vim-patch:9.1.0116: win_split_ins may not check available room

Problem:  win_split_ins has no check for E36 when moving an existing
          window
Solution: check for room and fix the issues in f_win_splitmove()
          (Sean Dewar)

https://github.com/vim/vim/commit/0fd44a5ad81ade342cb54d8984965bdedd2272c8

Omit WSP_FORCE_ROOM, as it's not needed for Nvim's autocmd window, which is
floating. Shouldn't be difficult to port later if it's used for anything else.

Make win_splitmove continue working for turning floating windows into splits.
Move the logic for "unfloating" a float to win_split_ins; unlike splits, no
changes to the window layout are needed before calling it, as floats take no
room in the window layout and cannot affect the e_noroom check.

Add missing tp_curwin-fixing logic for turning external windows into splits, and
add a test.
NOTE: there are other issues with the way "tabpage independence" is implemented
for external windows; namely, some things assume that tp_curwin is indeed a
window within that tabpage, and as such, functions like tabpage_winnr and
nvim_tabpage_get_win currently don't always work for external windows (with the
latter aborting!)

Use last_status over frame_add_statusline, as Nvim's last_status already does
this for all windows in the current tabpage. Adjust restore_full_snapshot_rec to
handle this.
This "restore everything" approach is changed in a future commit anyway, so only
ensure it's robust enough to just pass tests.

Keep check_split_disallowed's current doc comment, as it's actually a bit more
accurate here. (I should probably PR Vim to use this one)

Allow f_win_splitmove to move a floating "wp" into a split; Nvim supports this.
Continue to disallow it from moving the autocommand window into a split (funnily
enough, the check wasn't reachable before, as moving a float was disallowed),
but now return -1 in that case (win_splitmove also returns FAIL for this, but
handling it in f_win_splitmove avoids us needing to switch windows first).

Cherry-pick Test_window_split_no_room fix from v9.1.0121.

Update nvim_win_set_config to handle win_split_ins failure in later commits.

7 files changed, 389 insertions, 118 deletions

diff --git a/src/nvim/api/win_config.c b/src/nvim/api/win_config.c
index 8608b0dde9..c308cadb7c 100644
--- a/src/nvim/api/win_config.c
+++ b/src/nvim/api/win_config.c
@@ -526,18 +526,6 @@ void nvim_win_set_config(Window window, Dict(win_config) *config, Error *err)
       }
     } else {
       win_remove(win, win_tp == curtab ? NULL : win_tp);
-      ui_comp_remove_grid(&win->w_grid_alloc);
-      if (win->w_config.external) {
-        for (tabpage_T *tp = first_tabpage; tp != NULL; tp = tp->tp_next) {
-          if (tp == curtab) {
-            continue;
-          }
-          if (tp->tp_curwin == win) {
-            tp->tp_curwin = tp->tp_firstwin;
-          }
-        }
-      }
-      win->w_pos_changed = true;
     }
 
     int flags = win_split_flags(fconfig.split, parent == NULL) | WSP_NOENTER;
diff --git a/src/nvim/buffer.c b/src/nvim/buffer.c
index f6c7229485..b013f43ceb 100644
--- a/src/nvim/buffer.c
+++ b/src/nvim/buffer.c
@@ -117,7 +117,6 @@
 # include "buffer.c.generated.h"
 #endif
 
-static const char *e_auabort = N_("E855: Autocommands caused command to abort");
 static const char e_attempt_to_delete_buffer_that_is_in_use_str[]
   = N_("E937: Attempt to delete a buffer that is in use: %s");
 
diff --git a/src/nvim/eval/window.c b/src/nvim/eval/window.c
index b8aa0c9641..17b8b01963 100644
--- a/src/nvim/eval/window.c
+++ b/src/nvim/eval/window.c
@@ -659,55 +659,19 @@ void f_win_screenpos(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   tv_list_append_number(rettv->vval.v_list, wp == NULL ? 0 : wp->w_wincol + 1);
 }
 
