vim-patch:8.2.1705: "verbose hi Name" reports incorrect info after ":hi clear"

Problem:    "verbose hi Name" reports incorrect info after ":hi clear".
Solution:   Store the script context. (Antony Scriven, closes vim/vim#6975)
https://github.com/vim/vim/commit/e8df0104985af58ee501a6fbac8ac9f886e84e5a

Also adds src/nvim/testdir/script_util.vim which originates from patch 8.2.1366
(https://github.com/vim/vim/commit/a6296200bd5191bab7efcdcc16c9e79eb498e8e0)
because some tests in test_highlight.vim use it for testing :verbose.
Should merge this and older related patches later.

Also, fix collateral damage to test_options.vim

test_options tests for file name completion in the test directory, but
since we've added a new file, the test output is now different.  This
test is slightly different from upstream anyway, so for now we just add
the file name.  This may change when more upstream patches are added
which alter this test.

4 files changed, 111 insertions, 8 deletions

diff --git a/src/nvim/syntax.c b/src/nvim/syntax.c
index 9501093e21..d204968c0f 100644
--- a/src/nvim/syntax.c
+++ b/src/nvim/syntax.c
@@ -61,6 +61,7 @@ struct hl_group {
   int sg_link;                  ///< link to this highlight group ID
   int sg_deflink;               ///< default link; restored in highlight_clear()
   int sg_set;                   ///< combination of flags in \ref SG_SET
+  sctx_T sg_deflink_sctx;       ///< script where the default link was set
   sctx_T sg_script_ctx;         ///< script in which the group was last set
   // for terminal UIs
   int sg_cterm;                 ///< "cterm=" highlighting attr
@@ -6633,6 +6634,8 @@ void do_highlight(const char *line, const bool forceit, const bool init)
       hlgroup = &HL_TABLE()[from_id - 1];
       if (dodefault && (forceit || hlgroup->sg_deflink == 0)) {
         hlgroup->sg_deflink = to_id;
+        hlgroup->sg_deflink_sctx = current_sctx;
+        hlgroup->sg_deflink_sctx.sc_lnum += sourcing_lnum;
       }
     }
 
@@ -7114,14 +7117,11 @@ static void highlight_clear(int idx)
   XFREE_CLEAR(HL_TABLE()[idx].sg_rgb_bg_name);
   XFREE_CLEAR(HL_TABLE()[idx].sg_rgb_sp_name);
   HL_TABLE()[idx].sg_blend = -1;
-  // Restore any default link.
+  // Restore default link and context if they exist. Otherwise clears.
   HL_TABLE()[idx].sg_link = HL_TABLE()[idx].sg_deflink;
-  // Clear the script ID only when there is no link, since that is not
-  // cleared.
-  if (HL_TABLE()[idx].sg_link == 0) {
-    HL_TABLE()[idx].sg_script_ctx.sc_sid = 0;
-    HL_TABLE()[idx].sg_script_ctx.sc_lnum = 0;
-  }
+  // Since we set the default link, set the location to where the default
+  // link was set.
+  HL_TABLE()[idx].sg_script_ctx = HL_TABLE()[idx].sg_deflink_sctx;
 }
 
