first, bufnr())
+endfunc
+
+" Fail :lrewind but :lrewind! is allowed
+func Test_lrewind()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  let [l:first, l:middle, _] = s:make_simple_location_list()
+  lnext!
+
+  call assert_fails("lrewind", "E1513:")
+  call assert_equal(l:middle, bufnr())
+
+  lrewind!
+  call assert_equal(l:first, bufnr())
+endfunc
+
+" Fail :ltag but :ltag! is allowed
+func Test_ltag()
+  call s:reset_all_buffers()
+
+  set tags=Xtags
+  call writefile(["!_TAG_FILE_ENCODING\tutf-8\t//",
+        \ "one\tXfile\t1",
+        \ "three\tXfile\t3",
+        \ "two\tXfile\t2"],
+        \ "Xtags")
+  call writefile(["one", "two", "three"], "Xfile")
+  call writefile(["one"], "Xother")
+  edit Xother
+  execute "normal \<C-]>"
+
+  set winfixbuf
+
+  let l:current = bufnr()
+
+  call assert_fails("ltag one", "E1513:")
+
+  ltag! one
+
+  set tags&
+  call delete("Xtags")
+  call delete("Xfile")
+  call delete("Xother")
+endfunc
+
+" Fail vim.cmd if we try to change buffers while 'winfixbuf' is set
+func Test_lua_command()
+  call s:reset_all_buffers()
+
+  enew
+  file first
+  let l:previous = bufnr()
+
+  enew
+  file second
+  let l:current = bufnr()
+
+  set winfixbuf
+
+  call assert_fails('lua vim.cmd("buffer " .. ' . l:previous . ')')
+  call assert_equal(l:current, bufnr())
+
+  execute 'lua vim.cmd("buffer! " .. ' . l:previous . ')'
+  call assert_equal(l:previous, bufnr())
+endfunc
+
+" Fail :lvimgrep but :lvimgrep! is allowed
+func Test_lvimgrep()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  edit first.unittest
+  call append(0, ["some-search-term"])
+  write
+
+  edit winfix.unittest
+  call append(0, ["some-search-term"])
+  write
+  let l:current = bufnr()
+
+  set winfixbuf
+
+  edit! last.unittest
+  call append(0, ["some-search-term"])
+  write
+  let l:last = bufnr()
+
+  buffer! winfix.unittest
+
+  call assert_fails("lvimgrep /some-search-term/ *.unittest", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  lvimgrep! /some-search-term/ *.unittest
+  call assert_notequal(l:current, bufnr())
+
+  call delete("first.unittest")
+  call delete("winfix.unittest")
+  call delete("last.unittest")
+endfunc
+
+" Fail :lvimgrepadd but :lvimgrepadd! is allowed
+func Test_lvimgrepadd()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  edit first.unittest
+  call append(0, ["some-search-term"])
+  write
+
+  edit winfix.unittest
+  call append(0, ["some-search-term"])
+  write
+  let l:current = bufnr()
+
+  set winfixbuf
+
+  edit! last.unittest
+  call append(0, ["some-search-term"])
+  write
+  let l:last = bufnr()
+
+  buffer! winfix.unittest
+
+  call assert_fails("lvimgrepadd /some-search-term/ *.unittest")
+  call assert_equal(l:current, bufnr())
+
+  lvimgrepadd! /some-search-term/ *.unittest
+  call assert_notequal(l:current, bufnr())
+
+  call delete("first.unittest")
+  call delete("winfix.unittest")
+  call delete("last.unittest")
+endfunc
+
+" Don't allow global marks to change the current 'winfixbuf' window
+func Test_marks_mappings_fail()
+  call s:reset_all_buffers()
+
+  let l:other = s:make_buffer_pairs()
+  let l:current = bufnr()
+  execute "buffer! " . l:other
+  normal mA
+  execute "buffer! " . l:current
+  normal mB
+
+  call assert_fails("normal `A", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  call assert_fails("normal 'A", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  set nowinfixbuf
+
+  normal `A
+  call assert_equal(l:other, bufnr())
+endfunc
+
+" Allow global marks in a 'winfixbuf' window if the jump is the same buffer
+func Test_marks_mappings_pass_intra_move()
+  call s:reset_all_buffers()
+
+  let l:current = bufnr()
+  call append(0, ["some line", "another line"])
+  normal mA
+  normal j
+  normal mB
+
+  set winfixbuf
+
+  normal `A
+  call assert_equal(l:current, bufnr())
+endfunc
+
+" Fail :next but :next! is allowed
+func Test_next()
+  call s:reset_all_buffers()
+
+  let [l:first, _] = s:make_args_list()
+  first!
+
+  call assert_fails("next", "E1513:")
+  call assert_equal(l:first, bufnr())
+
+  next!
