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Try a mildly prettier FlutterError and make it less drastic in release mode. (#44967)

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Ian Hickson 2019-11-19 17:35:47 -08:00 committed by GitHub
parent 664350d2a8
commit b75abd9f7e
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5 changed files with 213 additions and 35 deletions
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5
packages/flutter/lib/src/foundation/assertions.dart
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@ -479,6 +479,11 @@ class FlutterErrorDetails extends Diagnosticable {
/// Error class used to report Flutter-specific assertion failures and
/// contract violations.
///
/// See also:
///
/// * <https://flutter.dev/docs/testing/errors>, more information about error
/// handling in Flutter.
class FlutterError extends Error with DiagnosticableTreeMixin implements AssertionError {
/// Create an error message from a string.
///

99
packages/flutter/lib/src/rendering/error.dart
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@ -10,9 +10,6 @@ import 'object.dart';
const double _kMaxWidth = 100000.0;
const double _kMaxHeight = 100000.0;
// Line length to fit small phones without dynamically checking size.
const String _kLine = '\n\n────────────────────\n\n';
/// A render object used as a placeholder when an error occurs.
///
/// The box will be painted in the color given by the
@ -25,8 +22,9 @@ const String _kLine = '\n\n─────────────────
/// [RenderErrorBox.textStyle] and [RenderErrorBox.paragraphStyle] static
/// properties.
///
/// Again to help simplify the class, this box tries to be 100000.0 pixels wide
/// and high, to approximate being infinitely high but without using infinities.
/// Again to help simplify the class, if the parent has left the constraints
/// unbounded, this box tries to be 100000.0 pixels wide and high, to
/// approximate being infinitely high but without using infinities.
class RenderErrorBox extends RenderBox {
/// Creates a RenderErrorBox render object.
///
@ -45,13 +43,10 @@ class RenderErrorBox extends RenderBox {
// see the paragraph.dart file and the RenderParagraph class.
final ui.ParagraphBuilder builder = ui.ParagraphBuilder(paragraphStyle);
builder.pushStyle(textStyle);
builder.addText(
'$message$_kLine$message$_kLine$message$_kLine$message$_kLine$message$_kLine$message$_kLine'
'$message$_kLine$message$_kLine$message$_kLine$message$_kLine$message$_kLine$message'
);
builder.addText(message);
_paragraph = builder.build();
}
} catch (e) {
} catch (error) {
// Intentionally left empty.
}
}
@ -82,39 +77,87 @@ class RenderErrorBox extends RenderBox {
size = constraints.constrain(const Size(_kMaxWidth, _kMaxHeight));
}
/// The distance to place around the text.
///
/// This is intended to ensure that if the [RenderErrorBox] is placed at the top left
/// of the screen, under the system's status bar, the error text is still visible in
/// the area below the status bar.
///
/// The padding is ignored if the error box is smaller than the padding.
///
/// See also:
///
/// * [minimumWidth], which controls how wide the box must be before the
// horizontal padding is applied.
static EdgeInsets padding = const EdgeInsets.fromLTRB(64.0, 96.0, 64.0, 12.0);
/// The width below which the horizontal padding is not applied.
///
/// If the left and right padding would reduce the available width to less than
/// this value, then the text is rendered flush with the left edge.
static double minimumWidth = 200.0;
/// The color to use when painting the background of [RenderErrorBox] objects.
static Color backgroundColor = const Color(0xF0900000);
///
/// Defaults to red in debug mode, a light gray otherwise.
static Color backgroundColor = _initBackgroundColor();
static Color _initBackgroundColor() {
Color result = const Color(0xF0C0C0C0);
assert(() {
result = const Color(0xF0900000);
return true;
}());
return result;
}
/// The text style to use when painting [RenderErrorBox] objects.
static ui.TextStyle textStyle = ui.TextStyle(
color: const Color(0xFFFFFF66),
fontFamily: 'monospace',
fontSize: 14.0,
fontWeight: FontWeight.bold,
);
///
/// Defaults to a yellow monospace font in debug mode, and a dark gray
/// sans-serif font otherwise.
static ui.TextStyle textStyle = _initTextStyle();
static ui.TextStyle _initTextStyle() {
ui.TextStyle result = ui.TextStyle(
color: const Color(0xFF303030),
fontFamily: 'sans-serif',
fontSize: 18.0,
);
assert(() {
result = ui.TextStyle(
color: const Color(0xFFFFFF66),
fontFamily: 'monospace',
fontSize: 14.0,
fontWeight: FontWeight.bold,
);
return true;
}());
return result;
}
/// The paragraph style to use when painting [RenderErrorBox] objects.
static ui.ParagraphStyle paragraphStyle = ui.ParagraphStyle(
height: 1.0,
textDirection: TextDirection.ltr,
textAlign: TextAlign.left,
);
@override
void paint(PaintingContext context, Offset offset) {
try {
context.canvas.drawRect(offset & size, Paint() .. color = backgroundColor);
double width;
if (_paragraph != null) {
// See the comment in the RenderErrorBox constructor. This is not the
// code you want to be copying and pasting. :-)
if (parent is RenderBox) {
final RenderBox parentBox = parent;
width = parentBox.size.width;
} else {
width = size.width;
double width = size.width;
double left = 0.0;
double top = 0.0;
if (width > padding.left + minimumWidth + padding.right) {
width -= padding.left + padding.right;
left += padding.left;
}
_paragraph.layout(ui.ParagraphConstraints(width: width));
context.canvas.drawParagraph(_paragraph, offset);
if (size.height > padding.top + _paragraph.height + padding.bottom) {
top += padding.top;
}
context.canvas.drawParagraph(_paragraph, offset + Offset(left, top));
}
} catch (e) {
// Intentionally left empty.