 
diff --git a/src/nvim/testdir/script_util.vim b/src/nvim/testdir/script_util.vim
new file mode 100644
index 0000000000..9913b1dfaf
--- /dev/null
+++ b/src/nvim/testdir/script_util.vim
@@ -0,0 +1,69 @@
+" Functions shared by the tests for Vim Script
+
+" Commands to track the execution path of a script
+com!		   XpathINIT  let g:Xpath = ''
+com! -nargs=1 -bar Xpath      let g:Xpath ..= <args>
+com!               XloopINIT  let g:Xloop = 1
+com! -nargs=1 -bar Xloop      let g:Xpath ..= <args> .. g:Xloop
+com!               XloopNEXT  let g:Xloop += 1
+
+" MakeScript() - Make a script file from a function.			    {{{2
+"
+" Create a script that consists of the body of the function a:funcname.
+" Replace any ":return" by a ":finish", any argument variable by a global
+" variable, and every ":call" by a ":source" for the next following argument
+" in the variable argument list.  This function is useful if similar tests are
+" to be made for a ":return" from a function call or a ":finish" in a script
+" file.
+func MakeScript(funcname, ...)
+    let script = tempname()
+    execute "redir! >" . script
+    execute "function" a:funcname
+    redir END
+    execute "edit" script
+    " Delete the "function" and the "endfunction" lines.  Do not include the
+    " word "function" in the pattern since it might be translated if LANG is
+    " set.  When MakeScript() is being debugged, this deletes also the debugging
+    " output of its line 3 and 4.
+    exec '1,/.*' . a:funcname . '(.*)/d'
+    /^\d*\s*endfunction\>/,$d
+    %s/^\d*//e
+    %s/return/finish/e
+    %s/\<a:\(\h\w*\)/g:\1/ge
+    normal gg0
+    let cnt = 0
+    while search('\<call\s*\%(\u\|s:\)\w*\s*(.*)', 'W') > 0
+	let cnt = cnt + 1
+	s/\<call\s*\%(\u\|s:\)\w*\s*(.*)/\='source ' . a:{cnt}/
+    endwhile
+    g/^\s*$/d
+    write
+    bwipeout
+    return script
+endfunc
+
+" ExecAsScript - Source a temporary script made from a function.	    {{{2
+"
+" Make a temporary script file from the function a:funcname, ":source" it, and
+" delete it afterwards.  However, if an exception is thrown the file may remain,
+" the caller should call DeleteTheScript() afterwards.
+let s:script_name = ''
+function! ExecAsScript(funcname)
+    " Make a script from the function passed as argument.
+    let s:script_name = MakeScript(a:funcname)
+
+    " Source and delete the script.
+    exec "source" s:script_name
+    call delete(s:script_name)
+    let s:script_name = ''
+endfunction
+
+function! DeleteTheScript()
+    if s:script_name
+	call delete(s:script_name)
+	let s:script_name = ''
+    endif
+endfunc
+
+com! -nargs=1 -bar ExecAsScript call ExecAsScript(<f-args>)
+
diff --git a/src/nvim/testdir/test_highlight.vim b/src/nvim/testdir/test_highlight.vim
index e7ee42ecd6..ce22de09ca 100644
--- a/src/nvim/testdir/test_highlight.vim
+++ b/src/nvim/testdir/test_highlight.vim
@@ -3,6 +3,7 @@
 source view_util.vim
 source screendump.vim
 source check.vim
+source script_util.vim
 
 func Test_highlight()
   " basic test if ":highlight" doesn't crash
@@ -661,6 +662,39 @@ func Test_highlight_clear_restores_links()
   call assert_equal(HighlightArgs('aaa'), hl_aaa_ddd)
 endfunc
 
+func Test_highlight_clear_restores_context()
+  func FuncContextDefault()
+    hi def link Context ContextDefault
+  endfun
+
+  func FuncContextRelink()
+    " Dummy line
+    hi link Context ContextRelink
+  endfunc
+
+  let scriptContextDefault = MakeScript("FuncContextDefault")
+  let scriptContextRelink = MakeScript("FuncContextRelink")
+  let patContextDefault = fnamemodify(scriptContextDefault, ':t') .. ' line 1'
+  let patContextRelink = fnamemodify(scriptContextRelink, ':t') .. ' line 2'
+
+  exec "source" scriptContextDefault
+  let hlContextDefault = execute("verbose hi Context")
+  call assert_match(patContextDefault, hlContextDefault)
+
+  exec "source" scriptContextRelink
+  let hlContextRelink = execute("verbose hi Context")
+  call assert_match(patContextRelink, hlContextRelink)
+
+  hi clear
+  let hlContextAfterClear = execute("verbose hi Context")
+  call assert_match(patContextDefault, hlContextAfterClear)
+
+  delfunc FuncContextDefault
+  delfunc FuncContextRelink
+  call delete(scriptContextDefault)
+  call delete(scriptContextRelink)
+endfunc
+
 func Test_highlight_default_colorscheme_restores_links()
   hi link TestLink Identifier
   hi TestHi ctermbg=red
diff --git a/src/nvim/testdir/test_options.vim b/src/nvim/testdir/test_options.vim
index 1202b842fd..d23f0b5021 100644
--- a/src/nvim/testdir/test_options.vim
+++ b/src/nvim/testdir/test_options.vim
@@ -225,7 +225,7 @@ func Test_set_completion()
 
   " Expand files and directories.
   call feedkeys(":set tags=./\<C-A>\<C-B>\"\<CR>", 'tx')
-  call assert_match('./samples/ ./sautest/ ./screendump.vim ./setup.vim ./shared.vim', @:)
+  call assert_match('./samples/ ./sautest/ ./screendump.vim ./script_util.vim ./setup.vim ./shared.vim', @:)
 
   call feedkeys(":set tags=./\\\\ dif\<C-A>\<C-B>\"\<CR>", 'tx')
   call assert_equal('"set tags=./\\ diff diffexpr diffopt', @:)