-/// Move the window wp into a new split of targetwin in a given direction
-static void win_move_into_split(win_T *wp, win_T *targetwin, int size, int flags)
-{
-  int height = wp->w_height;
-  win_T *oldwin = curwin;
-
-  if (wp == targetwin || is_aucmd_win(wp)) {
-    return;
-  }
-
-  // Jump to the target window
-  if (curwin != targetwin) {
-    win_goto(targetwin);
-  }
-
-  // Remove the old window and frame from the tree of frames
-  int dir;
-  winframe_remove(wp, &dir, NULL);
-  win_remove(wp, NULL);
-  last_status(false);     // may need to remove last status line
-  win_comp_pos();   // recompute window positions
-
-  // Split a window on the desired side and put the old window there
-  win_split_ins(size, flags, wp, dir);
-
-  // If splitting horizontally, try to preserve height
-  if (size == 0 && !(flags & WSP_VERT)) {
-    win_setheight_win(height, wp);
-    if (p_ea) {
-      win_equal(wp, true, 'v');
-    }
-  }
-
-  if (oldwin != curwin) {
-    win_goto(oldwin);
-  }
-}
-
 /// "win_splitmove()" function
 void f_win_splitmove(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 {
   win_T *wp = find_win_by_nr_or_id(&argvars[0]);
   win_T *targetwin = find_win_by_nr_or_id(&argvars[1]);
+  win_T *oldwin = curwin;
+
+  rettv->vval.v_number = -1;
 
   if (wp == NULL || targetwin == NULL || wp == targetwin
       || !win_valid(wp) || !win_valid(targetwin)
-      || win_float_valid(wp) || win_float_valid(targetwin)) {
+      || targetwin->w_floating) {
     emsg(_(e_invalwindow));
-    rettv->vval.v_number = -1;
     return;
   }
 
@@ -732,7 +696,27 @@ void f_win_splitmove(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
     size = (int)tv_dict_get_number(d, "size");
   }
 
-  win_move_into_split(wp, targetwin, size, flags);
+  // Check if we can split the target before we bother switching windows.
+  if (is_aucmd_win(wp) || check_split_disallowed(targetwin) == FAIL) {
+    return;
+  }
+
+  if (curwin != targetwin) {
+    win_goto(targetwin);
+  }
+
+  // Autocommands may have sent us elsewhere or closed "wp" or "oldwin".
+  if (curwin == targetwin && win_valid(wp)) {
+    if (win_splitmove(wp, size, flags) == OK) {
+      rettv->vval.v_number = 0;
+    }
+  } else {
+    emsg(_(e_auabort));
+  }
+
+  if (oldwin != curwin && win_valid(oldwin)) {
+    win_goto(oldwin);
+  }
 }
 
 /// "win_gettype(nr)" function
diff --git a/src/nvim/globals.h b/src/nvim/globals.h
index 22f7daa823..c1c9ae456c 100644
--- a/src/nvim/globals.h
+++ b/src/nvim/globals.h
@@ -939,6 +939,7 @@ EXTERN const char e_using_float_as_string[] INIT(= N_("E806: Using a Float as a
 EXTERN const char e_cannot_edit_other_buf[] INIT(= N_("E788: Not allowed to edit another buffer now"));
 EXTERN const char e_using_number_as_bool_nr[] INIT(= N_("E1023: Using a Number as a Bool: %d"));
 EXTERN const char e_not_callable_type_str[] INIT(= N_("E1085: Not a callable type: %s"));
+EXTERN const char e_auabort[] INIT(= N_("E855: Autocommands caused command to abort"));
 
