vim-patch:9.1.0265: console dialog cannot save unnamed buffers (#28185)

Problem:  console dialog cannot save unnamed buffers
Solution: set bufname before save (glepnir). Define dialog_con_gui
          to test for GUI+Console dialog support, use it to skip
          the test when the GUI feature has been defined.

Note: The dialog_changed() function will also try to call the
browse_save_fname() function, when FEAT_BROWSE is defined (which is only
defined in a GUI build of Vim). This will eventually lead to a call of
do_browse(), which causes an error message if a GUI is not currently
running (see the TODO: in do_browse()) and will then lead to a failure
in Test_goto_buf_with_onfirm().

Therefore, we must disable the Test_goto_buf_with_onfirm(), when the
dialog_con_gui feature is enabled (which basically means dialog feature
for GUI and Console builds, in contrast to the dialog_con and dialog_gui
feature).

(Previously this wasn't a problem, because the test aborted in the YES
case for the :confirm :b XgotoConf case and did therefore not run into
the browse function call)

closes: vim/vim#14398

https://github.com/vim/vim/commit/df46115fc839c8912ed60646e86a412e5180ba1d

Co-authored-by: glepnir <glephunter@gmail.com>

2 files changed, 32 insertions, 9 deletions

diff --git a/src/nvim/ex_cmds2.c b/src/nvim/ex_cmds2.c
index d754150089..898c3fb3f9 100644
--- a/src/nvim/ex_cmds2.c
+++ b/src/nvim/ex_cmds2.c
@@ -203,6 +203,7 @@ void dialog_changed(buf_T *buf, bool checkall)
     .append = false,
     .forceit = false,
   };
+  bool empty_buf = buf->b_fname == NULL;
 
   dialog_msg(buff, _("Save changes to \"%s\"?"), buf->b_fname);
   if (checkall) {
@@ -212,10 +213,23 @@ void dialog_changed(buf_T *buf, bool checkall)
   }
 
   if (ret == VIM_YES) {
-    if (buf->b_fname != NULL
-        && check_overwrite(&ea, buf, buf->b_fname, buf->b_ffname, false) == OK) {
+    if (empty_buf) {
+      buf_set_name(buf->b_fnum, "Untitled");
+    }
+
+    if (check_overwrite(&ea, buf, buf->b_fname, buf->b_ffname, false) == OK) {
       // didn't hit Cancel
-      buf_write_all(buf, false);
+      if (buf_write_all(buf, false) == OK) {
+        return;
+      }
+    }
+
+    // restore to empty when write failed
+    if (empty_buf) {
+      XFREE_CLEAR(buf->b_fname);
+      XFREE_CLEAR(buf->b_ffname);
+      XFREE_CLEAR(buf->b_sfname);
+      unchanged(buf, true, false);
     }
   } else if (ret == VIM_NO) {
     unchanged(buf, true, false);
diff --git a/test/old/testdir/test_buffer.vim b/test/old/testdir/test_buffer.vim
index f2a5a228b8..bc8e5eaf7b 100644
--- a/test/old/testdir/test_buffer.vim
+++ b/test/old/testdir/test_buffer.vim
@@ -252,21 +252,30 @@ func Test_goto_buf_with_confirm()
   CheckUnix
   CheckNotGui
   CheckFeature dialog_con
+  " When dialog_con_gui is defined, Vim is compiled with GUI support
+  " and FEAT_BROWSE will be defined, which causes :confirm :b to
+  " call do_browse(), which will try to use a GUI file browser,
+  " which aborts if a GUI is not available.
+  CheckNotFeature dialog_con_gui
   new XgotoConf
   enew
   call setline(1, 'test')
   call assert_fails('b XgotoConf', 'E37:')
   call feedkeys('c', 'L')
   call assert_fails('confirm b XgotoConf', 'E37:')
-  call assert_equal(1, &modified)
-  call assert_equal('', @%)
+  call assert_true(&modified)
+  call assert_true(empty(bufname('%')))
   call feedkeys('y', 'L')
-  call assert_fails('confirm b XgotoConf', ['', 'E37:'])
-  call assert_equal(1, &modified)
-  call assert_equal('', @%)
+  confirm b XgotoConf
+  call assert_equal('XgotoConf', bufname('%'))
+  call assert_equal(['test'], readfile('Untitled'))
+  e Untitled
+  call setline(2, 'test2')
   call feedkeys('n', 'L')
   confirm b XgotoConf
-  call assert_equal('XgotoConf', @%)
+  call assert_equal('XgotoConf', bufname('%'))
+  call assert_equal(['test'], readfile('Untitled'))
+  call delete('Untitled')
   close!
 endfunc