vim-patch:8.1.0514: CTRL-W ^ does not work when alternate buffer has no name

Problem:    CTRL-W ^ does not work when alternate buffer has no name.
Solution:   Use another method to split and edit the alternate buffer. (Jason
            Franklin)
https://github.com/vim/vim/commit/1bbb61948342b5cf6e363629f145c65eb455c388

5 files changed, 176 insertions, 76 deletions

diff --git a/runtime/doc/windows.txt b/runtime/doc/windows.txt
index 76bb096ee3..977e0daef7 100644
--- a/runtime/doc/windows.txt
+++ b/runtime/doc/windows.txt
@@ -201,9 +201,11 @@ CTRL-W CTRL_N						*CTRL-W_CTRL-N*
 		|:find|.  Doesn't split if {file} is not found.
 
 CTRL-W CTRL-^					*CTRL-W_CTRL-^* *CTRL-W_^*
-CTRL-W ^	Does ":split #", split window in two and edit alternate file.
-		When a count is given, it becomes ":split #N", split window
-		and edit buffer N.
+CTRL-W ^	Split the current window in two and edit the alternate file.
+		When a count N is given, split the current window and edit
+		buffer N.  Similar to ":sp #" and ":sp #N", but it allows the
+		other buffer to be unnamed.  This command matches the behavior
+		of |CTRL-^|, except that it splits a window first.
 
 CTRL-W ge						*CTRL-W_ge*
 		Detach the current window as an external window.
diff --git a/src/nvim/normal.c b/src/nvim/normal.c
index 6b76082772..e32b738c7e 100644
--- a/src/nvim/normal.c
+++ b/src/nvim/normal.c
@@ -4680,9 +4680,8 @@ static void nv_ctrlo(cmdarg_T *cap)
   }
 }
 
-/*
- * CTRL-^ command, short for ":e #"
- */
+// CTRL-^ command, short for ":e #".  Works even when the alternate buffer is
+// not named.
 static void nv_hat(cmdarg_T *cap)
 {
   if (!checkclearopq(cap->oap))
diff --git a/src/nvim/testdir/test_normal.vim b/src/nvim/testdir/test_normal.vim
index 0c71e2af4c..b3e43640bb 100644
--- a/src/nvim/testdir/test_normal.vim
+++ b/src/nvim/testdir/test_normal.vim
@@ -2,12 +2,12 @@
 
 source shared.vim
 
-func! Setup_NewWindow()
+func Setup_NewWindow()
   10new
   call setline(1, range(1,100))
 endfunc
 
-func! MyFormatExpr()
+func MyFormatExpr()
   " Adds '->$' at lines having numbers followed by trailing whitespace
   for ln in range(v:lnum, v:lnum+v:count-1)
     let line = getline(ln)
@@ -17,7 +17,7 @@ func! MyFormatExpr()
   endfor
 endfunc
 
-func! CountSpaces(type, ...)
+func CountSpaces(type, ...)
   " for testing operatorfunc
   " will count the number of spaces
   " and return the result in g:a
@@ -37,7 +37,7 @@ func! CountSpaces(type, ...)
   let @@ = reg_save
 endfunc
 
-func! OpfuncDummy(type, ...)
+func OpfuncDummy(type, ...)
   " for testing operatorfunc
   let g:opt=&linebreak
 
@@ -81,7 +81,7 @@ fun! Test_normal00_optrans()
   bw!
 endfunc
 
-func! Test_normal01_keymodel()
+func Test_normal01_keymodel()
   call Setup_NewWindow()
   " Test 1: depending on 'keymodel' <s-down> does something different
   50
@@ -115,7 +115,7 @@ func! Test_normal01_keymodel()
   bw!
 endfunc
 
-func! Test_normal02_selectmode()
+func Test_normal02_selectmode()
   " some basic select mode tests
   call Setup_NewWindow()
   50
@@ -129,7 +129,7 @@ func! Test_normal02_selectmode()
   bw!
 endfunc
 