 EXTERN const char e_api_error[] INIT(= N_("E5555: API call: %s"));
 
diff --git a/src/nvim/window.c b/src/nvim/window.c
index 81f8304b22..cfa28bbc1f 100644
--- a/src/nvim/window.c
+++ b/src/nvim/window.c
@@ -455,9 +455,14 @@ newwindow:
   case 'H':
   case 'L':
     CHECK_CMDWIN;
-    win_totop(Prenum,
-              ((nchar == 'H' || nchar == 'L') ? WSP_VERT : 0)
-              | ((nchar == 'H' || nchar == 'K') ? WSP_TOP : WSP_BOT));
+    if (firstwin == curwin && lastwin_nofloating() == curwin) {
+      beep_flush();
+    } else {
+      const int dir = ((nchar == 'H' || nchar == 'L') ? WSP_VERT : 0)
+                      | ((nchar == 'H' || nchar == 'K') ? WSP_TOP : WSP_BOT);
+
+      win_splitmove(curwin, Prenum, dir);
+    }
     break;
 
   // make all windows the same width and/or height
@@ -907,7 +912,7 @@ void ui_ext_win_viewport(win_T *wp)
 
 /// If "split_disallowed" is set or "wp"s buffer is closing, give an error and return FAIL.
 /// Otherwise return OK.
-static int check_split_disallowed(const win_T *wp)
+int check_split_disallowed(const win_T *wp)
   FUNC_ATTR_NONNULL_ALL
 {
   Error err = ERROR_INIT;
@@ -1004,13 +1009,12 @@ win_T *win_split_ins(int size, int flags, win_T *new_wp, int dir)
 
   int need_status = 0;
   int new_size = size;
-  bool new_in_layout = (new_wp == NULL || new_wp->w_floating);
   bool vertical = flags & WSP_VERT;
   bool toplevel = flags & (WSP_TOP | WSP_BOT);
 
   // add a status line when p_ls == 1 and splitting the first window
   if (one_nonfloat() && p_ls == 1 && oldwin->w_status_height == 0) {
-    if (oldwin->w_height <= p_wmh && new_in_layout) {
+    if (oldwin->w_height <= p_wmh) {
       emsg(_(e_noroom));
       return NULL;
     }
@@ -1059,7 +1063,7 @@ win_T *win_split_ins(int size, int flags, win_T *new_wp, int dir)
       available = oldwin->w_frame->fr_width;
       needed += minwidth;
     }
-    if (available < needed && new_in_layout) {
+    if (available < needed) {
       emsg(_(e_noroom));
       return NULL;
     }
@@ -1139,7 +1143,7 @@ win_T *win_split_ins(int size, int flags, win_T *new_wp, int dir)
       available = oldwin->w_frame->fr_height;
       needed += minheight;
     }
-    if (available < needed && new_in_layout) {
+    if (available < needed) {
       emsg(_(e_noroom));
       return NULL;
     }
@@ -1229,8 +1233,27 @@ win_T *win_split_ins(int size, int flags, win_T *new_wp, int dir)
     // make the contents of the new window the same as the current one
     win_init(wp, curwin, flags);
   } else if (wp->w_floating) {
-    new_frame(wp);
+    ui_comp_remove_grid(&wp->w_grid_alloc);
+    if (ui_has(kUIMultigrid)) {
+      wp->w_pos_changed = true;
+    } else {
+      // No longer a float, a non-multigrid UI shouldn't draw it as such
+      ui_call_win_hide(wp->w_grid_alloc.handle);
+      win_free_grid(wp, true);
+    }
+
+    // External windows are independent of tabpages, and may have been the curwin of others.
+    if (wp->w_config.external) {
+      FOR_ALL_TABS(tp) {
+        if (tp != curtab && tp->tp_curwin == wp) {
+          tp->tp_curwin = tp->tp_firstwin;
+        }
+      }
+    }
+
     wp->w_floating = false;
+    new_frame(wp);
+
     // non-floating window doesn't store float config or have a border.
     wp->w_config = WIN_CONFIG_INIT;
     CLEAR_FIELD(wp->w_border_adj);
@@ -1874,48 +1897,67 @@ static void win_rotate(bool upwards, int count)
   redraw_all_later(UPD_NOT_VALID);
 }
 
