Merge pull request #2520 from Hixie/TextSpan.toString

Fix crash when dumping the app if it uses RichText

examples/stocks/lib/stock_symbol_viewer.dart

@@ -46,6 +46,19 @@ class StockSymbolView extends StatelessComponent {
           ),
           new Text('Market Cap', style: headings),
           new Text('${stock.marketCap}'),
+          new Container(
+            height: 8.0
+          ),
+          new RichText(
+            text: new TextSpan(
+              style: DefaultTextStyle.of(context).merge(new TextStyle(fontSize: 8.0)),
+              text: 'Prices may be delayed by ',
+              children: <TextSpan>[
+                new TextSpan(text: 'several', style: new TextStyle(fontStyle: FontStyle.italic)),
+                new TextSpan(text: ' years.'),
+              ]
+            )
+          ),
         ],
         justifyContent: FlexJustifyContent.collapse
       )

packages/flutter/lib/services.dart

@@ -12,6 +12,7 @@
 library services;
 
 export 'src/services/activity.dart';
+export 'src/services/assertions.dart';
 export 'src/services/asset_bundle.dart';
 export 'src/services/binding.dart';
 export 'src/services/fetch.dart';

packages/flutter/lib/src/painting/text_painter.dart

@@ -5,6 +5,7 @@
 import 'dart:ui' as ui show Paragraph, ParagraphBuilder, ParagraphStyle, TextBox;
 
 import 'package:flutter/gestures.dart';
+import 'package:flutter/services.dart';
 
 import 'basic_types.dart';
 import 'text_editing.dart';
@@ -51,6 +52,7 @@ class TextSpan {
   final GestureRecognizer recognizer;
 
   void build(ui.ParagraphBuilder builder) {
+    assert(debugAssertValid());
     final bool hasStyle = style != null;
     if (hasStyle)
       builder.pushStyle(style.textStyle);
@@ -81,6 +83,7 @@ class TextSpan {
   }
 
   TextSpan getSpanForPosition(TextPosition position) {
+    assert(debugAssertValid());
     TextAffinity affinity = position.affinity;
     int targetOffset = position.offset;
     int offset = 0;
@@ -101,6 +104,7 @@ class TextSpan {
   }
 
   String toPlainText() {
+    assert(debugAssertValid());
     StringBuffer buffer = new StringBuffer();
     visitTextSpan((TextSpan span) {
       buffer.write(span.text);
@@ -113,15 +117,47 @@ class TextSpan {
     StringBuffer buffer = new StringBuffer();
     buffer.writeln('$prefix$runtimeType:');
     String indent = '$prefix  ';
+    if (style != null)
       buffer.writeln(style.toString(indent));
     if (text != null)
       buffer.writeln('$indent"$text"');
-    if (children != null)
-      for (TextSpan child in children)
-        buffer.writeln(child.toString(indent));
+    if (children != null) {
+      for (TextSpan child in children) {
+        if (child != null) {
+          buffer.write(child.toString(indent));
+        } else {
+          buffer.writeln('$indent<null>');
+        }
+      }
+    }
+    if (style == null && text == null && children == null)
+      buffer.writeln('$indent(empty)');
     return buffer.toString();
   }
 
+  bool debugAssertValid() {
+    assert(() {
+      if (!visitTextSpan((TextSpan span) {
+        if (span.children != null) {
+          for (TextSpan child in span.children) {
+            if (child == null)
+              return false;
+          }
+        }
+        return true;
+      })) {
+        throw new FlutterError(
+          'TextSpan contains a null child.\n'
+          'A TextSpan object with a non-null child list should not have any nulls in its child list.\n'
+          'The full text in question was:\n'
+          '${toString("  ")}'
+        );
+      }
+      return true;
+    });
+    return true;
+  }
+
   bool operator ==(dynamic other) {
     if (identical(this, other))
       return true;
@@ -149,6 +185,7 @@ class TextPainter {
   /// The (potentially styled) text to paint.
   TextSpan get text => _text;
   void set text(TextSpan value) {
+    assert(value == null || value.debugAssertValid());
     if (_text == value)
       return;
     _text = value;

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

@@ -15,6 +15,7 @@ class RenderParagraph extends RenderBox {
     TextSpan text
   ) : _textPainter = new TextPainter(text) {
     assert(text != null);
+    assert(text.debugAssertValid());
   }
 
   final TextPainter _textPainter;
@@ -24,6 +25,7 @@ class RenderParagraph extends RenderBox {
   /// The text to display
   TextSpan get text => _textPainter.text;
   void set text(TextSpan value) {
+    assert(value.debugAssertValid());
     if (_textPainter.text == value)
       return;
     _textPainter.text = value;

packages/flutter/lib/src/services/assertions.dart

@@ -0,0 +1,9 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+class FlutterError extends AssertionError {
+  FlutterError(this.message);
+  final String message;
+  String toString() => message;
+}

packages/flutter/test/painting/text_span_test.dart

@@ -27,4 +27,38 @@ void main() {
     expect(b1 == a2, isFalse);
     expect(c1 == b2, isFalse);
   });
+
+  test("TextSpan ", () {
+    final TextSpan test = new TextSpan(
+      text: 'a',
+      style: new TextStyle(
+        fontSize: 10.0
+      ),
+      children: <TextSpan>[
+        new TextSpan(
+          text: 'b',
+          children: <TextSpan>[
+            new TextSpan()
+          ]
+        ),
+        null,
+        new TextSpan(
+          text: 'c'
+        ),
+      ]
+    );
+    expect(test.toString(), equals(
+      'TextSpan:\n'
+      '  inherit: true\n'
+      '  size: 10.0\n'
+      '  "a"\n'
+      '  TextSpan:\n'
+      '    "b"\n'
+      '    TextSpan:\n'
+      '      (empty)\n'
+      '  <null>\n'
+      '  TextSpan:\n'
+      '    "c"\n'
+    ));
+  });
 }