-func! Test_normal02_selectmode2()
+func Test_normal02_selectmode2()
   " some basic select mode tests
   call Setup_NewWindow()
   50
@@ -139,7 +139,7 @@ func! Test_normal02_selectmode2()
   bw!
 endfunc
 
-func! Test_normal03_join()
+func Test_normal03_join()
   " basic join test
   call Setup_NewWindow()
   50
@@ -159,7 +159,7 @@ func! Test_normal03_join()
   bw!
 endfunc
 
-func! Test_normal04_filter()
+func Test_normal04_filter()
   " basic filter test
   " only test on non windows platform
   if has('win32')
@@ -185,7 +185,7 @@ func! Test_normal04_filter()
   bw!
 endfunc
 
-func! Test_normal05_formatexpr()
+func Test_normal05_formatexpr()
   " basic formatexpr test
   call Setup_NewWindow()
   %d_
@@ -222,7 +222,7 @@ func Test_normal05_formatexpr_setopt()
   set formatexpr=
 endfunc
 
-func! Test_normal06_formatprg()
+func Test_normal06_formatprg()
   " basic test for formatprg
   " only test on non windows platform
   if has('win32')
@@ -256,7 +256,7 @@ func! Test_normal06_formatprg()
   call delete('Xsed_format.sh')
 endfunc
 
-func! Test_normal07_internalfmt()
+func Test_normal07_internalfmt()
   " basic test for internal formmatter to textwidth of 12
   let list=range(1,11)
   call map(list, 'v:val."    "')
@@ -270,7 +270,7 @@ func! Test_normal07_internalfmt()
   bw!
 endfunc
 
-func! Test_normal08_fold()
+func Test_normal08_fold()
   " basic tests for foldopen/folddelete
   if !has("folding")
     return
@@ -329,7 +329,7 @@ func! Test_normal08_fold()
   bw!
 endfunc
 
-func! Test_normal09_operatorfunc()
+func Test_normal09_operatorfunc()
   " Test operatorfunc
   call Setup_NewWindow()
   " Add some spaces for counting
@@ -359,7 +359,7 @@ func! Test_normal09_operatorfunc()
   bw!
 endfunc
 
-func! Test_normal09a_operatorfunc()
+func Test_normal09a_operatorfunc()
   " Test operatorfunc
   call Setup_NewWindow()
   " Add some spaces for counting
@@ -385,7 +385,7 @@ func! Test_normal09a_operatorfunc()
   unlet! g:opt
 endfunc
 
-func! Test_normal10_expand()
+func Test_normal10_expand()
   " Test for expand()
   10new
   call setline(1, ['1', 'ifooar,,cbar'])
@@ -420,7 +420,7 @@ func! Test_normal10_expand()
   bw!
 endfunc
 
-func! Test_normal11_showcmd()
+func Test_normal11_showcmd()
   " test for 'showcmd'
   10new
   exe "norm! ofoobar\<esc>"
@@ -435,7 +435,7 @@ func! Test_normal11_showcmd()
   bw!
 endfunc
 
-func! Test_normal12_nv_error()
+func Test_normal12_nv_error()
   " Test for nv_error
   10new
   call setline(1, range(1,5))
@@ -445,7 +445,7 @@ func! Test_normal12_nv_error()
   bw!
 endfunc
 
-func! Test_normal13_help()
+func Test_normal13_help()
   " Test for F1
   call assert_equal(1, winnr())
   call feedkeys("\<f1>", 'txi')
@@ -454,7 +454,7 @@ func! Test_normal13_help()
   bw!
 endfunc
 
-func! Test_normal14_page()
+func Test_normal14_page()
   " basic test for Ctrl-F and Ctrl-B
   call Setup_NewWindow()
   exe "norm! \<c-f>"
@@ -488,7 +488,7 @@ func! Test_normal14_page()
   bw!
 endfunc
 