-// Move the current window to the very top/bottom/left/right of the screen.
-static void win_totop(int size, int flags)
+/// Move "wp" into a new split in a given direction, possibly relative to the
+/// current window.
+/// "wp" must be valid in the current tabpage.
+/// Returns FAIL for failure, OK otherwise.
+int win_splitmove(win_T *wp, int size, int flags)
 {
   int dir = 0;
-  int height = curwin->w_height;
+  int height = wp->w_height;
 
-  if (firstwin == curwin && lastwin_nofloating() == curwin) {
-    beep_flush();
-    return;
-  }
-  if (is_aucmd_win(curwin)) {
-    return;
+  if (firstwin == wp && lastwin_nofloating() == wp) {
+    return OK;  // nothing to do
   }
-  if (check_split_disallowed(curwin) == FAIL) {
-    return;
+  if (is_aucmd_win(wp) || check_split_disallowed(wp) == FAIL) {
+    return FAIL;
   }
 
-  if (curwin->w_floating) {
-    ui_comp_remove_grid(&curwin->w_grid_alloc);
-    if (ui_has(kUIMultigrid)) {
-      curwin->w_pos_changed = true;
-    } else {
-      // No longer a float, a non-multigrid UI shouldn't draw it as such
-      ui_call_win_hide(curwin->w_grid_alloc.handle);
-      win_free_grid(curwin, true);
-    }
+  frame_T *frp = NULL;
+  if (wp->w_floating) {
+    win_remove(wp, NULL);
   } else {
+    // Undoing changes to frames if splitting fails is complicated.
+    // Save a full snapshot to restore instead.
+    frp = make_full_snapshot();
+
     // Remove the window and frame from the tree of frames.
-    winframe_remove(curwin, &dir, NULL);
+    winframe_remove(wp, &dir, NULL);
+    win_remove(wp, NULL);
+    last_status(false);  // may need to remove last status line
+    win_comp_pos();  // recompute window positions
+  }
+
+  // Split a window on the desired side and put "wp" there.
+  if (win_split_ins(size, flags, wp, dir) == NULL) {
+    win_append(wp->w_prev, wp);
+    if (!wp->w_floating) {
+      // Restore the previous layout from the snapshot.
+      xfree(wp->w_frame);
+      restore_full_snapshot(frp);
+
+      // Vertical separators to the left may have been lost.  Restore them.
+      frp = wp->w_frame;
+      if (frp->fr_parent->fr_layout == FR_ROW && frp->fr_prev != NULL) {
+        frame_add_vsep(frp->fr_prev);
+      }
+    }
+    return FAIL;
   }
-  win_remove(curwin, NULL);
-  last_status(false);       // may need to remove last status line
-  win_comp_pos();     // recompute window positions
+  clear_snapshot_rec(frp);
 
-  // Split a window on the desired side and put the window there.
-  win_split_ins(size, flags, curwin, dir);
-  if (!(flags & WSP_VERT)) {
-    win_setheight(height);
+  // If splitting horizontally, try to preserve height.
+  // Note that win_split_ins autocommands may have immediately made "wp" floating!
+  if (size == 0 && !(flags & WSP_VERT) && !wp->w_floating) {
+    win_setheight_win(height, wp);
     if (p_ea) {
-      win_equal(curwin, true, 'v');
+      // Equalize windows.  Note that win_split_ins autocommands may have
+      // made a window other than "wp" current.
+      win_equal(curwin, curwin == wp, 'v');
     }
   }
+
+  return OK;
 }
 
 // Move window "win1" to below/right of "win2" and make "win1" the current
@@ -2777,13 +2819,10 @@ int win_close(win_T *win, bool free_buf, bool force)
     ui_comp_remove_grid(&win->w_grid_alloc);
     assert(first_tabpage != NULL);  // suppress clang "Dereference of NULL pointer"
     if (win->w_config.external) {
-      for (tabpage_T *tp = first_tabpage; tp != NULL; tp = tp->tp_next) {
-        if (tp == curtab) {
-          continue;
-        }
-        if (tp->tp_curwin == win) {
+      FOR_ALL_TABS(tp) {
+        if (tp != curtab && tp->tp_curwin == win) {
           // NB: an autocmd can still abort the closing of this window,
-          // bur carring out this change anyway shouldn't be a catastrophe.
+          // but carrying out this change anyway shouldn't be a catastrophe.
           tp->tp_curwin = tp->tp_firstwin;
         }
       }
@@ -7207,23 +7246,23 @@ void reset_lnums(void)
 void make_snapshot(int idx)
 {
   clear_snapshot(curtab, idx);
-  make_snapshot_rec(topframe, &curtab->tp_snapshot[idx]);
+  make_snapshot_rec(topframe, &curtab->tp_snapshot[idx], false);
 }
 
-static void make_snapshot_rec(frame_T *fr, frame_T **frp)
+static void make_snapshot_rec(frame_T *fr, frame_T **frp, bool snap_wins)
 {
   *frp = xcalloc(1, sizeof(frame_T));
   (*frp)->fr_layout = fr->fr_layout;
   (*frp)->fr_width = fr->fr_width;
   (*frp)->fr_height = fr->fr_height;
   if (fr->fr_next != NULL) {
-    make_snapshot_rec(fr->fr_next, &((*frp)->fr_next));
+    make_snapshot_rec(fr->fr_next, &((*frp)->fr_next), snap_wins);
   }
   if (fr->fr_child != NULL) {
-    make_snapshot_rec(fr->fr_child, &((*frp)->fr_child));
+    make_snapshot_rec(fr->fr_child, &((*frp)->fr_child), snap_wins);
   }
-  if (fr->fr_layout == FR_LEAF && fr->fr_win == curwin) {
-    (*frp)->fr_win = curwin;
+  if (fr->fr_layout == FR_LEAF && (snap_wins || fr->fr_win == curwin)) {
+    (*frp)->fr_win = fr->fr_win;
   }
 }
 
@@ -7340,6 +7379,80 @@ static win_T *restore_snapshot_rec(frame_T *sn, frame_T *fr)
   return wp;
 }
 
+/// Return a snapshot of all frames in the current tabpage and which windows are
+/// in them.
+/// Use clear_snapshot_rec to free the snapshot.
+static frame_T *make_full_snapshot(void)
+{
+  frame_T *frp;
+  make_snapshot_rec(topframe, &frp, true);
+  return frp;
+}
+
+/// Restore all frames in the full snapshot "sn" for the current tabpage.
+/// Caller must ensure that the screen size didn't change, no windows with frames
+/// in the snapshot were freed, and windows with frames not in the snapshot are
+/// removed from their frames!
+/// Doesn't restore changed window vertical separators.
+/// Frees the old frames.  Don't call clear_snapshot_rec on "sn" afterwards!
+static void restore_full_snapshot(frame_T *sn)
+{
+  if (sn == NULL) {
+    return;
+  }
+
+  clear_snapshot_rec(topframe);
+  restore_full_snapshot_rec(sn);
+  curtab->tp_topframe = topframe = sn;
+  last_status(false);
+
+  // If the amount of space available changed, first try setting the sizes of
+  // windows with 'winfix{width,height}'. If that doesn't result in the right
+  // size, forget about that option.
+  if (topframe->fr_width != Columns) {
+    frame_new_width(topframe, Columns, false, true);
+    if (!frame_check_width(topframe, Columns)) {
+      frame_new_width(topframe, Columns, false, false);
+    }
+  }
+  if (topframe->fr_height != ROWS_AVAIL) {
+    frame_new_height(topframe, (int)ROWS_AVAIL, false, true);
+    if (!frame_check_height(topframe, (int)ROWS_AVAIL)) {
+      frame_new_height(topframe, (int)ROWS_AVAIL, false, false);
+    }
+  }
+
+  win_comp_pos();
+}
+
+static void restore_full_snapshot_rec(frame_T *sn)
+{
+  if (sn == NULL) {
+    return;
+  }
+
+  if (sn->fr_child != NULL) {
+    sn->fr_child->fr_parent = sn;
+  }
+  if (sn->fr_next != NULL) {
+    sn->fr_next->fr_parent = sn->fr_parent;
+    sn->fr_next->fr_prev = sn;
+  }
+  if (sn->fr_win != NULL) {
+    sn->fr_win->w_frame = sn;
+    // Assume for now that all windows have statuslines, so last_status in restore_full_snapshot
+    // doesn't resize frames to fit any missing statuslines.
+    sn->fr_win->w_status_height = STATUS_HEIGHT;
+    sn->fr_win->w_hsep_height = 0;
+
+    // Resize window to fit the frame.
+    frame_new_height(sn, sn->fr_height, false, false);
+    frame_new_width(sn, sn->fr_width, false, false);
+  }
+  restore_full_snapshot_rec(sn->fr_child);
+  restore_full_snapshot_rec(sn->fr_next);
+}
+
 /// Check that "topfrp" and its children are at the right height.
 ///
 /// @param  topfrp  top frame pointer
diff --git a/test/functional/ui/float_spec.lua b/test/functional/ui/float_spec.lua
index cdb3b79963..e324d03b30 100644
--- a/test/functional/ui/float_spec.lua
+++ b/test/functional/ui/float_spec.lua
@@ -550,6 +550,43 @@ describe('float window', function()
     eq({ w0 }, api.nvim_list_wins())
   end)
 
