vim-patch:8.2.2489: current buffer is wrong after deletebufline() fails

Problem:    current buffer is wrong after deletebufline() fails to delete a
            line in another buffer.
Solution:   Restore the current buffer.
https://github.com/vim/vim/commit/963ffa0a5a6091655ed72b4590ec5d5a1653bce8

2 files changed, 27 insertions, 17 deletions

diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index fae5711b9c..3cc71a39f6 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -1629,27 +1629,26 @@ static void f_deletebufline(typval_T *argvars, typval_T *rettv, FunPtr fptr)
 
   if (u_save(first - 1, last + 1) == FAIL) {
     rettv->vval.v_number = 1;  // FAIL
-    return;
-  }
-
-  for (linenr_T lnum = first; lnum <= last; lnum++) {
-    ml_delete(first, true);
-  }
+  } else {
+    for (linenr_T lnum = first; lnum <= last; lnum++) {
+      ml_delete(first, true);
+    }
 
-  FOR_ALL_TAB_WINDOWS(tp, wp) {
-    if (wp->w_buffer == buf) {
-      if (wp->w_cursor.lnum > last) {
-        wp->w_cursor.lnum -= count;
-      } else if (wp->w_cursor.lnum> first) {
-        wp->w_cursor.lnum = first;
-      }
-      if (wp->w_cursor.lnum > wp->w_buffer->b_ml.ml_line_count) {
-        wp->w_cursor.lnum = wp->w_buffer->b_ml.ml_line_count;
+    FOR_ALL_TAB_WINDOWS(tp, wp) {
+      if (wp->w_buffer == buf) {
+        if (wp->w_cursor.lnum > last) {
+          wp->w_cursor.lnum -= count;
+        } else if (wp->w_cursor.lnum> first) {
+          wp->w_cursor.lnum = first;
+        }
+        if (wp->w_cursor.lnum > wp->w_buffer->b_ml.ml_line_count) {
+          wp->w_cursor.lnum = wp->w_buffer->b_ml.ml_line_count;
+        }
       }
     }
+    check_cursor_col();
+    deleted_lines_mark(first, count);
   }
-  check_cursor_col();
-  deleted_lines_mark(first, count);
 
   if (!is_curbuf) {
     curbuf = curbuf_save;
diff --git a/src/nvim/testdir/test_bufline.vim b/src/nvim/testdir/test_bufline.vim
index 076f03fdd8..e038bce08e 100644
--- a/src/nvim/testdir/test_bufline.vim
+++ b/src/nvim/testdir/test_bufline.vim
@@ -112,6 +112,17 @@ func Test_deletebufline()
   call assert_equal(0, deletebufline(b, 1))
   call assert_equal(['b', 'c'], getbufline(b, 1, 2))
   exe "bwipe! " . b
+
+  edit XbufOne
+  let one = bufnr()
+  call setline(1, ['a', 'b', 'c'])
+  setlocal nomodifiable
+  split XbufTwo
+  let two = bufnr()
+  call assert_fails('call deletebufline(one, 1)', 'E21:')
+  call assert_equal(two, bufnr())
+  bwipe! XbufTwo
+  bwipe! XbufOne
 endfunc
 
 func Test_appendbufline_redraw()