+  call assert_notequal(l:first, bufnr())
+endfunc
+
+" Ensure :mksession saves 'winfixbuf' details
+func Test_mksession()
+  CheckFeature mksession
+  call s:reset_all_buffers()
+
+  set sessionoptions+=options
+  set winfixbuf
+
+  mksession test_winfixbuf_Test_mksession.vim
+
+  call s:reset_all_buffers()
+  let l:winfixbuf = &winfixbuf
+  call assert_equal(0, l:winfixbuf)
+
+  source test_winfixbuf_Test_mksession.vim
+
+  let l:winfixbuf = &winfixbuf
+  call assert_equal(1, l:winfixbuf)
+
+  set sessionoptions&
+  call delete("test_winfixbuf_Test_mksession.vim")
+endfunc
+
+" Allow :next if the next index is the same as the current buffer
+func Test_next_same_buffer()
+  call s:reset_all_buffers()
+
+  enew
+  file foo
+  enew
+  file bar
+  enew
+  file fizz
+  enew
+  file buzz
+  args foo foo bar fizz buzz
+
+  edit foo
+  set winfixbuf
+  let l:current = bufnr()
+
+  " Allow :next because the args list is `[foo] foo bar fizz buzz
+  next
+  call assert_equal(l:current, bufnr())
+
+  " Fail :next because the args list is `foo [foo] bar fizz buzz
+  " and the next buffer would be bar, which is a different buffer
+  call assert_fails("next", "E1513:")
+  call assert_equal(l:current, bufnr())
+endfunc
+
+" Fail to jump to a tag with g<C-]> if 'winfixbuf' is enabled
+func Test_normal_g_ctrl_square_bracket_right()
+  call s:reset_all_buffers()
+
+  set tags=Xtags
+  call writefile(["!_TAG_FILE_ENCODING\tutf-8\t//",
+        \ "one\tXfile\t1",
+        \ "three\tXfile\t3",
+        \ "two\tXfile\t2"],
+        \ "Xtags")
+  call writefile(["one", "two", "three"], "Xfile")
+  call writefile(["one"], "Xother")
+  edit Xother
+
+  set winfixbuf
+
+  let l:current = bufnr()
+
+  call assert_fails("normal g\<C-]>", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  set tags&
+  call delete("Xtags")
+  call delete("Xfile")
+  call delete("Xother")
+endfunc
+
+" Fail to jump to a tag with g<RightMouse> if 'winfixbuf' is enabled
+func Test_normal_g_rightmouse()
+  call s:reset_all_buffers()
+  set mouse=n
+
+  set tags=Xtags
+  call writefile(["!_TAG_FILE_ENCODING\tutf-8\t//",
+        \ "one\tXfile\t1",
+        \ "three\tXfile\t3",
+        \ "two\tXfile\t2"],
+        \ "Xtags")
+  call writefile(["one", "two", "three"], "Xfile")
+  call writefile(["one"], "Xother")
+  edit Xother
+  execute "normal \<C-]>"
+
+  set winfixbuf
+
+  let l:current = bufnr()
+
+  call assert_fails("normal g\<RightMouse>", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  set tags&
+  set mouse&
+  call delete("Xtags")
+  call delete("Xfile")
+  call delete("Xother")
+endfunc
+
+" Fail to jump to a tag with g] if 'winfixbuf' is enabled
+func Test_normal_g_square_bracket_right()
+  call s:reset_all_buffers()
+
+  set tags=Xtags
+  call writefile(["!_TAG_FILE_ENCODING\tutf-8\t//",
+        \ "one\tXfile\t1",
+        \ "three\tXfile\t3",
+        \ "two\tXfile\t2"],
+        \ "Xtags")
+  call writefile(["one", "two", "three"], "Xfile")
+  call writefile(["one"], "Xother")
+  edit Xother
+
+  set winfixbuf
+
+  let l:current = bufnr()
+
+  call assert_fails("normal g]", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  set tags&
+  call delete("Xtags")
+  call delete("Xfile")
+  call delete("Xother")
+endfunc
+
+" Fail to jump to a tag with <C-RightMouse> if 'winfixbuf' is enabled
+func Test_normal_ctrl_rightmouse()
+  call s:reset_all_buffers()
+  set mouse=n
+
+  set tags=Xtags
+  call writefile(["!_TAG_FILE_ENCODING\tutf-8\t//",
+        \ "one\tXfile\t1",
+        \ "three\tXfile\t3",
+        \ "two\tXfile\t2"],
+        \ "Xtags")
+  call writefile(["one", "two", "three"], "Xfile")
+  call writefile(["one"], "Xother")
+  edit Xother
+  execute "normal \<C-]>"
+
+  set winfixbuf
+
+  let l:current = bufnr()
+
+  call assert_fails("normal \<C-RightMouse>", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  set tags&
+  set mouse&
+  call delete("Xtags")
+  call delete("Xfile")
+  call delete("Xother")
+endfunc
+
+" Fail to jump to a tag with <C-t> if 'winfixbuf' is enabled
+func Test_normal_ctrl_t()
+  call s:reset_all_buffers()
+
+  set tags=Xtags
+  call writefile(["!_TAG_FILE_ENCODING\tutf-8\t//",
+        \ "one\tXfile\t1",
+        \ "three\tXfile\t3",
+        \ "two\tXfile\t2"],
+        \ "Xtags")
+  call writefile(["one", "two", "three"], "Xfile")
+  call writefile(["one"], "Xother")
+  edit Xother
+  execute "normal \<C-]>"
+
+  set winfixbuf
+
+  let l:current = bufnr()
+
+  call assert_fails("normal \<C-t>", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  set tags&
+  call delete("Xtags")
+  call delete("Xfile")
+  call delete("Xother")
+endfunc
+
+" Disallow <C-^> in 'winfixbuf' windows
+func Test_normal_ctrl_hat()
+  call s:reset_all_buffers()
+  clearjumps
+
+  enew
+  file first
+  let l:first = bufnr()
+
+  enew
+  file current
+  let l:current = bufnr()
+
+  set winfixbuf
+
+  call assert_fails("normal \<C-^>", "E1513:")
+  call assert_equal(l:current, bufnr())
+endfunc
+
+" Allow <C-i> in 'winfixbuf' windows if the movement stays within the buffer
+func Test_normal_ctrl_i_pass()
+  call s:reset_all_buffers()
+  clearjumps
+
+  enew
+  file first
+  let l:first = bufnr()
+
+  enew!
