patch 8.2.2068: transparent syntax item uses start/end of containing region

Problem:    Transparent syntax item uses start/end of containing region.
Solution:   Do not change the startpos and endpos of a transparent region to
            that of its containing region. (Adrian Ghizaru, closes #7349,
            closes #7391)

src/syntax.c

@@ -2606,8 +2606,6 @@ update_si_attr(int idx)
 	{
 	    sip->si_attr = CUR_STATE(idx - 1).si_attr;
 	    sip->si_trans_id = CUR_STATE(idx - 1).si_trans_id;
-	    sip->si_h_startpos = CUR_STATE(idx - 1).si_h_startpos;
-	    sip->si_h_endpos = CUR_STATE(idx - 1).si_h_endpos;
 	    if (sip->si_cont_list == NULL)
 	    {
 		sip->si_flags |= HL_TRANS_CONT;

src/testdir/test_syntax.vim

@@ -27,6 +27,26 @@ func GetSyntaxItem(pat)
   return c
 endfunc
 
+func AssertHighlightGroups(lnum, startcol, expected, trans = 1, msg = "")
+  " Assert that the characters starting at a given (line, col)
+  " sequentially match the expected highlight groups.
+  " If groups are provided as a string, each character is assumed to be a
+  " group and spaces represent no group, useful for visually describing tests.
+  let l:expectedGroups = type(a:expected) == v:t_string
+        \ ? a:expected->split('\zs')->map({_, v -> trim(v)})
+        \ : a:expected
+  let l:errors = 0
+  let l:msg = (a:msg->empty() ? "" : a:msg .. ": ")
+        \ .. "Wrong highlight group at " .. a:lnum .. ","
+
+  for l:i in range(a:startcol, a:startcol + l:expectedGroups->len() - 1)
+    let l:errors += synID(a:lnum, l:i, a:trans)
+          \ ->synIDattr("name")
+          \ ->assert_equal(l:expectedGroups[l:i - 1],
+          \    l:msg .. l:i)
+  endfor
+endfunc
+
 func Test_syn_iskeyword()
   new
   call setline(1, [
@@ -824,4 +844,80 @@ func Test_search_syntax_skip()
   bwipe!
 endfunc
 
+func Test_syn_contained_transparent()
+  " Comments starting with "Regression:" show the result when the highlighting
+  " span of the containing item is assigned to the contained region.
+  syntax on
+
+  let l:case = "Transparent region contained in region"
+  new
+  syntax region X start=/\[/ end=/\]/ contained transparent
+  syntax region Y start=/(/ end=/)/ contains=X
+
+  call setline(1,  "==(--[~~]--)==")
+  let l:expected = "  YYYYYYYYYY  "
+  eval AssertHighlightGroups(1, 1, l:expected, 1, l:case)
+  syntax clear Y X
+  bw!
+
+  let l:case = "Transparent region extends region"
+  new
+  syntax region X start=/\[/ end=/\]/ contained transparent
+  syntax region Y start=/(/ end=/)/ end=/e/ contains=X
+
+  call setline(1,  "==(--[~~e~~]--)==")
+  let l:expected = "  YYYYYYYYYYYYY  "
+  " Regression:    "  YYYYYYY   YYY  "
+  eval AssertHighlightGroups(1, 1, l:expected, 1, l:case)
+  syntax clear Y X
+  bw!
+
+  let l:case = "Nested transparent regions extend region"
+  new
+  syntax region X start=/\[/ end=/\]/ contained transparent
+  syntax region Y start=/(/ end=/)/ end=/e/ contains=X
+
+  call setline(1,  "==(--[~~e~~[~~e~~]~~e~~]--)==")
+  let l:expected = "  YYYYYYYYYYYYYYYYYYYYYYYYY  "
+  " Regression:    "  YYYYYYY         YYYYYYYYY  "
+  eval AssertHighlightGroups(1, 1, l:expected, 1, l:case)
+  syntax clear Y X
+  bw!
+
+  let l:case = "Transparent region contained in match"
+  new
+  syntax region X start=/\[/ end=/\]/ contained transparent
+  syntax match Y /(.\{-})/ contains=X
+
+  call setline(1,  "==(--[~~]--)==")
+  let l:expected = "  YYYYYYYYYY  "
+  eval AssertHighlightGroups(1, 1, l:expected, 1, l:case)
+  syntax clear Y X
+  bw!
+
+  let l:case = "Transparent region extends match"
+  new
+  syntax region X start=/\[/ end=/\]/ contained transparent
+  syntax match Y /(.\{-}[e)]/ contains=X
+
+  call setline(1,  "==(--[~~e~~]--)==")
+  let l:expected = "  YYYYYYYYYY     "
+  " Regression:    "  YYYYYYY        "
+  eval AssertHighlightGroups(1, 1, l:expected, 1, l:case)
+  syntax clear Y X
+  bw!
+
+  let l:case = "Nested transparent regions extend match"
+  new
+  syntax region X start=/\[/ end=/\]/ contained transparent
+  syntax match Y /(.\{-}[e)]/ contains=X
+
+  call setline(1,  "==(--[~~e~~[~~e~~]~~e~~]--)==")
+  let l:expected = "  YYYYYYYYYYYYYYYYYYYYYY     "
+  " Regression:    "  YYYYYYY         YYYYYY     "
+  eval AssertHighlightGroups(1, 1, l:expected, 1, l:case)
+  syntax clear Y X
+  bw!
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2068,
 /**/
     2067,
 /**/