vim-patch:9.0.0175: spell checking for capital not working with trailing space

Problem:    Spell checking for capital not working with trailing space.
Solution:   Do not calculate cap_col at the end of the line. (Christian
            Brabandt, closes vim/vim#10870, issue vim/vim#10838)

https://github.com/vim/vim/commit/afa23d1b99692e3c726eb694933ab348b442a1e4

Co-authored-by: Christian Brabandt <cb@256bit.org>

3 files changed, 84 insertions, 33 deletions

diff --git a/src/nvim/drawline.c b/src/nvim/drawline.c
index 927b1247be..a49b2ac6d6 100644
--- a/src/nvim/drawline.c
+++ b/src/nvim/drawline.c
@@ -2188,12 +2188,13 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool nochange,
         v = (ptr - line);
         if (has_spell && v >= word_end && v > cur_checked_col) {
           spell_attr = 0;
-          if (c != 0 && ((!has_syntax && !no_plain_buffer) || can_spell)) {
-            char *prev_ptr;
+          char *prev_ptr = ptr - mb_l;
+          // do not calculate cap_col at the end of the line or when
+          // only white space is following
+          if (c != 0 && (*skipwhite(prev_ptr) != NUL)
+              && ((!has_syntax && !no_plain_buffer) || can_spell)) {
             char *p;
-            int len;
             hlf_T spell_hlf = HLF_COUNT;
-            prev_ptr = ptr - mb_l;
             v -= mb_l - 1;
 
             // Use nextline[] if possible, it has the start of the
@@ -2206,7 +2207,7 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool nochange,
             cap_col -= (int)(prev_ptr - line);
             size_t tmplen = spell_check(wp, p, &spell_hlf, &cap_col, nochange);
             assert(tmplen <= INT_MAX);
-            len = (int)tmplen;
+            int len = (int)tmplen;
             word_end = (int)v + len;
 
             // In Insert mode only highlight a word that
diff --git a/test/functional/ui/spell_spec.lua b/test/functional/ui/spell_spec.lua
index 0f553d4a9b..c5c4ec3b99 100644
--- a/test/functional/ui/spell_spec.lua
+++ b/test/functional/ui/spell_spec.lua
@@ -3,9 +3,9 @@
 local helpers = require('test.functional.helpers')(after_each)
 local Screen = require('test.functional.ui.screen')
 local clear = helpers.clear
+local exec = helpers.exec
 local feed = helpers.feed
 local insert = helpers.insert
-local command = helpers.command
 local meths = helpers.meths
 local curbufmeths = helpers.curbufmeths
 local is_os = helpers.is_os
@@ -32,7 +32,7 @@ describe("'spell'", function()
 
   it('joins long lines #7937', function()
     if is_os('openbsd') then pending('FIXME #12104', function() end) return end
-    command('set spell')
+    exec('set spell')
     insert([[
     Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod
     tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam,
@@ -57,31 +57,58 @@ describe("'spell'", function()
 
   -- oldtest: Test_spell_screendump()
   it('has correct highlight at start of line', function()
-    insert([[
-    "This is some text without any spell errors.  Everything",
-    "should just be black, nothing wrong here.",
-    "",
-    "This line has a sepll error. and missing caps.",
-    "And and this is the the duplication.",
-    "with missing caps here.",
+    exec([=[
+      call setline(1, [
+        \"This is some text without any spell errors.  Everything",
+        \"should just be black, nothing wrong here.",
+        \"",
+        \"This line has a sepll error. and missing caps.",
+        \"And and this is the the duplication.",
+        \"with missing caps here.",
+      \])
+      set spell spelllang=en_nz
+    ]=])
+    screen:expect([[
+      ^This is some text without any spell errors.  Everything                         |
+      should just be black, nothing wrong here.                                       |
+                                                                                      |
+      This line has a {1:sepll} error. {2:and} missing caps.                                  |
+      {1:And and} this is {1:the the} duplication.                                            |
+      {2:with} missing caps here.                                                         |
+      {0:~                                                                               }|
+                                                                                      |
     ]])
-    command('set spell spelllang=en_nz')
+  end)
+
+  -- oldtest: Test_spell_screendump_spellcap()
+  it('has correct highlight at start of line with trailing space', function()
+    exec([=[
+      call setline(1, [
+        \"   This line has a sepll error. and missing caps and trailing spaces.   ",
+        \"another missing cap here.",
+        \"",
+        \"and here.",
+        \"    ",
+        \"and here."
+      \])
+      set spell spelllang=en
+    ]=])
     screen:expect([[
-    "This is some text without any spell errors.  Everything",                      |
-    "should just be black, nothing wrong here.",                                    |
-    "",                                                                             |
-    "This line has a {1:sepll} error. {2:and} missing caps.",                               |
-    "{1:And and} this is {1:the the} duplication.",                                         |
-    "with missing caps here.",                                                      |
-    ^                                                                                |
-                                                                                    |
+      ^   This line has a {1:sepll} error. {2:and} missing caps and trailing spaces.           |
+      {2:another} missing cap here.                                                       |
+                                                                                      |
+      {2:and} here.                                                                       |
+                                                                                      |
+      {2:and} here.                                                                       |
+      {0:~                                                                               }|
+                                                                                      |
     ]])
   end)
 
   it('extmarks, "noplainbuffer" and syntax #20385 #23398', function()
-    command('set filetype=c')
-    command('syntax on')
-    command('set spell')
+    exec('set filetype=c')
+    exec('syntax on')
+    exec('set spell')
     insert([[
       #include <stdbool.h>
       bool func(void);
@@ -119,7 +146,7 @@ describe("'spell'", function()
       {0:~                                                                               }|
       {6:search hit BOTTOM, continuing at TOP}                                            |
     ]])
-    command('echo ""')
+    exec('echo ""')
     local ns = meths.create_namespace("spell")
     -- extmark with spell=true enables spell
     local id = curbufmeths.set_extmark(ns, 1, 4, { end_row = 1, end_col = 10, spell = true })
@@ -168,7 +195,7 @@ describe("'spell'", function()
       {0:~                                                                               }|
       {6:search hit TOP, continuing at BOTTOM}                                            |
     ]])
-    command('echo ""')
+    exec('echo ""')
     curbufmeths.del_extmark(ns, id)
     screen:expect([[
       {3:#include }{4:<stdbool.h>}                                                            |
@@ -192,7 +219,7 @@ describe("'spell'", function()
                                                                                       |
     ]])
     -- "noplainbuffer" shouldn't change spellchecking behavior with syntax enabled
-    command('set spelloptions+=noplainbuffer')
+    exec('set spelloptions+=noplainbuffer')
     screen:expect_unchanged()
     feed('[s')
     screen:expect([[
@@ -206,7 +233,7 @@ describe("'spell'", function()
                                                                                       |
     ]])
     -- no spellchecking with "noplainbuffer" and syntax disabled
-    command('syntax off')
+    exec('syntax off')
     screen:expect([[
       #include <stdbool.h>                                                            |
       bool func(void);                                                                |
@@ -228,9 +255,9 @@ describe("'spell'", function()
       {0:~                                                                               }|
       {6:search hit BOTTOM, continuing at TOP}                                            |
     ]])
-    command('echo ""')
+    exec('echo ""')
     -- everything is spellchecked without "noplainbuffer" with syntax disabled
-    command('set spelloptions&')
+    exec('set spelloptions&')
     screen:expect([[
       #include <{1:stdbool}.h>                                                            |
       {1:bool} {1:func}(void);                                                                |
@@ -256,7 +283,7 @@ describe("'spell'", function()
 
   it('and syntax does not clear extmark highlighting at the start of a word', function()
     screen:try_resize(43, 3)
-    command([[
+    exec([[
       set spell
       syntax match Constant "^.*$"
       call setline(1, "This is some text without any spell errors.")
diff --git a/test/old/testdir/test_spell.vim b/test/old/testdir/test_spell.vim
index c840e834b9..1d122d7726 100644
--- a/test/old/testdir/test_spell.vim
+++ b/test/old/testdir/test_spell.vim
@@ -996,6 +996,29 @@ func Test_spell_screendump()
   call delete('XtestSpell')
 endfunc
 
+func Test_spell_screendump_spellcap()
+  CheckScreendump
+
+  let lines =<< trim END
+       call setline(1, [
+             \ "   This line has a sepll error. and missing caps and trailing spaces.   ",
+             \ "another missing cap here.",
+             \ "",
+             \ "and here.",
+             \ "    ",
+             \ "and here."
+             \ ])
+       set spell spelllang=en
+  END
+  call writefile(lines, 'XtestSpellCap')
+  let buf = RunVimInTerminal('-S XtestSpellCap', {'rows': 8})
+  call VerifyScreenDump(buf, 'Test_spell_2', {})
+
+  " clean up
+  call StopVimInTerminal(buf)
+  call delete('XtestSpellCap')
+endfunc
+
 let g:test_data_aff1 = [
       \"SET ISO8859-1",
       \"TRY esianrtolcdugmphbyfvkwjkqxz-\xEB\xE9\xE8\xEA\xEF\xEE\xE4\xE0\xE2\xF6\xFC\xFB'ESIANRTOLCDUGMPHBYFVKWJKQXZ",