Fix inline text span semantics (#34434)

packages/flutter/lib/src/rendering/paragraph.dart

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:math' as math;
 import 'dart:ui' as ui show Gradient, Shader, TextBox, PlaceholderAlignment;
 
 import 'package:flutter/foundation.dart';
@@ -766,12 +767,23 @@ class RenderParagraph extends RenderBox
       final TextDirection initialDirection = currentDirection;
       final TextSelection selection = TextSelection(baseOffset: start, extentOffset: end);
       final List<ui.TextBox> rects = getBoxesForSelection(selection);
-      Rect rect;
-      for (ui.TextBox textBox in rects) {
-        rect ??= textBox.toRect();
+      if (rects.isEmpty) {
+        return null;
+      }
+      Rect rect = rects.first.toRect();
+      currentDirection = rects.first.direction;
+      for (ui.TextBox textBox in rects.skip(1)) {
         rect = rect.expandToInclude(textBox.toRect());
         currentDirection = textBox.direction;
       }
+      // Any of the text boxes may have had infinite dimensions.
+      // We shouldn't pass infinite dimensions up to the bridges.
+      rect = Rect.fromLTWH(
+        math.max(0.0, rect.left),
+        math.max(0.0, rect.top),
+        math.min(rect.width, constraints.maxWidth),
+        math.min(rect.height, constraints.maxHeight),
+      );
       // round the current rectangle to make this API testable and add some
       // padding so that the accessibility rects do not overlap with the text.
       // TODO(jonahwilliams): implement this for all text accessibility rects.
@@ -798,12 +810,18 @@ class RenderParagraph extends RenderBox
       if (current != start) {
         final SemanticsNode node = SemanticsNode();
         final SemanticsConfiguration configuration = buildSemanticsConfig(current, start);
+        if (configuration == null) {
+          continue;
+        }
         node.updateWith(config: configuration);
         node.rect = currentRect;
         newChildren.add(node);
       }
       final dynamic inlineElement = _inlineSemanticsElements[j];
       final SemanticsConfiguration configuration = buildSemanticsConfig(start, end);
+      if (configuration == null) {
+        continue;
+      }
       if (inlineElement != null) {
         // Add semantics for this recognizer.
         final SemanticsNode node = SemanticsNode();
@@ -842,9 +860,11 @@ class RenderParagraph extends RenderBox
     if (current < rawLabel.length) {
       final SemanticsNode node = SemanticsNode();
       final SemanticsConfiguration configuration = buildSemanticsConfig(current, rawLabel.length);
-      node.updateWith(config: configuration);
-      node.rect = currentRect;
-      newChildren.add(node);
+      if (configuration != null) {
+        node.updateWith(config: configuration);
+        node.rect = currentRect;
+        newChildren.add(node);
+      }
     }
     node.updateWith(config: config, childrenInInversePaintOrder: newChildren);
   }

packages/flutter/lib/src/semantics/semantics.dart

@@ -1162,6 +1162,7 @@ class SemanticsNode extends AbstractNode with DiagnosticableTreeMixin {
   Rect _rect = Rect.zero;
   set rect(Rect value) {
     assert(value != null);
+    assert(value.isFinite, '$this (with $owner) tried to set a non-finite rect.');
     if (_rect != value) {
       _rect = value;
       _markDirty();
@@ -2178,6 +2179,7 @@ class _BoxEdge implements Comparable<_BoxEdge> {
     @required this.node,
   }) : assert(isLeadingEdge != null),
        assert(offset != null),
+       assert(offset.isFinite),
        assert(node != null);
 
   /// True if the edge comes before the seconds edge along the traversal
@@ -2384,6 +2386,7 @@ Offset _pointInParentCoordinates(SemanticsNode node, Offset point) {
 List<SemanticsNode> _childrenInDefaultOrder(List<SemanticsNode> children, TextDirection textDirection) {
   final List<_BoxEdge> edges = <_BoxEdge>[];
   for (SemanticsNode child in children) {
+    assert(child.rect.isFinite);
     // Using a small delta to shrink child rects removes overlapping cases.
     final Rect childRect = child.rect.deflate(0.1);
     edges.add(_BoxEdge(

packages/flutter/test/widgets/text_test.dart

@@ -185,6 +185,45 @@ void main() {
     semantics.dispose();
   });
 
+  testWidgets('recognizers split semantic node when TextSpan overflows', (WidgetTester tester) async {
+    final SemanticsTester semantics = SemanticsTester(tester);
+    const TextStyle textStyle = TextStyle(fontFamily: 'Ahem');
+    await tester.pumpWidget(
+      SizedBox(
+        height: 10,
+        child: Text.rich(
+          TextSpan(
+            children: <TextSpan>[
+              const TextSpan(text: '\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n'),
+              TextSpan(text: 'world', recognizer: TapGestureRecognizer()..onTap = () { }),
+            ],
+            style: textStyle,
+          ),
+          textDirection: TextDirection.ltr,
+        ),
+      ),
+    );
+    final TestSemantics expectedSemantics = TestSemantics.root(
+      children: <TestSemantics>[
+        TestSemantics.rootChild(
+          children: <TestSemantics>[
+            TestSemantics(
+              label: '\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n',
+              textDirection: TextDirection.ltr,
+            ),
+            TestSemantics(
+              label: 'world',
+              textDirection: TextDirection.ltr,
+              actions: <SemanticsAction>[SemanticsAction.tap]
+            ),
+          ],
+        ),
+      ],
+    );
+    expect(semantics, hasSemantics(expectedSemantics, ignoreTransform: true, ignoreId: true, ignoreRect: true));
+    semantics.dispose();
+  });
+
   testWidgets('recognizers split semantic nodes with text span labels', (WidgetTester tester) async {
     final SemanticsTester semantics = SemanticsTester(tester);
     const TextStyle textStyle = TextStyle(fontFamily: 'Ahem');