[flutter_markdown] Ensure customize nested bullet list style. (#6384)

See flutter/flutter#145670 .

packages/flutter_markdown/CHANGELOG.md

@@ -1,3 +1,9 @@
+## 0.7.0
+
+* **BREAKING CHANGES**:
+  * Replaces parameters at `bulletBuilder` with `MarkdownBulletParameters`.
+  * Introduces a new parameter `nestLevel` that exposes the bullet item's nesting level.
+
 ## 0.6.23
 
 * Gracefully handle image dimension parsing failures.

packages/flutter_markdown/example/lib/demos/custom_bullet_list_demo.dart

@@ -0,0 +1,84 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// TODO(goderbauer): Restructure the examples to avoid this ignore, https://github.com/flutter/flutter/issues/110208.
+// ignore_for_file: avoid_implementing_value_types
+
+import 'package:flutter/material.dart';
+import 'package:flutter_markdown/flutter_markdown.dart';
+import '../shared/markdown_demo_widget.dart';
+
+// ignore_for_file: public_member_api_docs
+
+const String _markdownData = '''
+# Custom Ordered List Demo
+
+## Unordered List
+
+- first
+- second
+   - first
+      - first
+      - second
+   - first
+      - second
+
+## Ordered List
+
+1. first
+2. second
+   1. first
+      1. first
+      2. second
+   1. first
+      1. second
+''';
+
+const String _notes = '''
+# Custom Bullet List Demo
+---
+
+## Overview
+
+This is the custom bullet list demo. This demo shows how to customize the bullet list style.
+This demo example is being preserved for reference purposes.
+''';
+
+class CustomBulletListDemo extends StatelessWidget
+    implements MarkdownDemoWidget {
+  const CustomBulletListDemo({super.key});
+
+  static const String _title = 'Custom Bullet List Demo';
+
+  @override
+  String get title => CustomBulletListDemo._title;
+
+  @override
+  String get description => 'Shows how to customize the bullet list style.';
+
+  @override
+  Future<String> get data => Future<String>.value(_markdownData);
+
+  @override
+  Future<String> get notes => Future<String>.value(_notes);
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      body: SafeArea(
+        child: Markdown(
+          data: _markdownData,
+          bulletBuilder: (MarkdownBulletParameters parameters) => FittedBox(
+            fit: BoxFit.scaleDown,
+            child: switch (parameters.style) {
+              BulletStyle.unorderedList => const Text('・'),
+              BulletStyle.orderedList =>
+                Text('${parameters.nestLevel}-${parameters.index + 1}.'),
+            },
+          ),
+        ),
+      ),
+    );
+  }
+}

packages/flutter_markdown/example/lib/screens/home_screen.dart

@@ -5,6 +5,7 @@
 import 'package:flutter/material.dart';
 import '../demos/basic_markdown_demo.dart';
 import '../demos/centered_header_demo.dart';
+import '../demos/custom_bullet_list_demo.dart';
 import '../demos/extended_emoji_demo.dart';
 import '../demos/markdown_body_shrink_wrap_demo.dart';
 import '../demos/minimal_markdown_demo.dart';
@@ -30,6 +31,7 @@ class HomeScreen extends StatelessWidget {
     OriginalMarkdownDemo(),
     const CenteredHeaderDemo(),
     const MarkdownBodyShrinkWrapDemo(),
+    const CustomBulletListDemo(),
   ];
 
   @override

packages/flutter_markdown/lib/src/builder.dart

@@ -611,8 +611,15 @@ class MarkdownBuilder implements md.NodeVisitor {
     if (bulletBuilder != null) {
       return Padding(
         padding: styleSheet.listBulletPadding!,
-        child: bulletBuilder!(index,
-            isUnordered ? BulletStyle.unorderedList : BulletStyle.orderedList),
+        child: bulletBuilder!(
+          MarkdownBulletParameters(
+            index: index,
+            style: isUnordered
+                ? BulletStyle.unorderedList
+                : BulletStyle.orderedList,
+            nestLevel: _listIndents.length - 1,
+          ),
+        ),
       );
     }
 

