Fix bug where appending to a nested block list before an outdented sibling failed

pkgs/yaml_edit/CHANGELOG.md

@@ -1,4 +1,5 @@
 ## 2.2.5-wip
+- Fix bug where appending to a nested block list before an outdented sibling threw an exception ([#2481](https://github.com/dart-lang/tools/issues/2481)).
 
 ## 2.2.4
 

pkgs/yaml_edit/lib/src/list_mutations.dart

@@ -121,8 +121,8 @@ SourceEdit _appendToBlockList(
   // Adjusts offset to after the trailing newline of the last entry, if it
   // exists
   if (list.isNotEmpty) {
-    final lastValueSpanEnd = list.nodes.last.span.end.offset;
-    final nextNewLineIndex = yaml.indexOf('\n', lastValueSpanEnd - 1);
+    final lastValueSpanEnd = getContentSensitiveEnd(list.nodes.last);
+    final nextNewLineIndex = yaml.indexOf('\n', lastValueSpanEnd);
     if (nextNewLineIndex == -1) {
       formattedValue = getLineEnding(yaml) + formattedValue;
     } else {

pkgs/yaml_edit/test/append_test.dart

@@ -218,6 +218,35 @@ b:
 '''));
     });
 
+    test('block append nested to list', () {
+      final yamlEditor = YamlEditor('''
+family:
+  - title: Parent
+    children:
+      - title: kid1
+      - title: kid2
+  - title: Uncle
+''');
+
+      expect(
+          () => yamlEditor
+              .appendToList(['family', 0, 'children'], {'title': 'kid3'}),
+          returnsNormally);
+      expectYamlBuilderValue(yamlEditor, {
+        'family': [
+          {
+            'title': 'Parent',
+            'children': [
+              {'title': 'kid1'},
+              {'title': 'kid2'},
+              {'title': 'kid3'},
+            ],
+          },
+          {'title': 'Uncle'},
+        ]
+      });
+    });
+
     test('block append nested and with comments', () {
       final yamlEditor = YamlEditor('''
 a: