patch 9.0.1213: adding a line below the last one does not expand fold

Problem:    Adding a line below the last one does not expand fold.
Solution:   Do not skip mark_adjust() when adding lines below the last one.
            (Brandon Simmons, closes #11832, closes #10698)

src/change.c

@@ -772,14 +772,7 @@ appended_lines(linenr_T lnum, long count)
     void
 appended_lines_mark(linenr_T lnum, long count)
 {
-    // Skip mark_adjust when adding a line after the last one, there can't
+    mark_adjust(lnum + 1, (linenr_T)MAXLNUM, count, 0L);
-    // be marks there. But it's still needed in diff mode.
-    if (lnum + count < curbuf->b_ml.ml_line_count
-#ifdef FEAT_DIFF
-	    || curwin->w_p_diff
-#endif
-	)
-	mark_adjust(lnum + 1, (linenr_T)MAXLNUM, count, 0L);
     changed_lines(lnum + 1, 0, lnum + 1, count);
 }
 
@@ -2142,14 +2135,7 @@ open_line(
 	    goto theend;
 	// Postpone calling changed_lines(), because it would mess up folding
 	// with markers.
-	// Skip mark_adjust when adding a line after the last one, there can't
+	mark_adjust(curwin->w_cursor.lnum + 1, (linenr_T)MAXLNUM, 1L, 0L);
-	// be marks there. But still needed in diff mode.
-	if (curwin->w_cursor.lnum + 1 < curbuf->b_ml.ml_line_count
-#ifdef FEAT_DIFF
-		|| curwin->w_p_diff
-#endif
-	    )
-	    mark_adjust(curwin->w_cursor.lnum + 1, (linenr_T)MAXLNUM, 1L, 0L);
 	did_append = TRUE;
 #ifdef FEAT_PROP_POPUP
 	if ((State & MODE_INSERT) && (State & VREPLACE_FLAG) == 0)

src/register.c

@@ -2208,15 +2208,7 @@ error:
 		if (dir == FORWARD)
 		    curbuf->b_op_start.lnum++;
 	    }
-	    // Skip mark_adjust when adding lines after the last one, there
+	    mark_adjust(curbuf->b_op_start.lnum + (y_type == MCHAR),
-	    // can't be marks there. But still needed in diff mode.
-	    if (curbuf->b_op_start.lnum + (y_type == MCHAR) - 1 + nr_lines
-						 < curbuf->b_ml.ml_line_count
-#ifdef FEAT_DIFF
-						 || curwin->w_p_diff
-#endif
-						 )
-		mark_adjust(curbuf->b_op_start.lnum + (y_type == MCHAR),
 					     (linenr_T)MAXLNUM, nr_lines, 0L);
 
 	    // note changed text for displaying and folding

src/testdir/test_fold.vim

@@ -1683,4 +1683,17 @@ func Test_indent_with_L_command()
 V{zf8=Lu
   bwipe!
 endfunc
+
+" Make sure that when there is a fold at the bottom of the buffer and a newline
+" character is appended to the line, the fold gets expanded (instead of the new
+" line not being part of the fold).
+func Test_expand_fold_at_bottom_of_buffer()
+  new
+  " create a fold on the only line
+  fold
+  execute "normal A\<CR>"
+  call assert_equal([1, 1], range(1, 2)->map('foldlevel(v:val)'))
+
+  bwipe!
+endfunc
 

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1213,
 /**/
     1212,
 /**/