+  it('win_splitmove() can move float into a split', function()
+    command('split')
+    eq({'col', {{'leaf', 1001}, {'leaf', 1000}}}, fn.winlayout())
+
+    local win1 = api.nvim_open_win(0, true, {relative = 'editor', row = 1, col = 1, width = 5, height = 5})
+    fn.win_splitmove(win1, 1001, {vertical = true})
+    eq({'col', {{'row', {{'leaf', win1}, {'leaf', 1001}}}, {'leaf', 1000}}}, fn.winlayout())
+    eq('', api.nvim_win_get_config(win1).relative)
+
+    -- Should be unable to create a split relative to a float, though.
+    local win2 = api.nvim_open_win(0, true, {relative = 'editor', row = 1, col = 1, width = 5, height = 5})
+    eq('Vim:E957: Invalid window number', pcall_err(fn.win_splitmove, win1, win2, {vertical = true}))
+  end)
+
+  it('tp_curwin updated if external window is moved into split', function()
+    local screen = Screen.new(20, 7)
+    screen:attach { ext_multigrid = true }
+
+    command('tabnew')
+    local external_win = api.nvim_open_win(0, true, {external = true, width = 5, height = 5})
+    eq(external_win, api.nvim_get_current_win())
+    eq(2, fn.tabpagenr())
+    command('tabfirst')
+    api.nvim_set_current_win(external_win)
+    eq(external_win, api.nvim_get_current_win())
+    eq(1, fn.tabpagenr())
+
+    command('wincmd J')
+    eq(external_win, api.nvim_get_current_win())
+    eq(false, api.nvim_win_get_config(external_win).external)
+    command('tabnext')
+    eq(2, fn.tabpagenr())
+    neq(external_win, api.nvim_get_current_win())
+
+    screen:detach()
+  end)
+
   describe('with only one tabpage,', function()
     local float_opts = {relative = 'editor', row = 1, col = 1, width = 1, height = 1}
     local old_buf, old_win
@@ -9101,6 +9138,22 @@ describe('float window', function()
         ]]}
       end
     end)
+
+    it('attempt to turn into split with no room', function()
+      eq('Vim(split):E36: Not enough room', pcall_err(command, 'execute "split |"->repeat(&lines)'))
+      command('vsplit | wincmd | | wincmd p')
+      api.nvim_open_win(0, true, {relative = "editor", row = 0, col = 0, width = 5, height = 5})
+      local config = api.nvim_win_get_config(0)
+      eq('editor', config.relative)
+
+      local layout = fn.winlayout()
+      local restcmd = fn.winrestcmd()
+      eq('Vim(wincmd):E36: Not enough room', pcall_err(command, 'wincmd K'))
+      eq('Vim(wincmd):E36: Not enough room', pcall_err(command, 'wincmd J'))
+      eq(layout, fn.winlayout())
+      eq(restcmd, fn.winrestcmd())
+      eq(config, api.nvim_win_get_config(0))
+    end)
   end
 