+  file current
+  let l:current = bufnr()
+  " Add some lines so we can populate a jumplist"
+  call append(0, ["some line", "another line"])
+  " Add an entry to the jump list
+  " Go up another line
+  normal m`
+  normal k
+  execute "normal \<C-o>"
+
+  set winfixbuf
+
+  let l:line = getcurpos()[1]
+  execute "normal 1\<C-i>"
+  call assert_notequal(l:line, getcurpos()[1])
+endfunc
+
+" Disallow <C-o> in 'winfixbuf' windows if it would cause the buffer to switch
+func Test_normal_ctrl_o_fail()
+  call s:reset_all_buffers()
+  clearjumps
+
+  enew
+  file first
+  let l:first = bufnr()
+
+  enew
+  file current
+  let l:current = bufnr()
+
+  set winfixbuf
+
+  call assert_fails("normal \<C-o>", "E1513:")
+  call assert_equal(l:current, bufnr())
+endfunc
+
+" Allow <C-o> in 'winfixbuf' windows if the movement stays within the buffer
+func Test_normal_ctrl_o_pass()
+  call s:reset_all_buffers()
+  clearjumps
+
+  enew
+  file first
+  let l:first = bufnr()
+
+  enew!
+  file current
+  let l:current = bufnr()
+  " Add some lines so we can populate a jumplist
+  call append(0, ["some line", "another line"])
+  " Add an entry to the jump list
+  " Go up another line
+  normal m`
+  normal k
+
+  set winfixbuf
+
+  execute "normal \<C-o>"
+  call assert_equal(l:current, bufnr())
+endfunc
+
+" Fail to jump to a tag with <C-]> if 'winfixbuf' is enabled
+func Test_normal_ctrl_square_bracket_right()
+  call s:reset_all_buffers()
+
+  set tags=Xtags
+  call writefile(["!_TAG_FILE_ENCODING\tutf-8\t//",
+        \ "one\tXfile\t1",
+        \ "three\tXfile\t3",
+        \ "two\tXfile\t2"],
+        \ "Xtags")
+  call writefile(["one", "two", "three"], "Xfile")
+  call writefile(["one"], "Xother")
+  edit Xother
+
+  set winfixbuf
+
+  let l:current = bufnr()
+
+  call assert_fails("normal \<C-]>", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  set tags&
+  call delete("Xtags")
+  call delete("Xfile")
+  call delete("Xother")
+endfunc
+
+" Allow <C-w><C-]> with 'winfixbuf' enabled because it runs in a new, split window
+func Test_normal_ctrl_w_ctrl_square_bracket_right()
+  call s:reset_all_buffers()
+
+  set tags=Xtags
+  call writefile(["!_TAG_FILE_ENCODING\tutf-8\t//",
+        \ "one\tXfile\t1",
+        \ "three\tXfile\t3",
+        \ "two\tXfile\t2"],
+        \ "Xtags")
+  call writefile(["one", "two", "three"], "Xfile")
+  call writefile(["one"], "Xother")
+  edit Xother
+
+  set winfixbuf
+
+  let l:current_windows = s:get_windows_count()
+  execute "normal \<C-w>\<C-]>"
+  call assert_equal(l:current_windows + 1, s:get_windows_count())
+
+  set tags&
+  call delete("Xtags")
+  call delete("Xfile")
+  call delete("Xother")
+endfunc
+
+" Allow <C-w>g<C-]> with 'winfixbuf' enabled because it runs in a new, split window
+func Test_normal_ctrl_w_g_ctrl_square_bracket_right()
+  call s:reset_all_buffers()
+
+  set tags=Xtags
+  call writefile(["!_TAG_FILE_ENCODING\tutf-8\t//",
+        \ "one\tXfile\t1",
+        \ "three\tXfile\t3",
+        \ "two\tXfile\t2"],
+        \ "Xtags")
+  call writefile(["one", "two", "three"], "Xfile")
+  call writefile(["one"], "Xother")
+  edit Xother
+
+  set winfixbuf
+
+  let l:current_windows = s:get_windows_count()
+  execute "normal \<C-w>g\<C-]>"
+  call assert_equal(l:current_windows + 1, s:get_windows_count())
+
+  set tags&
+  call delete("Xtags")
+  call delete("Xfile")
+  call delete("Xother")
+endfunc
+
+" Fail to jump to a tag with <C-]> if 'winfixbuf' is enabled
+func Test_normal_gt()
+  call s:reset_all_buffers()
+
+  set tags=Xtags
+  call writefile(["!_TAG_FILE_ENCODING\tutf-8\t//",
+        \ "one\tXfile\t1",
+        \ "three\tXfile\t3",
+        \ "two\tXfile\t2"],
+        \ "Xtags")
+  call writefile(["one", "two", "three"], "Xfile")
+  call writefile(["one", "two", "three"], "Xother")
+  edit Xother
+
+  set winfixbuf
+
+  let l:current = bufnr()
+
+  call assert_fails("normal \<C-]>", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  set tags&
+  call delete("Xtags")
+  call delete("Xfile")
+  call delete("Xother")
+endfunc
+
+" Prevent gF from switching a 'winfixbuf' window's buffer
+func Test_normal_gF()
+  call s:reset_all_buffers()
+
+  let l:file = tempname()
+  call append(0, [l:file])
+  call writefile([], l:file)
+  " Place the cursor onto the line that has `l:file`
+  normal gg
+  " Prevent Vim from erroring with "No write since last change @ command
+  " line" when we try to call gF, later.
+  set hidden
+
+  set winfixbuf
+
+  let l:buffer = bufnr()
+
+  call assert_fails("normal gF", "E1513:")
+  call assert_equal(l:buffer, bufnr())
+
+  set nowinfixbuf
+
+  normal gF
+  call assert_notequal(l:buffer, bufnr())
+
+  call delete(l:file)
+endfunc
+
+" Prevent gf from switching a 'winfixbuf' window's buffer
+func Test_normal_gf()
+  call s:reset_all_buffers()
+
+  let l:file = tempname()
+  call append(0, [l:file])
+  call writefile([], l:file)
+  " Place the cursor onto the line that has `l:file`
+  normal gg
+  " Prevent Vim from erroring with "No write since last change @ command
+  " line" when we try to call gf, later.
+  set hidden
+
+  set winfixbuf
+
+  let l:buffer = bufnr()
+
+  call assert_fails("normal gf", "E1513:")
+  call assert_equal(l:buffer, bufnr())
+
+  set nowinfixbuf
+
+  normal gf
+  call assert_notequal(l:buffer, bufnr())
+
+  call delete(l:file)
+endfunc
+
+" Fail "goto file under the cursor" (using [f, which is the same as `:normal gf`)
+func Test_normal_square_bracket_left_f()
+  call s:reset_all_buffers()
+
+  let l:file = tempname()
+  call append(0, [l:file])
+  call writefile([], l:file)
+  " Place the cursor onto the line that has `l:file`
+  normal gg
+  " Prevent Vim from erroring with "No write since last change @ command
+  " line" when we try to call gf, later.
+  set hidden
+
+  set winfixbuf
+
+  let l:buffer = bufnr()
+
+  call assert_fails("normal [f", "E1513:")
+  call assert_equal(l:buffer, bufnr())
+
+  set nowinfixbuf
+
+  normal [f
+  call assert_notequal(l:buffer, bufnr())
+
+  call delete(l:file)
+endfunc
+
+" Fail to go to a C macro with [<C-d> if 'winfixbuf' is enabled
+func Test_normal_square_bracket_left_ctrl_d()
+  call s:reset_all_buffers()
+
+  let l:include_file = tempname() . ".h"
+  call writefile(["min(1, 12);",
+        \ '#include "' . l:include_file . '"'
+        \ ],
+        \ "main.c")
+  call writefile(["#define min(X, Y)  ((X) < (Y) ? (X) : (Y))"], l:include_file)
+  edit main.c
+  normal ]\<C-d>
+
+  set winfixbuf
+
+  let l:current = bufnr()
+
+  call assert_fails("normal [\<C-d>", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  set nowinfixbuf
+
+  execute "normal [\<C-d>"
+  call assert_notequal(l:current, bufnr())
+
+  call delete("main.c")
+  call delete(l:include_file)
+endfunc
+
+" Fail to go to a C macro with ]<C-d> if 'winfixbuf' is enabled
+func Test_normal_square_bracket_right_ctrl_d()
+  call s:reset_all_buffers()
+
+  let l:include_file = tempname() . ".h"
+  call writefile(["min(1, 12);",
+        \ '#include "' . l:include_file . '"'
+        \ ],
+        \ "main.c")
+  call writefile(["#define min(X, Y)  ((X) < (Y) ? (X) : (Y))"], l:include_file)
+  edit main.c
+
+  set winfixbuf
+
+  let l:current = bufnr()
+
+  call assert_fails("normal ]\<C-d>", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  set nowinfixbuf
+
+  execute "normal ]\<C-d>"
+  call assert_notequal(l:current, bufnr())
+
+  call delete("main.c")
+  call delete(l:include_file)
+endfunc
+
+" Fail to go to a C macro with [<C-i> if 'winfixbuf' is enabled
+func Test_normal_square_bracket_left_ctrl_i()
+  call s:reset_all_buffers()
+
+  let l:include_file = tempname() . ".h"
+  call writefile(['#include "' . l:include_file . '"',
+        \ "min(1, 12);",
+        \ ],
+        \ "main.c")
+  call writefile(["#define min(X, Y)  ((X) < (Y) ? (X) : (Y))"], l:include_file)
+  edit main.c
+  " Move to the line with `min(1, 12);` on it"
+  normal j
+
+  set define=^\\s*#\\s*define
+  set include=^\\s*#\\s*include
+  set path=.,/usr/include,,
+
+  let l:current = bufnr()
+
+  set winfixbuf
+
+  call assert_fails("normal [\<C-i>", "E1513:")
+
+  set nowinfixbuf
+
+  execute "normal [\<C-i>"
+  call assert_notequal(l:current, bufnr())
+
+  set define&
+  set include&
+  set path&
+  call delete("main.c")
+  call delete(l:include_file)
+endfunc
+
+" Fail to go to a C macro with ]<C-i> if 'winfixbuf' is enabled
+func Test_normal_square_bracket_right_ctrl_i()
+  call s:reset_all_buffers()
+
+  let l:include_file = tempname() . ".h"
+  call writefile(["min(1, 12);",
+        \ '#include "' . l:include_file . '"'
+        \ ],
+        \ "main.c")
+  call writefile(["#define min(X, Y)  ((X) < (Y) ? (X) : (Y))"], l:include_file)
+  edit main.c
+
+  set winfixbuf
+
+  set define=^\\s*#\\s*define
+  set include=^\\s*#\\s*include
+  set path=.,/usr/include,,
+
+  let l:current = bufnr()
+
+  call assert_fails("normal ]\<C-i>", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  set nowinfixbuf
+
+  execute "normal ]\<C-i>"
+  call assert_notequal(l:current, bufnr())
+
+  set define&
+  set include&
+  set path&
+  call delete("main.c")
+  call delete(l:include_file)
+endfunc
+
+" Fail "goto file under the cursor" (using ]f, which is the same as `:normal gf`)
+func Test_normal_square_bracket_right_f()
+  call s:reset_all_buffers()
+
+  let l:file = tempname()
+  call append(0, [l:file])
+  call writefile([], l:file)
+  " Place the cursor onto the line that has `l:file`
+  normal gg
+  " Prevent Vim from erroring with "No write since last change @ command
+  " line" when we try to call gf, later.
