From: glepnir <glephunter@gmail.com>
Date: Sat, 13 Jun 2026 19:32:44 +0000 (+0000)
Subject: patch 9.2.0639: gq with 'formatprg' fails on an empty buffer
X-Git-Tag: v9.2.0639^0
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=aefbca2977653a96f11061da80d6b72587497fb7;p=thirdparty%2Fvim.git

patch 9.2.0639: gq with 'formatprg' fails on an empty buffer

Problem:  gq (and other filters) on an empty buffer fail with
          "E20: Mark not set": when the filter produces no output,
          do_filter() still subtracts the line count from '[ and '],
          pushing '] to line 0.
Solution: when the filter produces no output, put '[ and '] on a valid
          line instead of subtracting past line 1 (glepnir).

related: neovim/neovim#30593
closes:  #19061

Signed-off-by: glepnir <glephunter@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
---

diff --git a/src/ex_cmds.c b/src/ex_cmds.c
index b2fc85c99e..803a10a2d7 100644
--- a/src/ex_cmds.c
+++ b/src/ex_cmds.c
@@ -1516,8 +1516,18 @@ do_filter(
 	     */
 	    curwin->w_cursor.lnum = line1;
 	    del_lines(linecount, TRUE);
-	    curbuf->b_op_start.lnum -= linecount;	// adjust '[
-	    curbuf->b_op_end.lnum -= linecount;		// adjust ']
+	    if (read_linecount == 0)
+	    {
+		// no filter output: clamp '[ and '] to a valid line
+		curbuf->b_op_start.lnum = curbuf->b_op_end.lnum =
+					MIN(line1, curbuf->b_ml.ml_line_count);
+		curbuf->b_op_start.col = curbuf->b_op_end.col = 0;
+	    }
+	    else
+	    {
+		curbuf->b_op_start.lnum -= linecount;	// adjust '[
+		curbuf->b_op_end.lnum -= linecount;	// adjust ']
+	    }
 	    write_lnum_adjust(-linecount);		// adjust last line
 							// for next write
 #ifdef FEAT_FOLDING
diff --git a/src/testdir/test_marks.vim b/src/testdir/test_marks.vim
index 61bfade627..d4b01dfda3 100644
--- a/src/testdir/test_marks.vim
+++ b/src/testdir/test_marks.vim
@@ -329,5 +329,26 @@ func Test_jump_mark_autocmd()
   bwipe!
 endfunc
 
+func Test_mark_formatprg_on_empty()
+  new
+  if has('win32')
+    setl formatprg=more
+  else
+    setl formatprg=cat
+  endif
+  call assert_equal([0, 0], [line("'["), col("'[")])
+  call assert_equal([0, 0], [line("']"), col("']")])
+  let v:errmsg = ''
+  try
+    norm! gqG
+  catch
+    call assert_report('gqG on empty buffer should not fail: ' .. v:exception)
+  endtry
+  call assert_true(empty(v:errmsg))
+  " col() is 1-based, so 1 == first column (:marks shows it as 0)
+  call assert_equal([1, 1], [line("'["), col("'[")])
+  call assert_equal([1, 1], [line("']"), col("']")])
+  bwipe!
+endfunc
 
 " vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/version.c b/src/version.c
index d4d8e477fa..1fdf8d1b01 100644
--- a/src/version.c
+++ b/src/version.c
@@ -759,6 +759,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    639,
 /**/
     638,
 /**/