Commit: patch 9.2.0124: auto-format may swallow white space

[Christian Brabandt]

patch 9.2.0124: auto-format may swallow white space

Commit: https://github.com/vim/vim/commit/24fd6980457a942d58c2fe74b945d951081bf8ab
Author: Daniel Müller <de...@posteo.net>
Date: Sun Mar 8 20:24:10 2026 +0000

patch 9.2.0124: auto-format may swallow white space

Problem: With auto paragraph formatting enabled, when a user makes an
attempt to add a new word before the end of a line and with
the following space bringing the line width over 'textwidth',
the space ends up just getting swallowed by the editor.
Solution: Detect such a constellation and do not auto-format in that
case (Daniel Müller).

closes: #19593

Signed-off-by: Daniel Müller <de...@posteo.net>
Signed-off-by: Christian Brabandt <c...@256bit.org>

diff --git a/src/testdir/test_textformat.vim b/src/testdir/test_textformat.vim
index f4dedfacb..91fe943c1 100644
--- a/src/testdir/test_textformat.vim
+++ b/src/testdir/test_textformat.vim
@@ -1155,6 +1155,32 @@ func Test_fo_a_w()
%bw!
endfunc

+" Test that auto-format ('a' flag) preserves spaces typed in the middle of a line
+func Test_fo_a_midline_space()
+ new
+ let lines = [
+ \ 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa it but',
+ \ 'Lorem Ipsum is simply dummy text of the printing and typesetting dasddd',
+ \ 'industry.',
+ \ ]
+ call setline(1, lines)
+ set fo=ta tw=70
+
+ " Prevent INPUT_BUFLEN batching so auto_format runs between keystrokes
+ autocmd InsertCharPre * " nothing
+
+ " Position at 't' of 'it' (col 68) and type space then Z
+ call cursor(1, 68)
+ call feedkeys("a Z\<Esc>", 'xt')
+
+ " The space between 'it' and 'Z' must be preserved
+ call assert_match('it Z', getline(1))
+
+ autocmd! InsertCharPre
+ set fo& tw&
+ bw!
+endfunc
+
" Test for formatting lines using gq in visual mode
func Test_visual_gq_format()
new
diff --git a/src/textformat.c b/src/textformat.c
index 8f4f2dd08..024c80b68 100644
--- a/src/textformat.c
+++ b/src/textformat.c
@@ -703,6 +703,24 @@ auto_format(
curwin->w_cursor = pos;
}

+ // Also skip formatting when the user just typed whitespace in the
+ // middle of the line. Reformatting would join all paragraph lines and
+ // re-wrap, consuming the space at the line break point via
+ // OPENLINE_DELSPACES. By deferring, the next non-whitespace character
+ // will be inserted adjacent to the space, keeping it protected from
+ // being consumed at a line break. auto_format() will then reformat
+ // properly on the next keystroke.
+ if (*old != NUL && !trailblank && !wasatend && pos.col > 0
+ && (State & MODE_INSERT))
+ {
+ char_u *line = ml_get_curline();
+ if (WHITECHAR(line[pos.col - 1]))
+ {
+ curwin->w_cursor = pos;
+ return;
+ }
+ }
+
// With the 'c' flag in 'formatoptions' and 't' missing: only format
// comments.
if (has_format_option(FO_WRAP_COMS) && !has_format_option(FO_WRAP)
diff --git a/src/version.c b/src/version.c
index 446c47fe0..5b78d544e 100644
--- a/src/version.c
+++ b/src/version.c
@@ -734,6 +734,8 @@ static char *(features[]) =

static int included_patches[] =
{ /* Add new patch number below this line */
+/**/
+ 124,
/**/
123,
/**/