packages/flutter_markdown/lib/src/widget.dart

@@ -46,7 +46,30 @@ typedef MarkdownCheckboxBuilder = Widget Function(bool value);
 /// Signature for custom bullet widget.
 ///
 /// Used by [MarkdownWidget.bulletBuilder]
-typedef MarkdownBulletBuilder = Widget Function(int index, BulletStyle style);
+typedef MarkdownBulletBuilder = Widget Function(
+  MarkdownBulletParameters parameters,
+);
+
+/// An parameters of [MarkdownBulletBuilder].
+///
+/// Used by [MarkdownWidget.bulletBuilder]
+class MarkdownBulletParameters {
+  /// Creates a new instance of [MarkdownBulletParameters].
+  const MarkdownBulletParameters({
+    required this.index,
+    required this.style,
+    required this.nestLevel,
+  });
+
+  /// The index of the bullet on that nesting level.
+  final int index;
+
+  /// The style of the bullet.
+  final BulletStyle style;
+
+  /// The nest level of the bullet.
+  final int nestLevel;
+}
 
 /// Enumeration sent to the user when calling [MarkdownBulletBuilder]
 ///

packages/flutter_markdown/pubspec.yaml

@@ -4,7 +4,7 @@ description: A Markdown renderer for Flutter. Create rich text output,
   formatted with simple Markdown tags.
 repository: https://github.com/flutter/packages/tree/main/packages/flutter_markdown
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+flutter_markdown%22
-version: 0.6.23
+version: 0.7.0
 
 environment:
   sdk: ^3.3.0

packages/flutter_markdown/test/list_test.dart

@@ -94,6 +94,35 @@ void defineTests() {
         ]);
       },
     );
+
+    testWidgets('custom bullet builder', (WidgetTester tester) async {
+      const String data =
+          '* Item 1\n   * Item 2\n      * Item 3\n   * Item 4\n* Item 5';
+      Widget builder(MarkdownBulletParameters parameters) => Text(
+            '${parameters.index} ${parameters.style == BulletStyle.orderedList ? 'ordered' : 'unordered'} ${parameters.nestLevel}',
+          );
+
+      await tester.pumpWidget(
+        boilerplate(
+          Markdown(data: data, bulletBuilder: builder),
+        ),
+      );
+
+      final Iterable<Widget> widgets = tester.allWidgets;
+
+      expectTextStrings(widgets, <String>[
+        '0 unordered 0',
+        'Item 1',
+        '0 unordered 1',
+        'Item 2',
+        '0 unordered 2',
+        'Item 3',
+        '1 unordered 1',
+        'Item 4',
+        '1 unordered 0',
+        'Item 5',
+      ]);
+    });
   });
 
   group('Ordered List', () {
@@ -135,6 +164,35 @@ void defineTests() {
       final Iterable<Widget> widgets = tester.allWidgets;
       expectTextStrings(widgets, <String>['1.', 'one', 'two']);
     });
+
+    testWidgets('custom bullet builder', (WidgetTester tester) async {
+      const String data =
+          '1. Item 1\n   1. Item 2\n      1. Item 3\n   1. Item 4\n1. Item 5';
+      Widget builder(MarkdownBulletParameters parameters) => Text(
+            '${parameters.index} ${parameters.style == BulletStyle.orderedList ? 'ordered' : 'unordered'} ${parameters.nestLevel}',
+          );
+
+      await tester.pumpWidget(
+        boilerplate(
+          Markdown(data: data, bulletBuilder: builder),
+        ),
+      );
+
+      final Iterable<Widget> widgets = tester.allWidgets;
+
+      expectTextStrings(widgets, <String>[
+        '0 ordered 0',
+        'Item 1',
+        '0 ordered 1',
+        'Item 2',
+        '0 ordered 2',
+        'Item 3',
+        '1 ordered 1',
+        'Item 4',
+        '1 ordered 0',
+        'Item 5',
+      ]);
+    });
   });
 
   group('Task List', () {
@@ -161,8 +219,8 @@ void defineTests() {
 
     testWidgets('custom bullet builder', (WidgetTester tester) async {
       const String data = '* Item 1\n* Item 2\n1) Item 3\n2) Item 4';
-      Widget builder(int index, BulletStyle style) => Text(
-          '$index ${style == BulletStyle.orderedList ? 'ordered' : 'unordered'}');
+      Widget builder(MarkdownBulletParameters parameters) => Text(
+          '${parameters.index} ${parameters.style == BulletStyle.orderedList ? 'ordered' : 'unordered'}');
 
       await tester.pumpWidget(
         boilerplate(