[flutter_markdown] Fix WidgetSpan Support in MarkdownElementBuilder

packages/flutter_markdown/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.6.21
+
+* Fixes support for `WidgetSpan` in `Text.rich` elements inside `MarkdownElementBuilder`.
+
 ## 0.6.20+1
 
 * Updates minimum supported SDK version to Flutter 3.19.

packages/flutter_markdown/lib/src/builder.dart

@@ -707,52 +707,119 @@ class MarkdownBuilder implements md.NodeVisitor {
     }
   }
 
+  /// Extracts all spans from an inline element and merges them into a single list
+  Iterable<InlineSpan> _getInlineSpans(InlineSpan span) {
+    // If the span is not a TextSpan or it has no children, return the span
+    if (span is! TextSpan || span.children == null) {
+      return <InlineSpan>[span];
+    }
+
+    // Merge the style of the parent with the style of the children
+    final Iterable<InlineSpan> spans =
+        span.children!.map((InlineSpan childSpan) {
+      if (childSpan is TextSpan) {
+        return TextSpan(
+          text: childSpan.text,
+          recognizer: childSpan.recognizer,
+          semanticsLabel: childSpan.semanticsLabel,
+          style: childSpan.style?.merge(span.style),
+        );
+      } else {
+        return childSpan;
+      }
+    });
+
+    return spans;
+  }
+
   /// Merges adjacent [TextSpan] children
   List<Widget> _mergeInlineChildren(
     List<Widget> children,
     TextAlign? textAlign,
   ) {
+    // List of merged text spans and widgets
     final List<Widget> mergedTexts = <Widget>[];
+
     for (final Widget child in children) {
-      if (mergedTexts.isNotEmpty && mergedTexts.last is Text && child is Text) {
-        final Text previous = mergedTexts.removeLast() as Text;
-        final TextSpan previousTextSpan = previous.textSpan! as TextSpan;
-        final List<TextSpan> children = previousTextSpan.children != null
-            ? previousTextSpan.children!
-                .map((InlineSpan span) => span is! TextSpan
-                    ? TextSpan(children: <InlineSpan>[span])
-                    : span)
-                .toList()
-            : <TextSpan>[previousTextSpan];
-        children.add(child.textSpan! as TextSpan);
-        final TextSpan? mergedSpan = _mergeSimilarTextSpans(children);
-        mergedTexts.add(_buildRichText(
-          mergedSpan,
-          textAlign: textAlign,
-        ));
-      } else if (mergedTexts.isNotEmpty &&
-          mergedTexts.last is SelectableText &&
-          child is SelectableText) {
-        final SelectableText previous =
-            mergedTexts.removeLast() as SelectableText;
-        final TextSpan previousTextSpan = previous.textSpan!;
-        final List<TextSpan> children = previousTextSpan.children != null
-            ? List<TextSpan>.from(previousTextSpan.children!)
-            : <TextSpan>[previousTextSpan];
-        if (child.textSpan != null) {
-          children.add(child.textSpan!);
+      // If the list is empty, add the current widget to the list
+      if (mergedTexts.isEmpty) {
+        mergedTexts.add(child);
+        continue;
+      }
+
+      // Remove last widget from the list to merge it with the current widget
+      final Widget last = mergedTexts.removeLast();
+
+      // Extracted spans from the last and the current widget
+      List<InlineSpan> spans = <InlineSpan>[];
+
+      // Extract the text spans from the last widget
+      if (last is SelectableText) {
+        final TextSpan span = last.textSpan!;
+        spans.addAll(_getInlineSpans(span));
+      } else if (last is Text) {
+        final InlineSpan span = last.textSpan!;
+        spans.addAll(_getInlineSpans(span));
+      } else if (last is RichText) {
+        final InlineSpan span = last.text;
+        spans.addAll(_getInlineSpans(span));
+      } else {
+        // If the last widget is not a text widget,
+        // add both the last and the current widget to the list
+        mergedTexts.addAll(<Widget>[last, child]);
+        continue;
+      }
+
+      // Extract the text spans from the current widget
+      if (child is Text) {
+        final InlineSpan span = child.textSpan!;
+        spans.addAll(_getInlineSpans(span));
+      } else if (child is SelectableText) {
+        final TextSpan span = child.textSpan!;
+        spans.addAll(_getInlineSpans(span));
+      } else if (child is RichText) {
+        final InlineSpan span = child.text;
+        spans.addAll(_getInlineSpans(span));
+      } else {
+        // If the current widget is not a text widget,
+        // add both the last and the current widget to the list
+        mergedTexts.addAll(<Widget>[last, child]);
+        continue;
+      }
+
+      if (spans.isNotEmpty) {
+        // Merge similar text spans
+        spans = _mergeSimilarTextSpans(spans);
+
+        // Create a new text widget with the merged text spans
+        InlineSpan child;
+        if (spans.length == 1) {
+          child = spans.first;
+        } else {
+          child = TextSpan(children: spans);
+        }
+
+        // Add the new text widget to the list
+        if (selectable) {
+          mergedTexts.add(SelectableText.rich(
+            TextSpan(children: spans),
+            textScaler: styleSheet.textScaler,
+            textAlign: textAlign ?? TextAlign.start,
+            onTap: onTapText,
+          ));
+        } else {
+          mergedTexts.add(Text.rich(
+            child,
+            textScaler: styleSheet.textScaler,
+            textAlign: textAlign ?? TextAlign.start,
+          ));
         }
-        final TextSpan? mergedSpan = _mergeSimilarTextSpans(children);
-        mergedTexts.add(
-          _buildRichText(
-            mergedSpan,
-            textAlign: textAlign,
-          ),
-        );
       } else {
+        // If no text spans were found, add the current widget to the list
         mergedTexts.add(child);
       }
     }
+
     return mergedTexts;
   }
 