83
packages/flutter/lib/src/widgets/framework.dart
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@ -3810,13 +3810,71 @@ typedef ErrorWidgetBuilder = Widget Function(FlutterErrorDetails details);
/// where the problem lies. Exceptions are also logged to the console, which you
/// can read using `flutter logs`. The console will also include additional
/// information such as the stack trace for the exception.
///
/// It is possible to override this widget.
///
/// {@tool snippet --template=freeform}
/// ```dart
/// import 'package:flutter/material.dart';
///
/// void main() {
/// ErrorWidget.builder = (FlutterErrorDetails details) {
/// bool inDebug = false;
/// assert(() { inDebug = true; return true; }());
/// // In debug mode, use the normal error widget which shows
/// // the error message:
/// if (inDebug)
/// return ErrorWidget(details.exception);
/// // In release builds, show a yellow-on-blue message instead:
/// return Container(
/// alignment: Alignment.center,
/// child: Text(
/// 'Error!',
/// style: TextStyle(color: Colors.yellow),
/// textDirection: TextDirection.ltr,
/// ),
/// );
/// };
/// // Here we would normally runApp() the root widget, but to demonstrate
/// // the error handling we artificially fail:
/// return runApp(Builder(
/// builder: (BuildContext context) {
/// throw 'oh no, an error';
/// },
/// ));
/// }
/// ```
/// {@end-tool}
///
/// See also:
///
/// * [FlutterError.onError], which can be set to a method that exits the
/// application if that is preferable to showing an error message.
/// * <https://flutter.dev/docs/testing/errors>, more information about error
/// handling in Flutter.
class ErrorWidget extends LeafRenderObjectWidget {
/// Creates a widget that displays the given error message.
/// Creates a widget that displays the given exception.
///
/// The message will be the stringification of the given exception, unless
/// computing that value itself throws an exception, in which case it will
/// be the string "Error".
///
/// If this object is inspected from an IDE or the devtools, and the original
/// exception is a [FlutterError] object, the original exception itself will
/// be shown in the inspection output.
ErrorWidget(Object exception)
: message = _stringify(exception),
_flutterError = exception is FlutterError ? exception : null,
super(key: UniqueKey());
/// Creates a widget that displays the given error message.
///
/// An explicit [FlutterError] can be provided to be reported to inspection
/// tools. It need not match the message.
ErrorWidget.withDetails({ this.message = '', FlutterError error })
: _flutterError = error,
super(key: UniqueKey());
/// The configurable factory for [ErrorWidget].
///
/// When an error occurs while building a widget, the broken widget is
@ -3835,17 +3893,28 @@ class ErrorWidget extends LeafRenderObjectWidget {
/// corresponds to a [RenderBox] that can handle the most absurd of incoming
/// constraints. The default constructor maps to a [RenderErrorBox].
///
/// The default behavior is to show the exception's message in debug mode,
/// and to show nothing but a gray background in release builds.
///
/// See also:
///
/// * [FlutterError.onError], which is typically called with the same
/// [FlutterErrorDetails] object immediately prior to this callback being
/// invoked, and which can also be configured to control how errors are
/// reported.
static ErrorWidgetBuilder builder = (FlutterErrorDetails details) => ErrorWidget(details.exception);
/// * <https://flutter.dev/docs/testing/errors>, more information about error
/// handling in Flutter.
static ErrorWidgetBuilder builder = _defaultErrorWidgetBuilder;
/// The message to display.
final String message;
final FlutterError _flutterError;
static Widget _defaultErrorWidgetBuilder(FlutterErrorDetails details) {
String message = '';
assert(() {
message = _stringify(details.exception) + '\nSee also: https://flutter.dev/docs/testing/errors';
return true;
}());
final Object exception = details.exception;
return ErrorWidget.withDetails(message: message, error: exception is FlutterError ? exception : null);
}
static String _stringify(Object exception) {
try {
@ -3856,6 +3925,10 @@ class ErrorWidget extends LeafRenderObjectWidget {
return 'Error';
}
/// The message to display.
final String message;
final FlutterError _flutterError;
@override
RenderBox createRenderObject(BuildContext context) => RenderErrorBox(message);