+  set hidden
+
+  set winfixbuf
+
+  let l:buffer = bufnr()
+
+  call assert_fails("normal ]f", "E1513:")
+  call assert_equal(l:buffer, bufnr())
+
+  set nowinfixbuf
+
+  normal ]f
+  call assert_notequal(l:buffer, bufnr())
+
+  call delete(l:file)
+endfunc
+
+" Fail to jump to a tag with v<C-]> if 'winfixbuf' is enabled
+func Test_normal_v_ctrl_square_bracket_right()
+  call s:reset_all_buffers()
+
+  set tags=Xtags
+  call writefile(["!_TAG_FILE_ENCODING\tutf-8\t//",
+        \ "one\tXfile\t1",
+        \ "three\tXfile\t3",
+        \ "two\tXfile\t2"],
+        \ "Xtags")
+  call writefile(["one", "two", "three"], "Xfile")
+  call writefile(["one"], "Xother")
+  edit Xother
+
+  set winfixbuf
+
+  let l:current = bufnr()
+
+  call assert_fails("normal v\<C-]>", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  set tags&
+  call delete("Xtags")
+  call delete("Xfile")
+  call delete("Xother")
+endfunc
+
+" Fail to jump to a tag with vg<C-]> if 'winfixbuf' is enabled
+func Test_normal_v_g_ctrl_square_bracket_right()
+  call s:reset_all_buffers()
+
+  set tags=Xtags
+  call writefile(["!_TAG_FILE_ENCODING\tutf-8\t//",
+        \ "one\tXfile\t1",
+        \ "three\tXfile\t3",
+        \ "two\tXfile\t2"],
+        \ "Xtags")
+  call writefile(["one", "two", "three"], "Xfile")
+  call writefile(["one"], "Xother")
+  edit Xother
+
+  set winfixbuf
+
+  let l:current = bufnr()
+
+  call assert_fails("normal vg\<C-]>", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  set tags&
+  call delete("Xtags")
+  call delete("Xfile")
+  call delete("Xother")
+endfunc
+
+" Allow :pedit because, unlike :edit, it uses a separate window
+func Test_pedit()
+  call s:reset_all_buffers()
+
+  let l:other = s:make_buffer_pairs()
+
+  pedit other
+
+  execute "normal \<C-w>w"
+  call assert_equal(l:other, bufnr())
+endfunc
+
+" Fail :pop but :pop! is allowed
+func Test_pop()
+  call s:reset_all_buffers()
+
+  set tags=Xtags
+  call writefile(["!_TAG_FILE_ENCODING\tutf-8\t//",
+        \ "thesame\tXfile\t1;\"\td\tfile:",
+        \ "thesame\tXfile\t2;\"\td\tfile:",
+        \ "thesame\tXfile\t3;\"\td\tfile:",
+        \ ],
+        \ "Xtags")
+  call writefile(["thesame one", "thesame two", "thesame three"], "Xfile")
+  call writefile(["thesame one"], "Xother")
+  edit Xother
+
+  tag thesame
+
+  set winfixbuf
+
+  let l:current = bufnr()
+
+  call assert_fails("pop", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  pop!
+  call assert_notequal(l:current, bufnr())
+
+  set tags&
+  call delete("Xtags")
+  call delete("Xfile")
+  call delete("Xother")
+endfunc
+
+" Fail :previous but :previous! is allowed
+func Test_previous()
+  call s:reset_all_buffers()
+
+  let [l:first, _] = s:make_args_list()
+  next!
+
+  call assert_fails("previous", "E1513:")
+  call assert_notequal(l:first, bufnr())
+
+  previous!
