Exception thrown "Failed to produce valid YAML after modification." on adding to list

[slashblog]

I have the following YAML:

family:
  - title: Parent
    children:
      - title: kid1
      - title: kid2
  - title: Uncle

on adding another kid like so:

editor.appendToList(['family', 0, 'children'], {'title': 'kid3'});

the following exception is thrown:

Assertion failed: (package:yaml_edit) Failed to produce valid YAML after modification.

The full code to reproduce the issue is as follows:

import 'package:yaml_edit/yaml_edit.dart';

void main() {
  final yaml = '''
family:
  - title: Parent
    children:
      - title: kid1
      - title: kid2
  - title: Uncle
''';

  print('--- BEFORE ---');
  print(yaml);

  final editor = YamlEditor(yaml);

  editor.appendToList(['family', 0, 'children'], {'title': 'kid3'});

  print('--- AFTER (buggy yaml_edit) ---');
  print(editor.toString());

  print('--- EXPECTED ---');
  print('''
family:
  - title: Parent
    children:
      - title: kid1
      - title: kid2
      - title: kid3
  - title: Uncle
''');
}

The issue is coming because:

list.nodes.last.span.end.offset gives offset for character just before "- title: Uncle".

The fix is following:

#2482

[sigurdm]

LGTM with a few minor cleanups:

1. CHANGELOG phrasing:
   Please update CHANGELOG.md to use -wip and phrase the bullet as a fix rather than quoting the issue title:

   ## 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)).

[slashblog]

LGTM with a few minor cleanups:

1. **CHANGELOG phrasing**:
   Please update `CHANGELOG.md` to use `-wip` and phrase the bullet as a fix rather than quoting the issue title:
   ## 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)).

Made changes as per your suggestions.