-func! Test_normal14_page_eol()
+func Test_normal14_page_eol()
   10new
   norm oxxxxxxx
   exe "norm 2\<c-f>"
@@ -497,7 +497,7 @@ func! Test_normal14_page_eol()
   bw!
 endfunc
 
-func! Test_normal15_z_scroll_vert()
+func Test_normal15_z_scroll_vert()
   " basic test for z commands that scroll the window
   call Setup_NewWindow()
   100
@@ -586,7 +586,7 @@ func! Test_normal15_z_scroll_vert()
   bw!
 endfunc
 
-func! Test_normal16_z_scroll_hor()
+func Test_normal16_z_scroll_hor()
   " basic test for z commands that scroll the window
   10new
   15vsp
@@ -652,7 +652,7 @@ func! Test_normal16_z_scroll_hor()
   bw!
 endfunc
 
-func! Test_normal17_z_scroll_hor2()
+func Test_normal17_z_scroll_hor2()
   " basic test for z commands that scroll the window
   " using 'sidescrolloff' setting
   10new
@@ -719,7 +719,7 @@ func! Test_normal17_z_scroll_hor2()
   bw!
 endfunc
 
-func! Test_normal18_z_fold()
+func Test_normal18_z_fold()
   " basic tests for foldopen/folddelete
   if !has("folding")
     return
@@ -1090,7 +1090,7 @@ func! Test_normal18_z_fold()
   bw!
 endfunc
 
-func! Test_normal19_z_spell()
+func Test_normal19_z_spell()
   if !has("spell") || !has('syntax')
     return
   endif
@@ -1245,7 +1245,7 @@ func! Test_normal19_z_spell()
   bw!
 endfunc
 
-func! Test_normal20_exmode()
+func Test_normal20_exmode()
   if !has("unix")
     " Reading from redirected file doesn't work on MS-Windows
     return
@@ -1263,24 +1263,38 @@ func! Test_normal20_exmode()
   bw!
 endfunc
 
-func! Test_normal21_nv_hat()
-  set hidden
-  new
-  " to many buffers opened already, will not work
-  "call assert_fails(":b#", 'E23')
-  "call assert_equal('', @#)
-  e Xfoobar
-  e Xfile2
-  call feedkeys("\<c-^>", 't')
-  call assert_equal("Xfile2", fnamemodify(bufname('%'), ':t'))
-  call feedkeys("f\<c-^>", 't')
-  call assert_equal("Xfile2", fnamemodify(bufname('%'), ':t'))
-  " clean up
-  set nohidden
-  bw!
+func Test_normal21_nv_hat()
+
+  " Edit a fresh file and wipe the buffer list so that there is no alternate
+  " file present.  Next, check for the expected command failures.
+  edit Xfoo | %bw
+  call assert_fails(':buffer #', 'E86')
+  call assert_fails(':execute "normal! \<C-^>"', 'E23')
+
+  " Test for the expected behavior when switching between two named buffers.
+  edit Xfoo | edit Xbar
+  call feedkeys("\<C-^>", 'tx')
+  call assert_equal('Xfoo', fnamemodify(bufname('%'), ':t'))
+  call feedkeys("\<C-^>", 'tx')
+  call assert_equal('Xbar', fnamemodify(bufname('%'), ':t'))
+
+  " Test for the expected behavior when only one buffer is named.
+  enew | let l:nr = bufnr('%')
+  call feedkeys("\<C-^>", 'tx')
+  call assert_equal('Xbar', fnamemodify(bufname('%'), ':t'))
+  call feedkeys("\<C-^>", 'tx')
+  call assert_equal('', bufname('%'))
+  call assert_equal(l:nr, bufnr('%'))
+
+  " Test that no action is taken by "<C-^>" when an operator is pending.
+  edit Xfoo
+  call feedkeys("ci\<C-^>", 'tx')
+  call assert_equal('Xfoo', fnamemodify(bufname('%'), ':t'))
+
+  %bw!
 endfunc
 