+  call assert_equal(l:first, bufnr())
+endfunc
+
+" Fail pydo if it changes a window with 'winfixbuf' is set
+func Test_python_pydo()
+  CheckFeature pythonx
+  call s:reset_all_buffers()
+
+  enew
+  file first
+  let g:_previous_buffer = bufnr()
+
+  enew
+  file second
+
+  set winfixbuf
+
+  python << EOF
+import vim
+
+def test_winfixbuf_Test_python_pydo_set_buffer():
+    buffer = vim.vars['_previous_buffer']
+    vim.current.buffer = vim.buffers[buffer]
+EOF
+
+  try
+    pydo test_winfixbuf_Test_python_pydo_set_buffer()
+  catch /pynvim\.api\.common\.NvimError: E1513: Cannot edit buffer\. 'winfixbuf' is enabled/
+    let l:caught = 1
+  endtry
+
+  call assert_equal(1, l:caught)
+
+  unlet g:_previous_buffer
+endfunc
+
+" Fail pyfile if it changes a window with 'winfixbuf' is set
+func Test_python_pyfile()
+  CheckFeature pythonx
+  call s:reset_all_buffers()
+
+  enew
+  file first
+  let g:_previous_buffer = bufnr()
+
+  enew
+  file second
+
+  set winfixbuf
+
+  call writefile(["import vim",
+        \ "buffer = vim.vars['_previous_buffer']",
+        \ "vim.current.buffer = vim.buffers[buffer]",
+        \ ],
+        \ "file.py")
+
+  try
+    pyfile file.py
+  catch /pynvim\.api\.common\.NvimError: E1513: Cannot edit buffer\. 'winfixbuf' is enabled/
+    let l:caught = 1
+  endtry
+
+  call assert_equal(1, l:caught)
+
+  call delete("file.py")
+  unlet g:_previous_buffer
+endfunc
+
+" Fail vim.current.buffer if 'winfixbuf' is set
+func Test_python_vim_current_buffer()
+  CheckFeature pythonx
+  call s:reset_all_buffers()
+
+  enew
+  file first
+  let g:_previous_buffer = bufnr()
+
+  enew
+  file second
+
+  let l:caught = 0
+
+  set winfixbuf
+
+  try
+    python << EOF
+import vim
+
+buffer = vim.vars["_previous_buffer"]
+vim.current.buffer = vim.buffers[buffer]
+EOF
+  catch /pynvim\.api\.common\.NvimError: E1513: Cannot edit buffer\. 'winfixbuf' is enabled/
+    let l:caught = 1
+  endtry
+
+  call assert_equal(1, l:caught)
+  unlet g:_previous_buffer
+endfunc
+
+" Ensure remapping to a disabled action still triggers failures
+func Test_remap_key_fail()
+  call s:reset_all_buffers()
+
+  enew
+  file first
+  let l:first = bufnr()
+
+  enew
+  file current
+  let l:current = bufnr()
+
+  set winfixbuf
+
+  nnoremap g <C-^>
+
+  call assert_fails("normal g", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  nunmap g
+endfunc
+
+" Ensure remapping a disabled key to something valid does trigger any failures
+func Test_remap_key_pass()
+  call s:reset_all_buffers()
+
+  enew
+  file first
+  let l:first = bufnr()
+
+  enew
+  file current
+  let l:current = bufnr()
+
+  set winfixbuf
+
+  call assert_fails("normal \<C-^>", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  " Disallow <C-^> by default but allow it if the command does something else
+  nnoremap <C-^> :echo "hello!"
+
+  execute "normal \<C-^>"
+  call assert_equal(l:current, bufnr())
+
+  nunmap <C-^>
+endfunc
+
+" Fail :rewind but :rewind! is allowed
+func Test_rewind()
+  call s:reset_all_buffers()
+
+  let [l:first, _] = s:make_args_list()
+  next!
+
+  call assert_fails("rewind", "E1513:")
+  call assert_notequal(l:first, bufnr())
+
+  rewind!
+  call assert_equal(l:first, bufnr())
+endfunc
+
+" Allow :sblast because it opens the buffer in a new, split window
+func Test_sblast()
+  call s:reset_all_buffers()
+
+  let l:other = s:make_buffer_pairs(1)
+  bfirst!
+  let l:current = bufnr()
+
+  sblast
+  call assert_equal(l:other, bufnr())
+endfunc
+
+" Fail :sbprevious but :sbprevious! is allowed
+func Test_sbprevious()
+  call s:reset_all_buffers()
+
+  let l:other = s:make_buffer_pairs()
+  let l:current = bufnr()
+
+  sbprevious
+  call assert_equal(l:other, bufnr())
+endfunc
+
+" Make sure 'winfixbuf' can be set using 'winfixbuf' or 'wfb'
+func Test_short_option()
+  call s:reset_all_buffers()
+
+  call s:make_buffer_pairs()
+
+  set winfixbuf
+  call assert_fails("edit something_else", "E1513")
+
+  set nowinfixbuf
+  set wfb
+  call assert_fails("edit another_place", "E1513")
+
+  set nowfb
+  edit last_place
+endfunc
+
+" Allow :snext because it makes a new window
+func Test_snext()
+  call s:reset_all_buffers()
+
+  let [l:first, _] = s:make_args_list()
+  first!
+
+  let l:current_window = win_getid()
+
+  snext
+  call assert_notequal(l:current_window, win_getid())
+  call assert_notequal(l:first, bufnr())
+endfunc
+
+" Ensure the first has 'winfixbuf' and a new split window is 'nowinfixbuf'
+func Test_split_window()
+  call s:reset_all_buffers()
+
+  split
+  execute "normal \<C-w>j"
+
+  set winfixbuf
+
+  let l:winfix_window_1 = win_getid()
+  vsplit
+  let l:winfix_window_2 = win_getid()
+
+  call assert_equal(1, getwinvar(l:winfix_window_1, "&winfixbuf"))
+  call assert_equal(0, getwinvar(l:winfix_window_2, "&winfixbuf"))
+endfunc
+
+" Fail :tNext but :tNext! is allowed
+func Test_tNext()
+  call s:reset_all_buffers()
+
+  set tags=Xtags
+  call writefile(["!_TAG_FILE_ENCODING\tutf-8\t//",
+        \ "thesame\tXfile\t1;\"\td\tfile:",
+        \ "thesame\tXfile\t2;\"\td\tfile:",
+        \ "thesame\tXfile\t3;\"\td\tfile:",
+        \ ],
+        \ "Xtags")
+  call writefile(["thesame one", "thesame two", "thesame three"], "Xfile")
+  call writefile(["thesame one"], "Xother")
+  edit Xother
+
+  tag thesame
+  execute "normal \<C-^>"
+  tnext!
+
+  set winfixbuf
+
+  let l:current = bufnr()
+
+  call assert_fails("tNext", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  tNext!
+
+  set tags&
+  call delete("Xtags")
+  call delete("Xfile")
+  call delete("Xother")
+endfunc
+
+" Call :tabdo and choose the next available 'nowinfixbuf' window.
+func Test_tabdo_choose_available_window()
+  call s:reset_all_buffers()
+
+  let [l:first, _] = s:make_args_list()
+
+  " Make a split window that is 'nowinfixbuf' but make it the second-to-last
+  " window so that :tabdo will first try the 'winfixbuf' window, pass over it,
+  " and prefer the other 'nowinfixbuf' window, instead.
