TextSpan has no linkUrl, so a tappable span becomes a link with no href that cannot be focused #194551

Reproduced on Flutter 3.47.4 stable (9584c67), Chrome on macOS. The code involved is unchanged on master 697012a (links below).

Use case

A TextSpan with a TapGestureRecognizer becomes a semantics node with isLink = true, but there is no way to say where the link goes. On web, the engine renders it as an <a> with no href. Such an element is not in the Tab order, a screen reader cannot treat it as a visitable link, and the browser's context menu does not offer to open it in a new tab. In a real app, inline links inside running text (for example "Read the guide today.") are the common case, and they cannot get a real href today.

This is closer to a proposal than a bug: TextSpan has no way to carry a URL.

Code sample:

import 'package:flutter/gestures.dart';
import 'package:flutter/material.dart';

void main() => runApp(
  MaterialApp(
    home: Scaffold(
      body: Text.rich(
        TextSpan(
          children: [
            const TextSpan(text: 'Read '),
            TextSpan(text: 'the guide', recognizer: TapGestureRecognizer()..onTap = () {}),
            const TextSpan(text: ' today.'),
          ],
        ),
      ),
    ),
  ),
);

Steps:

1. Build the sample for web, serve it, and enable semantics (activate the placeholder with document.querySelector('flt-semantics-placeholder').click(), or use a screen reader).
2. Inspect the link's element and the accessibility tree.

Observed DOM and Chrome accessibility tree:

DOM <a id="flt-semantic-node-6" flt-tappable="" style="display: block; …">the guide</a>
AX  link "the guide"            (no url property)

On the framework side, the widget test below prints:

link node: isLink=true linkUrl=null isFocused=Tristate.none actions=1

actions=1 is SemanticsAction.tap alone. The node has no linkUrl, and isFocused is Tristate.none, so it is not focusable.

import 'package:flutter/material.dart';
import 'package:flutter/semantics.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:repro/span_link.dart' as link;

void main() {
  testWidgets('span link', (tester) async {
    final h = tester.ensureSemantics();
    link.main();
    await tester.pump();
    final linkNode = find.semantics.byLabel('the guide').evaluate().single.getSemanticsData();
    debugPrint('link node: isLink=${linkNode.flagsCollection.isLink} linkUrl=${linkNode.linkUrl} isFocused=${linkNode.flagsCollection.isFocused} actions=${linkNode.actions}');
    h.dispose();
  });
}

Playwright's getByRole('link') does not match the element, because an <a> without href has no implicit link role in its ARIA computation. Chrome's accessibility tree still reports link.

Where it comes from (unchanged on master):

• painting/inline_span.dart L58-L103: InlineSpanSemanticsInformation carries text, label, identifier, string attributes and a recognizer, but no URL. painting/text_span.dart has no linkUrl either.
• rendering/paragraph.dart L1419-L1425 (3.47.4), L1435-L1441 on master: a span with a TapGestureRecognizer or DoubleTapGestureRecognizer gets onTap and isLink = true. Nothing can set linkUrl, and the node is not marked focusable.
• On the engine side, semantics/link.dart L30-L36: SemanticLink sets href only when hasLinkUrl.

Today the only way to get a real href is a WidgetSpan whose child is MergeSemantics(Semantics(link: true, linkUrl: …, child: …)). This is the shape url_launcher_web's Link uses (url_launcher_web/lib/src/link.dart L119-L123). It costs line wrapping inside the label, and the paragraph must be assembled per span to keep the reading order: when we tried it, that needed a semanticsIdentifier on a plain sibling span.

Proposal

Add Uri? linkUrl to TextSpan (and to InlineSpanSemanticsInformation), and in RenderParagraph's per-span semantics assembly set configuration.linkUrl, plus isFocusable when there is a tap handler. On web, SemanticLink would then write the href, and the link would be focusable, reachable with Tab, and announced as a visitable link.

Related issues

• [Google3 Bug]: [a11y] [Android] Talkback can't focus text sections with inline links on Android mobile web #174712 (open): TalkBack cannot focus text sections that have inline links, on mobile web.
• SemanticLink causes full page navigation for same-origin URLs on Flutter Web #183620 (closed): SemanticLink causes a full page navigation for same-origin URLs.