patch 8.2.4942: error when setting 'filetype' in help file againv8.2.4942

Problem:    Error when setting 'filetype' in help file again.
Solution:   Deal with text property type already existing. (closes #10409)

1 files changed, 11 insertions, 5 deletions

diff --git a/runtime/import/dist/vimhelp.vim b/runtime/import/dist/vimhelp.vim
index 1f587251b9..00cc79cfdb 100644
--- a/runtime/import/dist/vimhelp.vim
+++ b/runtime/import/dist/vimhelp.vim
@@ -9,11 +9,17 @@ export def HighlightGroups()
   while getline(lnum) !~ '===' && lnum < line('$')
     var word: string = getline(lnum)->matchstr('^\w\+\ze\t')
     if word->hlexists()
-      prop_type_add('help-hl-' .. word, {
-	bufnr: buf,
-	highlight: word,
-	combine: false,
-	})
+      var name = 'help-hl-' .. word
+      if prop_type_list({bufnr: buf})->match(name) == -1
+	prop_type_add('help-hl-' .. word, {
+	  bufnr: buf,
+	  highlight: word,
+	  combine: false,
+	  })
+      else
+	# was called before, delete existing properties
+	prop_remove({type: name, bufnr: buf})
+      endif
       prop_add(lnum, 1, {length: word->strlen(), type: 'help-hl-' .. word})
     endif
     ++lnum