   describe('with ext_multigrid', function()
diff --git a/test/old/testdir/test_window_cmd.vim b/test/old/testdir/test_window_cmd.vim
index da1711a0a1..99a713d2ed 100644
--- a/test/old/testdir/test_window_cmd.vim
+++ b/test/old/testdir/test_window_cmd.vim
@@ -272,6 +272,16 @@ func Test_window_split_no_room()
   for s in range(1, hor_split_count) | split | endfor
   call assert_fails('split', 'E36:')
 
+  botright vsplit
+  wincmd |
+  let layout = winlayout()
+  let restcmd = winrestcmd()
+  call assert_fails('wincmd J', 'E36:')
+  call assert_fails('wincmd K', 'E36:')
+  call assert_equal(layout, winlayout())
+  call assert_equal(restcmd, winrestcmd())
+  only
+
   " N vertical windows need >= 2*(N - 1) + 1 columns:
   " - 1 column + 1 separator for each window (except last window)
   " - 1 column for the last window which does not have separator
@@ -284,7 +294,39 @@ func Test_window_split_no_room()
   for s in range(1, ver_split_count) | vsplit | endfor
   call assert_fails('vsplit', 'E36:')
 
+  split
+  wincmd |
+  let layout = winlayout()
+  let restcmd = winrestcmd()
+  call assert_fails('wincmd H', 'E36:')
+  call assert_fails('wincmd L', 'E36:')
+  call assert_equal(layout, winlayout())
+  call assert_equal(restcmd, winrestcmd())
+
+  " Check that the last statusline isn't lost.
+  " Set its window's width to 2 for the test.
+  wincmd j
+  set laststatus=0 winminwidth=0
+  vertical resize 2
+  set winminwidth&
+  call setwinvar(winnr('k'), '&statusline', '@#')
+  let last_stl_row = win_screenpos(0)[0] - 1
+  redraw
+  call assert_equal('@#|', GetScreenStr(last_stl_row))
+  call assert_equal('~ |', GetScreenStr(&lines - &cmdheight))
+
+  let restcmd = winrestcmd()
+  call assert_fails('wincmd H', 'E36:')
+  call assert_fails('wincmd L', 'E36:')
+  call assert_equal(layout, winlayout())
+  call assert_equal(restcmd, winrestcmd())
+  call setwinvar(winnr('k'), '&statusline', '=-')
+  redraw
+  call assert_equal('=-|', GetScreenStr(last_stl_row))
+  call assert_equal('~ |', GetScreenStr(&lines - &cmdheight))
+
   %bw!
+  set laststatus&
 endfunc
 
 func Test_window_exchange()
@@ -1055,6 +1097,44 @@ func Test_win_splitmove()
   tabnew
   call assert_fails('call win_splitmove(1, win_getid(1, 1))', 'E957:')
   tabclose
+
+  split
+  augroup WinSplitMove
+    au!
+    au WinEnter * ++once call win_gotoid(win_getid(winnr('#')))
+  augroup END
+  call assert_fails('call win_splitmove(winnr(), winnr("#"))', 'E855:')
+
+  augroup WinSplitMove
+    au!
+    au WinLeave * ++once quit
+  augroup END
+  call assert_fails('call win_splitmove(winnr(), winnr("#"))', 'E855:')
+
+  split
+  split
+  augroup WinSplitMove
+    au!
+    au WinEnter * ++once let s:triggered = v:true
+          \| call assert_fails('call win_splitmove(winnr("$"), winnr())', 'E242:')
+  augroup END
+  quit
+  call assert_equal(v:true, s:triggered)
+  unlet! s:triggered
+
+  new
+  augroup WinSplitMove
+    au!
+    au BufHidden * ++once let s:triggered = v:true
+          \| call assert_fails('call win_splitmove(winnr("#"), winnr())', 'E1159:')
+  augroup END
+  hide
+  call assert_equal(v:true, s:triggered)
+  unlet! s:triggered
+
+  au! WinSplitMove
+  augroup! WinSplitMove
+  %bw!
 endfunc
 