40
packages/flutter/test/rendering/error_test.dart
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@ -14,9 +14,45 @@ void main() {
testWidgets('test draw error paragraph', (WidgetTester tester) async {
await tester.pumpWidget(ErrorWidget(Exception(errorMessage)));
expect(find.byType(ErrorWidget), paints
..rect(rect: const Rect.fromLTWH(0.0, 0.0, 800.0, 600.0))
..paragraph(offset: Offset.zero));
..paragraph(offset: const Offset(64.0, 96.0)));
final Widget _error = Builder(builder: (BuildContext context) => throw 'pillow');
await tester.pumpWidget(Center(child: SizedBox(width: 100.0, child: _error)));
expect(tester.takeException(), 'pillow');
expect(find.byType(ErrorWidget), paints
..rect(rect: const Rect.fromLTWH(0.0, 0.0, 100.0, 600.0))
..paragraph(offset: const Offset(0.0, 96.0)));
await tester.pumpWidget(Center(child: SizedBox(height: 100.0, child: _error)));
expect(tester.takeException(), null);
await tester.pumpWidget(Center(child: SizedBox(key: UniqueKey(), height: 100.0, child: _error)));
expect(tester.takeException(), 'pillow');
expect(find.byType(ErrorWidget), paints
..rect(rect: const Rect.fromLTWH(0.0, 0.0, 800.0, 100.0))
..paragraph(offset: const Offset(64.0, 0.0)));
RenderErrorBox.minimumWidth = 800.0;
await tester.pumpWidget(Center(child: _error));
expect(tester.takeException(), 'pillow');
expect(find.byType(ErrorWidget), paints
..rect(rect: const Rect.fromLTWH(0.0, 0.0, 800.0, 600.0))
..paragraph(offset: const Offset(0.0, 96.0)));
await tester.pumpWidget(Center(child: _error));
expect(tester.takeException(), null);
expect(find.byType(ErrorWidget), paints
..rect(color: const Color(0xF0900000))
..paragraph());
RenderErrorBox.backgroundColor = const Color(0xFF112233);
await tester.pumpWidget(Center(child: _error));
expect(tester.takeException(), null);
expect(find.byType(ErrorWidget), paints
..rect(color: const Color(0xFF112233))
..paragraph());
});
}

21
packages/flutter/test/widgets/error_widget_builder_test.dart
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@ -5,6 +5,8 @@
import 'package:flutter_test/flutter_test.dart';
import 'package:flutter/widgets.dart';
import '../rendering/mock_canvas.dart';
void main() {
testWidgets('ErrorWidget.builder', (WidgetTester tester) async {
final ErrorWidgetBuilder oldBuilder = ErrorWidget.builder;
@ -24,4 +26,23 @@ void main() {
expect(find.text('oopsie!'), findsOneWidget);
ErrorWidget.builder = oldBuilder;
});
testWidgets('ErrorWidget.builder', (WidgetTester tester) async {
final ErrorWidgetBuilder oldBuilder = ErrorWidget.builder;
ErrorWidget.builder = (FlutterErrorDetails details) {
return ErrorWidget('');
};
await tester.pumpWidget(
SizedBox(
child: Builder(
builder: (BuildContext context) {
throw 'test';
},
),
),
);
expect(tester.takeException().toString(), 'test');
expect(find.byType(ErrorWidget), isNot(paints..paragraph()));
ErrorWidget.builder = oldBuilder;
});
}