-func! Test_normal22_zet()
+func Test_normal22_zet()
   " Test for ZZ
   " let shell = &shell
   " let &shell = 'sh'
@@ -1308,7 +1322,7 @@ func! Test_normal22_zet()
   " let &shell = shell
 endfunc
 
-func! Test_normal23_K()
+func Test_normal23_K()
   " Test for K command
   new
   call append(0, ['helphelp.txt', 'man', 'aa%bb', 'cc|dd'])
@@ -1373,7 +1387,7 @@ func! Test_normal23_K()
   bw!
 endfunc
 
-func! Test_normal24_rot13()
+func Test_normal24_rot13()
   " Testing for g?? g?g?
   new
   call append(0, 'abcdefghijklmnopqrstuvwxyzäüö')
@@ -1387,7 +1401,7 @@ func! Test_normal24_rot13()
   bw!
 endfunc
 
-func! Test_normal25_tag()
+func Test_normal25_tag()
   " Testing for CTRL-] g CTRL-] g]
   " CTRL-W g] CTRL-W CTRL-] CTRL-W g CTRL-]
   h
@@ -1454,7 +1468,7 @@ func! Test_normal25_tag()
   helpclose
 endfunc
 
-func! Test_normal26_put()
+func Test_normal26_put()
   " Test for ]p ]P [p and [P
   new
   call append(0, ['while read LINE', 'do', '  ((count++))', '  if [ $? -ne 0 ]; then', "    echo 'Error writing file'", '  fi', 'done'])
@@ -1473,7 +1487,7 @@ func! Test_normal26_put()
   bw!
 endfunc
 
-func! Test_normal27_bracket()
+func Test_normal27_bracket()
   " Test for [' [` ]' ]`
   call Setup_NewWindow()
   1,21s/.\+/  &   b/
@@ -1524,7 +1538,7 @@ func! Test_normal27_bracket()
   bw!
 endfunc
 
-func! Test_normal28_parenthesis()
+func Test_normal28_parenthesis()
   " basic testing for ( and )
   new
   call append(0, ['This is a test. With some sentences!', '', 'Even with a question? And one more. And no sentence here'])
@@ -1718,7 +1732,7 @@ fun! Test_normal31_r_cmd()
   bw!
 endfunc
 
-func! Test_normal32_g_cmd1()
+func Test_normal32_g_cmd1()
   " Test for g*, g#
   new
   call append(0, ['abc.x_foo', 'x_foobar.abc'])
@@ -1849,7 +1863,7 @@ fun! Test_normal33_g_cmd2()
   bw!
 endfunc
 
-func! Test_g_ctrl_g()
+func Test_g_ctrl_g()
   new
 
   let a = execute(":norm! g\<c-g>")
@@ -2139,7 +2153,7 @@ fun! Test_normal41_insert_reg()
   bw!
 endfunc
 
-func! Test_normal42_halfpage()
+func Test_normal42_halfpage()
   " basic test for Ctrl-D and Ctrl-U
   call Setup_NewWindow()
   call assert_equal(5, &scroll)
@@ -2207,7 +2221,7 @@ fun! Test_normal43_textobject1()
   bw!
 endfunc
 
-func! Test_normal44_textobjects2()
+func Test_normal44_textobjects2()
   " basic testing for is and as text objects
   new
   call append(0, ['This is a test. With some sentences!', '', 'Even with a question? And one more. And no sentence here'])
@@ -2262,7 +2276,7 @@ func! Test_normal44_textobjects2()
   bw!
 endfunc
 
-func! Test_normal45_drop()
+func Test_normal45_drop()
   if !has('dnd')
     " The ~ register does not exist
     call assert_beeps('norm! "~')
@@ -2280,7 +2294,7 @@ func! Test_normal45_drop()
   bw!
 endfunc
 