+  "
+  " +-------------------+
+  " |   'nowinfixbuf'   |
+  " +-------------------+
+  " |    'winfixbuf'    |  <-- Cursor is here
+  " +-------------------+
+  split
+  let l:nowinfixbuf_window = win_getid()
+  " Move to the 'winfixbuf' window now
+  execute "normal \<C-w>j"
+  let l:winfixbuf_window = win_getid()
+
+  let l:expected_windows = s:get_windows_count()
+  tabdo echo ''
+  call assert_equal(l:nowinfixbuf_window, win_getid())
+  call assert_equal(l:first, bufnr())
+  call assert_equal(l:expected_windows, s:get_windows_count())
+endfunc
+
+" Call :tabdo and create a new split window if all available windows are 'winfixbuf'.
+func Test_tabdo_make_new_window()
+  call s:reset_all_buffers()
+
+  let [l:first, _] = s:make_buffers_list()
+  execute "buffer! " . l:first
+
+  let l:current = win_getid()
+  let l:current_windows = s:get_windows_count()
+
+  tabdo echo ''
+  call assert_notequal(l:current, win_getid())
+  call assert_equal(l:first, bufnr())
+  execute "normal \<C-w>j"
+  call assert_equal(l:first, bufnr())
+  call assert_equal(l:current_windows + 1, s:get_windows_count())
+endfunc
+
+" Fail :tag but :tag! is allowed
+func Test_tag()
+  call s:reset_all_buffers()
+
+  set tags=Xtags
+  call writefile(["!_TAG_FILE_ENCODING\tutf-8\t//",
+        \ "one\tXfile\t1",
+        \ "three\tXfile\t3",
+        \ "two\tXfile\t2"],
+        \ "Xtags")
+  call writefile(["one", "two", "three"], "Xfile")
+  call writefile(["one"], "Xother")
+  edit Xother
+
+  set winfixbuf
+
+  let l:current = bufnr()
+
+  call assert_fails("tag one", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  tag! one
+  call assert_notequal(l:current, bufnr())
+
+  set tags&
+  call delete("Xtags")
+  call delete("Xfile")
+  call delete("Xother")
+endfunc
+
+
+" Fail :tfirst but :tfirst! is allowed
+func Test_tfirst()
+  call s:reset_all_buffers()
+
+  set tags=Xtags
+  call writefile(["!_TAG_FILE_ENCODING\tutf-8\t//",
+        \ "one\tXfile\t1",
+        \ "three\tXfile\t3",
+        \ "two\tXfile\t2"],
+        \ "Xtags")
+  call writefile(["one", "two", "three"], "Xfile")
+  call writefile(["one"], "Xother")
+  edit Xother
+
+  set winfixbuf
+
+  let l:current = bufnr()
+
+  call assert_fails("tfirst", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  tfirst!
+  call assert_notequal(l:current, bufnr())
+
+  set tags&
+  call delete("Xtags")
+  call delete("Xfile")
+  call delete("Xother")
+endfunc
+
+" Fail :tjump but :tjump! is allowed
+func Test_tjump()
+  call s:reset_all_buffers()
+
+  set tags=Xtags
+  call writefile(["!_TAG_FILE_ENCODING\tutf-8\t//",
+        \ "one\tXfile\t1",
+        \ "three\tXfile\t3",
+        \ "two\tXfile\t2"],
+        \ "Xtags")
+  call writefile(["one", "two", "three"], "Xfile")
+  call writefile(["one"], "Xother")
+  edit Xother
+
+  set winfixbuf
+
+  let l:current = bufnr()
+
+  call assert_fails("tjump one", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  tjump! one
+  call assert_notequal(l:current, bufnr())
+
+  set tags&
+  call delete("Xtags")
+  call delete("Xfile")
+  call delete("Xother")
+endfunc
+
+" Fail :tlast but :tlast! is allowed
+func Test_tlast()
+  call s:reset_all_buffers()
+
+  set tags=Xtags
+  call writefile(["!_TAG_FILE_ENCODING\tutf-8\t//",
+        \ "one\tXfile\t1",
+        \ "three\tXfile\t3",
+        \ "two\tXfile\t2"],
+        \ "Xtags")
+  call writefile(["one", "two", "three"], "Xfile")
+  edit Xfile
+  tjump one
+  edit Xfile
+
+  set winfixbuf
+
+  let l:current = bufnr()
+
+  call assert_fails("tlast", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  tlast!
+  call assert_equal(l:current, bufnr())
+
+  set tags&
+  call delete("Xtags")
+  call delete("Xfile")
+endfunc
+
+" Fail :tnext but :tnext! is allowed
+func Test_tnext()
+  call s:reset_all_buffers()
+
+  set tags=Xtags
+  call writefile(["!_TAG_FILE_ENCODING\tutf-8\t//",
+        \ "thesame\tXfile\t1;\"\td\tfile:",
+        \ "thesame\tXfile\t2;\"\td\tfile:",
+        \ "thesame\tXfile\t3;\"\td\tfile:",
+        \ ],
+        \ "Xtags")
+  call writefile(["thesame one", "thesame two", "thesame three"], "Xfile")
+  call writefile(["thesame one"], "Xother")
+  edit Xother
+
+  tag thesame
+  execute "normal \<C-^>"
+
+  set winfixbuf
+
+  let l:current = bufnr()
+
+  call assert_fails("tnext", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  tnext!