@@ -827,35 +894,44 @@ class MarkdownBuilder implements md.NodeVisitor {
   }
 
   /// Combine text spans with equivalent properties into a single span.
-  TextSpan? _mergeSimilarTextSpans(List<TextSpan>? textSpans) {
-    if (textSpans == null || textSpans.length < 2) {
-      return TextSpan(children: textSpans);
+  List<InlineSpan> _mergeSimilarTextSpans(List<InlineSpan> textSpans) {
+    if (textSpans.length < 2) {
+      return textSpans;
     }
 
-    final List<TextSpan> mergedSpans = <TextSpan>[textSpans.first];
+    final List<InlineSpan> mergedSpans = <InlineSpan>[];
 
     for (int index = 1; index < textSpans.length; index++) {
-      final TextSpan nextChild = textSpans[index];
-      if (nextChild.recognizer == mergedSpans.last.recognizer &&
-          nextChild.semanticsLabel == mergedSpans.last.semanticsLabel &&
-          nextChild.style == mergedSpans.last.style) {
-        final TextSpan previous = mergedSpans.removeLast();
+      final InlineSpan previous =
+          mergedSpans.isEmpty ? textSpans.first : mergedSpans.removeLast();
+      final InlineSpan nextChild = textSpans[index];
+
+      final bool previousIsTextSpan = previous is TextSpan;
+      final bool nextIsTextSpan = nextChild is TextSpan;
+      if (!previousIsTextSpan || !nextIsTextSpan) {
+        mergedSpans.addAll(<InlineSpan>[previous, nextChild]);
+        continue;
+      }
+
+      final bool matchStyle = nextChild.recognizer == previous.recognizer &&
+          nextChild.semanticsLabel == previous.semanticsLabel &&
+          nextChild.style == previous.style;
+
+      if (matchStyle) {
         mergedSpans.add(TextSpan(
           text: previous.toPlainText() + nextChild.toPlainText(),
           recognizer: previous.recognizer,
           semanticsLabel: previous.semanticsLabel,
           style: previous.style,
         ));
       } else {
-        mergedSpans.add(nextChild);
+        mergedSpans.addAll(<InlineSpan>[previous, nextChild]);
       }
     }
 
