vim-patch:9.1.1831: stray vseps in right-most 'winfixwidth' window

Problem:  vertical separator of 'winfixwidth' windows may remain if they
          become right-most windows from closing windows to the right.
Solution: Don't implicitly rely on frame_new_width to fix vseps, as the
          call may be skipped for 'winfixwidth' windows to preserve
          their width; do it explicitly in winframe_remove (Sean Dewar).

Note that I prefer win_new_width here over setting w_width directly, which
would've previously been done by win_split_ins after frame_add_vsep, as this
wasn't true for winframe_remove.

Though the equivalent issue of bottom 'winfixheight' windows leaving stray
statuslines with &ls=0 doesn't seem to exist, test it anyway.

closes: vim/vim#18481

620c655677

Nvim: calling win_new_width over setting w_width directly is especially
important in making sure stuff like w_view_width is correct here.

Co-authored-by: Sean Dewar <6256228+seandewar@users.noreply.github.com>
(cherry picked from commit 7923e847ca)

test/functional/legacy/window_cmd_spec.lua

@@ -1,11 +1,14 @@
+local t = require('test.testutil')
 local n = require('test.functional.testnvim')()
 local Screen = require('test.functional.ui.screen')
 
 local clear = n.clear
+local eq = t.eq
 local exec = n.exec
 local exec_lua = n.exec_lua
 local command = n.command
 local feed = n.feed
+local fn = n.fn
 
 -- oldtest: Test_window_cmd_ls0_split_scrolling()
 it('scrolling with laststatus=0 and :botright split', function()
@@ -354,3 +357,53 @@ describe('splitkeep', function()
     ]])
   end)
 end)
+
+-- oldtest: Test_winfixsize_vsep_statusline()
+it("'winfixwidth/height' does not leave stray vseps/statuslines", function()
+  clear()
+  local screen = Screen.new(75, 8)
+  exec([[
+    set noequalalways splitbelow splitright
+    vsplit
+    setlocal winfixwidth
+    vsplit
+  ]])
+  eq(16, fn.winwidth(1))
+  eq(37, fn.winwidth(2))
+  eq(20, fn.winwidth(3))
+
+  command('quit')
+  screen:expect([[
+    ^                                    │                                      |
+    {1:~                                   }│{1:~                                     }|*5
+    {3:[No Name]                            }{2:[No Name]                             }|
+                                                                               |
+  ]])
+  -- Checks w_view_width in Nvim; especially important as the screen test may still pass if only
+  -- w_width changed to make room for the vsep.
+  eq(36, fn.winwidth(1))
+  eq(38, fn.winwidth(2))
+
+  exec([[
+    set laststatus=0
+    only
+    split
+    set winfixheight
+    split
+  ]])
+  eq(1, fn.winheight(1))
+  eq(3, fn.winheight(2))
+  eq(1, fn.winheight(3))
+
+  command('quit')
+  screen:expect([[
+    ^                                                                           |
+    {1:~                                                                          }|
+    {3:[No Name]                                                                  }|
+                                                                               |
+    {1:~                                                                          }|*3
+                                                                               |
+  ]])
+  eq(2, fn.winheight(1))
+  eq(4, fn.winheight(2))
+end)

test/old/testdir/test_window_cmd.vim

@@ -2261,4 +2261,50 @@ func Test_winfixsize_positions()
   %bwipe
 endfunc
 
+func Test_winfixsize_vsep_statusline()
+  CheckScreendump
+  let lines =<< trim END
+    set noequalalways splitbelow splitright
+    vsplit
+    setlocal winfixwidth
+    vsplit
+    func SetupWfh()
+      set laststatus=0
+      only
+      split
+      set winfixheight
+      split
+    endfunc
+  END
+  call writefile(lines, 'XTestWinfixsizeVsepStatusline', 'D')
+  let buf = RunVimInTerminal('-S XTestWinfixsizeVsepStatusline', #{rows: 8})
+
+  call term_sendkeys(buf, ":echo winwidth(1) winwidth(2) winwidth(3)\n")
+  call WaitForAssert({-> assert_match('^16 37 20\>', term_getline(buf, 8))})
+
+  call term_sendkeys(buf, ":quit\n")
+  call VerifyScreenDump(buf, 'Test_winfixsize_vsep_statusline_1', {})
+
+  " Reported widths should be consistent with the screen dump.
+  call term_sendkeys(buf, ":echo winwidth(1) winwidth(2)\n")
+  " (May be better if 'wfw' window remains at 37 columns, but the resize is
+  " consistent with how things currently work for 'winfix*' windows)
+  call WaitForAssert({-> assert_match('^36 38\>', term_getline(buf, 8))})
+
+  " For good measure, also check bottom-most 'winfixheight' windows don't leave
+  " stray statuslines with &laststatus=0.
+  call term_sendkeys(buf,
+        \ ":call SetupWfh() | echo winheight(1) winheight(2) winheight(3)\n")
+  call WaitForAssert({-> assert_match('^1 3 1\>', term_getline(buf, 8))})
+
+  call term_sendkeys(buf, ":quit\n")
+  call VerifyScreenDump(buf, 'Test_winfixsize_vsep_statusline_2', {})
+
+  call term_sendkeys(buf, ":echo winheight(1) winheight(2)\n")
+  " (Likewise, may be better if 'wfh' window remains at 3 rows)
+  call WaitForAssert({-> assert_match('^2 4\>', term_getline(buf, 8))})
+
+  call StopVimInTerminal(buf)
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab