vim-patch:9.1.0334: No test for highlight behavior with 'ambiwidth' (#28354)

Problem:  No test for highlight behavior with 'ambiwidth'.
Solution: Add a screendump test for 'ambiwidth' with 'cursorline'.
          (zeertzjq)

closes: vim/vim#14554

a59e031aa0

test/old/testdir/test_regexp_utf8.vim

@@ -372,7 +372,7 @@ func Test_multibyte_chars()
 endfunc
 
 " check that 'ambiwidth' does not change the meaning of \p
-func Test_ambiwidth()
+func Test_regexp_ambiwidth()
   set regexpengine=1 ambiwidth=single
   call assert_equal(0, match("\u00EC", '\p'))
   set regexpengine=1 ambiwidth=double

test/old/testdir/test_utf8.vim

@@ -62,6 +62,9 @@ func Test_customlist_completion()
   call assert_equal('"Test3 N', getreg(':'))
 
   call garbagecollect(1)
+  delcommand Test1
+  delcommand Test2
+  delcommand Test3
 endfunc
 
 " Yank one 3 byte character and check the mark columns.
@@ -297,6 +300,40 @@ func Test_setcellwidths_dump()
   call StopVimInTerminal(buf)
 endfunc
 
+" For some reason this test causes Test_customlist_completion() to fail on CI,
+" so run it as the last test.
+func Test_zz_ambiwidth_hl_dump()
+  CheckRunVimInTerminal
+
+  let lines =<< trim END
+      call setline(1, [repeat("\u2103", 60), repeat("\u2103", 60)])
+      set ambiwidth=single cursorline list display=lastline
+  END
+  call writefile(lines, 'XAmbiwidthHl', 'D')
+  let buf = RunVimInTerminal('-S XAmbiwidthHl', {'rows': 6, 'cols': 50})
+  call VerifyScreenDump(buf, 'Test_ambiwidth_hl_dump_1', {})
+
+  call term_sendkeys(buf, ":set ambiwidth=double\<CR>")
+  call term_sendkeys(buf, ":echo\<CR>")
+  call VerifyScreenDump(buf, 'Test_ambiwidth_hl_dump_2', {})
+
+  call term_sendkeys(buf, ":set ambiwidth=single\<CR>")
+  call term_sendkeys(buf, ":echo\<CR>")
+  call VerifyScreenDump(buf, 'Test_ambiwidth_hl_dump_1', {})
+
+  if 0 " Enable after #14539 is fixed
+  call term_sendkeys(buf, ":call setcellwidths([[0x2103, 0x2103, 2]])\<CR>")
+  call term_sendkeys(buf, ":echo\<CR>")
+  call VerifyScreenDump(buf, 'Test_ambiwidth_hl_dump_2', {})
+
+  call term_sendkeys(buf, ":call setcellwidths([[0x2103, 0x2103, 1]])\<CR>")
+  call term_sendkeys(buf, ":echo\<CR>")
+  call VerifyScreenDump(buf, 'Test_ambiwidth_hl_dump_1', {})
+  endif
+
+  call StopVimInTerminal(buf)
+endfunc
+
 func Test_print_overlong()
   " Text with more composing characters than MB_MAXBYTES.
   new