fix(tui): don't overwrite an assertion faliure message on exit

If nvim exited with nonzero status this is for one of the two reasons
- `:cquit` was invoked. This is used by users and plugins to communicate
  a result, like a nonzero status will fail a `git commit` operation
- There was an internal error or deadly signal. in this case an error
  message was likely written to stderr or to the screen.

In the latter case, the error message was often hidden by the TUI
exiting altscreen mode, which erases all visible terminal text.

This change prevents this in the latter case, while still cleaning up
the terminal properly when `:cquit` was deliberatily invoked.
Other cleanup like exiting mouse mode and raw mode is still done.

1 files changed, 14 insertions, 2 deletions

diff --git a/src/nvim/tui/tui.c b/src/nvim/tui/tui.c
index 9fea6442a9..4097b770c9 100644
--- a/src/nvim/tui/tui.c
+++ b/src/nvim/tui/tui.c
@@ -145,6 +145,7 @@ struct TUIData {
   } unibi_ext;
   char *space_buf;
   bool stopped;
+  int seen_error_exit;
   int width;
   int height;
   bool rgb;
@@ -162,6 +163,7 @@ void tui_start(TUIData **tui_p, int *width, int *height, char **term)
   tui->is_starting = true;
   tui->screenshot = NULL;
   tui->stopped = false;
+  tui->seen_error_exit = 0;
   tui->loop = &main_loop;
   kv_init(tui->invalid_regions);
   signal_watcher_init(tui->loop, &tui->winch_handle, tui);
@@ -384,8 +386,13 @@ static void terminfo_stop(TUIData *tui)
   unibi_out_ext(tui, tui->unibi_ext.disable_extended_keys);
   // May restore old title before exiting alternate screen.
   tui_set_title(tui, (String)STRING_INIT);
-  // Exit alternate screen.
-  unibi_out(tui, unibi_exit_ca_mode);
+  // if nvim exited with nonzero status, without indicated this was an
+  // intentional exit (like `:1cquit`), it likely was an internal failure.
+  // Don't clobber the stderr error message in this case.
+  if (ui_client_exit_status == tui->seen_error_exit) {
+    // Exit alternate screen.
+    unibi_out(tui, unibi_exit_ca_mode);
+  }
   if (tui->cursor_color_changed) {
     unibi_out_ext(tui, tui->unibi_ext.reset_cursor_color);
   }
@@ -443,6 +450,11 @@ static void tui_terminal_stop(TUIData *tui)
   terminfo_stop(tui);
 }
 
+void tui_error_exit(TUIData *tui, Integer status)
+{
+  tui->seen_error_exit = (int)status;
+}
+
 void tui_stop(TUIData *tui)
 {
   tui_terminal_stop(tui);