     // When the mergered spans compress into a single TextSpan return just that
     // TextSpan, otherwise bundle the set of TextSpans under a single parent.
-    return mergedSpans.length == 1
-        ? mergedSpans.first
-        : TextSpan(children: mergedSpans);
+    return mergedSpans;
   }
 
   Widget _buildRichText(TextSpan? text, {TextAlign? textAlign, String? key}) {

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: 0.6.20+1
+version: 0.6.21
 
 environment:
   sdk: ^3.3.0

packages/flutter_markdown/test/custom_syntax_test.dart

@@ -77,9 +77,8 @@ void defineTests() {
         );
 
         final Text textWidget = tester.widget(find.byType(Text));
-        final TextSpan span =
-            (textWidget.textSpan! as TextSpan).children![0] as TextSpan;
-        final WidgetSpan widgetSpan = span.children![0] as WidgetSpan;
+        final TextSpan textSpan = textWidget.textSpan! as TextSpan;
+        final WidgetSpan widgetSpan = textSpan.children![0] as WidgetSpan;
         expect(widgetSpan.child, isInstanceOf<Container>());
       },
     );
@@ -133,10 +132,9 @@ void defineTests() {
       final TextSpan textSpan = textWidget.textSpan! as TextSpan;
       final TextSpan start = textSpan.children![0] as TextSpan;
       expect(start.text, 'this test replaces a string with a ');
-      final TextSpan end = textSpan.children![1] as TextSpan;
-      final TextSpan foo = end.children![0] as TextSpan;
+      final TextSpan foo = textSpan.children![1] as TextSpan;
       expect(foo.text, 'foo');
-      final WidgetSpan widgetSpan = end.children![1] as WidgetSpan;
+      final WidgetSpan widgetSpan = textSpan.children![2] as WidgetSpan;
       expect(widgetSpan.child, isInstanceOf<Container>());
     },
   );

packages/flutter_markdown/test/inline_widget_test.dart

@@ -0,0 +1,78 @@
+// 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.
+
+import 'package:flutter/cupertino.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_markdown/flutter_markdown.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:markdown/markdown.dart' as md;
+
+import 'utils.dart';
+
+void main() => defineTests();
+
+void defineTests() {
+  group('InlineWidget', () {
+    testWidgets(
+      'Test inline widget',
+      (WidgetTester tester) async {
+        await tester.pumpWidget(
+          boilerplate(
+            MarkdownBody(
+              data: 'Hello, foo bar',
+              builders: <String, MarkdownElementBuilder>{
+                'sub': SubscriptBuilder(),
+              },
+              extensionSet: md.ExtensionSet(
+                <md.BlockSyntax>[],
+                <md.InlineSyntax>[SubscriptSyntax()],
+              ),
+            ),
+          ),
+        );
+
+        final Text textWidget = tester.firstWidget(find.byType(Text));
+        final TextSpan span = textWidget.textSpan! as TextSpan;
+
+        final TextSpan part1 = span.children![0] as TextSpan;
+        expect(part1.toPlainText(), 'Hello, ');
+
+        final WidgetSpan part2 = span.children![1] as WidgetSpan;
+        expect(part2.alignment, PlaceholderAlignment.middle);
+        expect(part2.child, isA<Text>());
+        expect((part2.child as Text).data, 'foo');
+
+        final TextSpan part3 = span.children![2] as TextSpan;
+        expect(part3.toPlainText(), ' bar');
+      },
+    );
+  });
+}
+
+class SubscriptBuilder extends MarkdownElementBuilder {
+  @override
+  Widget visitElementAfterWithContext(
+    BuildContext context,
+    md.Element element,
+    TextStyle? preferredStyle,
+    TextStyle? parentStyle,
+  ) {
+    return Text.rich(WidgetSpan(
+      alignment: PlaceholderAlignment.middle,
+      child: Text(element.textContent),
+    ));
+  }
+}
+
+class SubscriptSyntax extends md.InlineSyntax {
+  SubscriptSyntax() : super(_pattern);
+
+  static const String _pattern = r'(foo)';
+
+  @override
+  bool onMatch(md.InlineParser parser, Match match) {
+    parser.addNode(md.Element.text('sub', match[1]!));
+    return true;
+  }
+}