+  call assert_notequal(l:current, bufnr())
+
+  set tags&
+  call delete("Xtags")
+  call delete("Xfile")
+  call delete("Xother")
+endfunc
+
+" Fail :tprevious but :tprevious! is allowed
+func Test_tprevious()
+  call s:reset_all_buffers()
+
+  set tags=Xtags
+  call writefile(["!_TAG_FILE_ENCODING\tutf-8\t//",
+        \ "thesame\tXfile\t1;\"\td\tfile:",
+        \ "thesame\tXfile\t2;\"\td\tfile:",
+        \ "thesame\tXfile\t3;\"\td\tfile:",
+        \ ],
+        \ "Xtags")
+  call writefile(["thesame one", "thesame two", "thesame three"], "Xfile")
+  call writefile(["thesame one"], "Xother")
+  edit Xother
+
+  tag thesame
+  execute "normal \<C-^>"
+  tnext!
+
+  set winfixbuf
+
+  let l:current = bufnr()
+
+  call assert_fails("tprevious", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  tprevious!
+
+  set tags&
+  call delete("Xtags")
+  call delete("Xfile")
+  call delete("Xother")
+endfunc
+
+" Fail :view but :view! is allowed
+func Test_view()
+  call s:reset_all_buffers()
+
+  let l:other = s:make_buffer_pairs()
+  let l:current = bufnr()
+
+  call assert_fails("view other", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  view! other
+  call assert_equal(l:other, bufnr())
+endfunc
+
+" Fail :visual but :visual! is allowed
+func Test_visual()
+  call s:reset_all_buffers()
+
+  let l:other = s:make_buffer_pairs()
+  let l:current = bufnr()
+
+  call assert_fails("visual other", "E1513:")
+  call assert_equal(l:current, bufnr())
+
+  visual! other
+  call assert_equal(l:other, bufnr())
+endfunc
+
+" Fail :vimgrep but :vimgrep! is allowed
+func Test_vimgrep()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  edit first.unittest
+  call append(0, ["some-search-term"])
+  write
+
+  edit winfix.unittest
+  call append(0, ["some-search-term"])
+  write
+  let l:current = bufnr()
+
+  set winfixbuf
+
+  edit! last.unittest
+  call append(0, ["some-search-term"])
+  write
+  let l:last = bufnr()
+
+  buffer! winfix.unittest
+
+  call assert_fails("vimgrep /some-search-term/ *.unittest")
+  call assert_equal(l:current, bufnr())
+
+  " Don't error and also do swap to the first match because ! was included
+  vimgrep! /some-search-term/ *.unittest
+  call assert_notequal(l:current, bufnr())
+
+  call delete("first.unittest")
+  call delete("winfix.unittest")
+  call delete("last.unittest")
+endfunc
+
+" Fail :vimgrepadd but ::vimgrepadd! is allowed
+func Test_vimgrepadd()
+  CheckFeature quickfix
+  call s:reset_all_buffers()
+
+  edit first.unittest
+  call append(0, ["some-search-term"])
+  write
+
+  edit winfix.unittest
+  call append(0, ["some-search-term"])
+  write
+  let l:current = bufnr()
+
+  set winfixbuf
+
+  edit! last.unittest
+  call append(0, ["some-search-term"])
+  write
+  let l:last = bufnr()
+
+  buffer! winfix.unittest
+
+  call assert_fails("vimgrepadd /some-search-term/ *.unittest")
+  call assert_equal(l:current, bufnr())
+
+  vimgrepadd! /some-search-term/ *.unittest
+  call assert_notequal(l:current, bufnr())
+  call delete("first.unittest")
+  call delete("winfix.unittest")
+  call delete("last.unittest")
+endfunc
+
+" Fail :wNext but :wNext! is allowed
+func Test_wNext()
+  call s:reset_all_buffers()
+
+  let [l:first, _] = s:make_args_list()
+  next!
+
+  call assert_fails("wNext", "E1513:")
+  call assert_notequal(l:first, bufnr())
+
+  wNext!
+  call assert_equal(l:first, bufnr())
+
+  call delete("first")
+  call delete("middle")
+  call delete("last")
+endfunc
+
+" Allow :windo unless `:windo foo` would change a 'winfixbuf' window's buffer
+func Test_windo()
+  call s:reset_all_buffers()
+
+  let l:current_window = win_getid()
+  let l:current_buffer = bufnr()
+  split
+  enew
+  file some_other_buffer
+
+  set winfixbuf
+
+  let l:current = win_getid()
+
+  windo echo ''
+  call assert_equal(l:current_window, win_getid())
+
+  call assert_fails('execute "windo buffer ' . l:current_buffer . '"', "E1513:")
+  call assert_equal(l:current_window, win_getid())
+
+  execute "windo buffer! " . l:current_buffer
+  call assert_equal(l:current_window, win_getid())
+endfunc
+
+" Fail :wnext but :wnext! is allowed
+func Test_wnext()
+  call s:reset_all_buffers()
+
+  let [_, l:last] = s:make_args_list()
+  next!
+
+  call assert_fails("wnext", "E1513:")
+  call assert_notequal(l:last, bufnr())
+
+  wnext!
+  call assert_equal(l:last, bufnr())
+
+  call delete("first")
+  call delete("middle")
+  call delete("last")
+endfunc
+
+" Fail :wprevious but :wprevious! is allowed
+func Test_wprevious()
+  call s:reset_all_buffers()
+
+  let [l:first, _] = s:make_args_list()
+  next!
+
+  call assert_fails("wprevious", "E1513:")
+  call assert_notequal(l:first, bufnr())
+
+  wprevious!
+  call assert_equal(l:first, bufnr())
+
+  call delete("first")
+  call delete("middle")
+  call delete("last")
+endfunc