-func! Test_normal46_ignore()
+func Test_normal46_ignore()
   new
   " How to test this?
   " let's just for now test, that the buffer
@@ -2299,7 +2313,7 @@ func! Test_normal46_ignore()
   bw!
 endfunc
 
-func! Test_normal47_visual_buf_wipe()
+func Test_normal47_visual_buf_wipe()
   " This was causing a crash or ml_get error.
   enew!
   call setline(1,'xxx')
@@ -2313,7 +2327,7 @@ func! Test_normal47_visual_buf_wipe()
   set nomodified
 endfunc
 
-func! Test_normal47_autocmd()
+func Test_normal47_autocmd()
   " disabled, does not seem to be possible currently
   throw "Skipped: not possible to test cursorhold autocmd while waiting for input in normal_cmd"
   new
@@ -2331,14 +2345,14 @@ func! Test_normal47_autocmd()
   bw!
 endfunc
 
-func! Test_normal48_wincmd()
+func Test_normal48_wincmd()
   new
   exe "norm! \<c-w>c"
   call assert_equal(1, winnr('$'))
   call assert_fails(":norm! \<c-w>c", "E444")
 endfunc
 
-func! Test_normal49_counts()
+func Test_normal49_counts()
   new
   call setline(1, 'one two three four five six seven eight nine ten')
   1
@@ -2347,7 +2361,7 @@ func! Test_normal49_counts()
   bw!
 endfunc
 
-func! Test_normal50_commandline()
+func Test_normal50_commandline()
   if !has("timers") || !has("cmdline_hist") || !has("vertsplit")
     return
   endif
@@ -2378,7 +2392,7 @@ func! Test_normal50_commandline()
   bw!
 endfunc
 
-func! Test_normal51_FileChangedRO()
+func Test_normal51_FileChangedRO()
   if !has("autocmd")
     return
   endif
@@ -2395,7 +2409,7 @@ func! Test_normal51_FileChangedRO()
   call delete("Xreadonly.log")
 endfunc
 
-func! Test_normal52_rl()
+func Test_normal52_rl()
   if !has("rightleft")
     return
   endif
@@ -2428,7 +2442,7 @@ func! Test_normal52_rl()
   bw!
 endfunc
 
-func! Test_normal53_digraph()
+func Test_normal53_digraph()
   if !has('digraphs')
     return
   endif
@@ -2516,6 +2530,29 @@ func Test_changelist()
   let &ul = save_ul
 endfunc
 
+func Test_nv_hat_count()
+  %bwipeout!
+  let l:nr = bufnr('%') + 1
+  call assert_fails(':execute "normal! ' . l:nr . '\<C-^>"', 'E92')
+
+  edit Xfoo
+  let l:foo_nr = bufnr('Xfoo')
+
+  edit Xbar
+  let l:bar_nr = bufnr('Xbar')
+
+  " Make sure we are not just using the alternate file.
+  edit Xbaz
+
+  call feedkeys(l:foo_nr . "\<C-^>", 'tx')
+  call assert_equal('Xfoo', fnamemodify(bufname('%'), ':t'))
+
+  call feedkeys(l:bar_nr . "\<C-^>", 'tx')
+  call assert_equal('Xbar', fnamemodify(bufname('%'), ':t'))
+
+  %bwipeout!
+endfunc
+
 func Test_delete_until_paragraph()
   new
   normal grádv}
diff --git a/src/nvim/testdir/test_window_cmd.vim b/src/nvim/testdir/test_window_cmd.vim
index c87c0a0af4..9f899fba04 100644
--- a/src/nvim/testdir/test_window_cmd.vim
+++ b/src/nvim/testdir/test_window_cmd.vim
@@ -117,15 +117,65 @@ func Test_window_vertical_split()
   bw
 endfunc
 