 func Test_floatwin_splitmove()
@@ -1062,7 +1142,8 @@ func Test_floatwin_splitmove()
   let win2 = win_getid()
   let popup_winid = nvim_open_win(0, 0, {'relative': 'win',
         \ 'row': 3, 'col': 3, 'width': 12, 'height': 3})
-  call assert_fails('call win_splitmove(popup_winid, win2)', 'E957:')
+  " Nvim: floating windows are supported for the first argument.
+  " call assert_fails('call win_splitmove(popup_winid, win2)', 'E957:')
   call assert_fails('call win_splitmove(win2, popup_winid)', 'E957:')
 
   call nvim_win_close(popup_winid, 1)
@@ -2007,23 +2088,75 @@ func Test_new_help_window_on_error()
 endfunc
 
 func Test_smoothscroll_in_zero_width_window()
-  let save_lines = &lines
-  let save_columns = &columns
+  set cpo+=n number smoothscroll
+  set winwidth=99999 winminwidth=0
 
-  winsize 0 24
-  set cpo+=n
-  exe "noremap 0 \<C-W>n\<C-W>L"
-  norm 000000
-  set number smoothscroll
-  exe "norm \<C-Y>"
+  vsplit
+  call assert_equal(0, winwidth(winnr('#')))
+  call win_execute(win_getid(winnr('#')), "norm! \<C-Y>")
 
   only!
-  let &lines = save_lines
-  let &columns = save_columns
-  set cpo-=n
-  unmap 0
-  set nonumber nosmoothscroll
+  set winwidth& winminwidth&
+  set cpo-=n nonumber nosmoothscroll
 endfunc
 
+func Test_splitmove_flatten_frame()
+  split
+  vsplit
+
+  wincmd L
+  let layout = winlayout()
+  wincmd K
+  wincmd L
+  call assert_equal(winlayout(), layout)
+
+  only!
+endfunc
+
+func Test_splitmove_autocmd_window_no_room()
+  " Open as many windows as possible
+  while v:true
+    try
+      split
+    catch /E36:/
+      break
+    endtry
+  endwhile
+  while v:true
+    try
+      vsplit
+    catch /E36:/
+      break
+    endtry
+  endwhile
+
+  wincmd j
+  vsplit
+  call assert_fails('wincmd H', 'E36:')
+  call assert_fails('wincmd J', 'E36:')
+  call assert_fails('wincmd K', 'E36:')
+  call assert_fails('wincmd L', 'E36:')
+
+  edit unload me
+  enew
+  bunload! unload\ me
+  augroup SplitMoveAucmdWin
+    au!
+    au BufEnter * ++once let s:triggered = v:true
+                      \| call assert_equal('autocmd', win_gettype())
+  augroup END
+  let layout = winlayout()
+  let restcmd = winrestcmd()
+  " bufload opening the autocommand window shouldn't give E36.
+  call bufload('unload me')
+  call assert_equal(v:true, s:triggered)
+  call assert_equal(winlayout(), layout)
+  call assert_equal(winrestcmd(), restcmd)
+
+  unlet! s:triggered
+  au! SplitMoveAucmdWin
+  augroup! SplitMoveAucmdWin
+  %bw!
+endfunc
 
 " vim: shiftwidth=2 sts=2 expandtab