+" Test the ":wincmd ^" and "<C-W>^" commands.
 func Test_window_split_edit_alternate()
-  e Xa
-  e Xb
 
+  " Test for failure when the alternate buffer/file no longer exists.
+  edit Xfoo | %bw
+  call assert_fails(':wincmd ^', 'E23')
+
+  " Test for the expected behavior when we have two named buffers.
+  edit Xfoo | edit Xbar
   wincmd ^
-  call assert_equal('Xa', bufname(winbufnr(1)))
-  call assert_equal('Xb', bufname(winbufnr(2)))
+  call assert_equal('Xfoo', bufname(winbufnr(1)))
+  call assert_equal('Xbar', bufname(winbufnr(2)))
+  only
 
-  bw Xa Xb
+  " Test for the expected behavior when the alternate buffer is not named.
+  enew | let l:nr1 = bufnr('%')
+  edit Xfoo | let l:nr2 = bufnr('%')
+  wincmd ^
+  call assert_equal(l:nr1, winbufnr(1))
+  call assert_equal(l:nr2, winbufnr(2))
+  only
+
+  " Test the Normal mode command.
+  call feedkeys("\<C-W>\<C-^>", 'tx')
+  call assert_equal(l:nr2, winbufnr(1))
+  call assert_equal(l:nr1, winbufnr(2))
+
+  %bw!
+endfunc
+
+" Test the ":[count]wincmd ^" and "[count]<C-W>^" commands.
+func Test_window_split_edit_bufnr()
+
+  %bwipeout
+  let l:nr = bufnr('%') + 1
+  call assert_fails(':execute "normal! ' . l:nr . '\<C-W>\<C-^>"', 'E92')
+  call assert_fails(':' . l:nr . 'wincmd ^', 'E16')
+  call assert_fails(':0wincmd ^', 'E16')
+
+  edit Xfoo | edit Xbar | edit Xbaz
+  let l:foo_nr = bufnr('Xfoo')
+  let l:bar_nr = bufnr('Xbar')
+  let l:baz_nr = bufnr('Xbaz')
+
+  call feedkeys(l:foo_nr . "\<C-W>\<C-^>", 'tx')
+  call assert_equal('Xfoo', bufname(winbufnr(1)))
+  call assert_equal('Xbaz', bufname(winbufnr(2)))
+  only
+
+  call feedkeys(l:bar_nr . "\<C-W>\<C-^>", 'tx')
+  call assert_equal('Xbar', bufname(winbufnr(1)))
+  call assert_equal('Xfoo', bufname(winbufnr(2)))
+  only
+
+  execute l:baz_nr . 'wincmd ^'
+  call assert_equal('Xbaz', bufname(winbufnr(1)))
+  call assert_equal('Xbar', bufname(winbufnr(2)))
+
+  %bw!
 endfunc
 
 func Test_window_preview()
diff --git a/src/nvim/window.c b/src/nvim/window.c
index 1e6de73549..d7df048588 100644
--- a/src/nvim/window.c
+++ b/src/nvim/window.c
@@ -131,8 +131,20 @@ do_window (
   case '^':
     CHECK_CMDWIN;
     reset_VIsual_and_resel();  // stop Visual mode
-    cmd_with_count("split #", (char_u *)cbuf, sizeof(cbuf), Prenum);
-    do_cmdline_cmd(cbuf);
+
+    if (buflist_findnr(Prenum == 0 ? curwin->w_alt_fnum : Prenum) == NULL) {
+      if (Prenum == 0) {
+        EMSG(_(e_noalt));
+      } else {
+        EMSGN(_("E92: Buffer %" PRId64 " not found"), Prenum);
+      }
+      break;
+    }
+
+    if (!curbuf_locked() && win_split(0, 0) == OK) {
+      (void)buflist_getfile(Prenum == 0 ? curwin->w_alt_fnum : Prenum,
+                            (linenr_T)0, GETF_ALT, false);
+    }
     break;
 
   /* open new window */