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// Copyright 2014 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 'dart:collection';
import 'dart:developer' show Timeline; // to disambiguate reference in dartdocs below
import 'package:flute/foundation.dart';
import 'basic.dart';
import 'framework.dart';
import 'localizations.dart';
import 'lookup_boundary.dart';
import 'media_query.dart';
import 'overlay.dart';
import 'table.dart';
// Examples can assume:
// late BuildContext context;
// List<Widget> children = <Widget>[];
// List<Widget> items = <Widget>[];
// Any changes to this file should be reflected in the debugAssertAllWidgetVarsUnset()
// function below.
/// Log the dirty widgets that are built each frame.
///
/// Combined with [debugPrintBuildScope] or [debugPrintBeginFrameBanner], this
/// allows you to distinguish builds triggered by the initial mounting of a
/// widget tree (e.g. in a call to [runApp]) from the regular builds triggered
/// by the pipeline.
///
/// Combined with [debugPrintScheduleBuildForStacks], this lets you watch a
/// widget's dirty/clean lifecycle.
///
/// To get similar information but showing it on the timeline available from
/// Flutter DevTools rather than getting it in the console (where it can be
/// overwhelming), consider [debugProfileBuildsEnabled].
///
/// See also:
///
/// * [WidgetsBinding.drawFrame], which pumps the build and rendering pipeline
/// to generate a frame.
bool debugPrintRebuildDirtyWidgets = false;
/// Signature for [debugOnRebuildDirtyWidget] implementations.
typedef RebuildDirtyWidgetCallback = void Function(Element e, bool builtOnce);
/// Callback invoked for every dirty widget built each frame.
///
/// This callback is only invoked in debug builds.
///
/// See also:
///
/// * [debugPrintRebuildDirtyWidgets], which does something similar but logs
/// to the console instead of invoking a callback.
/// * [debugOnProfilePaint], which does something similar for [RenderObject]
/// painting.
/// * [WidgetInspectorService], which uses the [debugOnRebuildDirtyWidget]
/// callback to generate aggregate profile statistics describing which widget
/// rebuilds occurred when the
/// `ext.flutter.inspector.trackRebuildDirtyWidgets` service extension is
/// enabled.
RebuildDirtyWidgetCallback? debugOnRebuildDirtyWidget;
/// Log all calls to [BuildOwner.buildScope].
///
/// Combined with [debugPrintScheduleBuildForStacks], this allows you to track
/// when a [State.setState] call gets serviced.
///
/// Combined with [debugPrintRebuildDirtyWidgets] or
/// [debugPrintBeginFrameBanner], this allows you to distinguish builds
/// triggered by the initial mounting of a widget tree (e.g. in a call to
/// [runApp]) from the regular builds triggered by the pipeline.
///
/// See also:
///
/// * [WidgetsBinding.drawFrame], which pumps the build and rendering pipeline
/// to generate a frame.
bool debugPrintBuildScope = false;
/// Log the call stacks that mark widgets as needing to be rebuilt.
///
/// This is called whenever [BuildOwner.scheduleBuildFor] adds an element to the
/// dirty list. Typically this is as a result of [Element.markNeedsBuild] being
/// called, which itself is usually a result of [State.setState] being called.
///
/// To see when a widget is rebuilt, see [debugPrintRebuildDirtyWidgets].
///
/// To see when the dirty list is flushed, see [debugPrintBuildScope].
///
/// To see when a frame is scheduled, see [debugPrintScheduleFrameStacks].
bool debugPrintScheduleBuildForStacks = false;
/// Log when widgets with global keys are deactivated and log when they are
/// reactivated (retaken).
///
/// This can help track down framework bugs relating to the [GlobalKey] logic.
bool debugPrintGlobalKeyedWidgetLifecycle = false;
/// Adds [Timeline] events for every Widget built.
///
/// The timing information this flag exposes is not representative of the actual
/// cost of building, because the overhead of adding timeline events is
/// significant relative to the time each object takes to build. However, it can
/// expose unexpected widget behavior in the timeline.
///
/// In debug builds, additional information is included in the trace (such as
/// the properties of widgets being built). Collecting this data is
/// expensive and further makes these traces non-representative of actual
/// performance. This data is omitted in profile builds.
///
/// For more information about performance debugging in Flutter, see
/// <https://flutter.dev/docs/perf/rendering>.
///
/// See also:
///
/// * [debugPrintRebuildDirtyWidgets], which does something similar but
/// reporting the builds to the console.
/// * [debugProfileLayoutsEnabled], which does something similar for layout,
/// and [debugPrintLayouts], its console equivalent.
/// * [debugProfilePaintsEnabled], which does something similar for painting.
/// * [debugProfileBuildsEnabledUserWidgets], which adds events for user-created
/// [Widget] build times and incurs less overhead.
/// * [debugEnhanceBuildTimelineArguments], which enhances the trace with
/// debugging information related to [Widget] builds.
bool debugProfileBuildsEnabled = false;
/// Adds [Timeline] events for every user-created [Widget] built.
///
/// A user-created [Widget] is any [Widget] that is constructed in the root
/// library. Often [Widget]s contain child [Widget]s that are constructed in
/// libraries (for example, a [TextButton] having a [RichText] child). Timeline
/// events for those children will be omitted with this flag. This works for any
/// [Widget] not just ones declared in the root library.
///
/// See also:
///
/// * [debugProfileBuildsEnabled], which functions similarly but shows events
/// for every widget and has a higher overhead cost.
/// * [debugEnhanceBuildTimelineArguments], which enhances the trace with
/// debugging information related to [Widget] builds.
bool debugProfileBuildsEnabledUserWidgets = false;
/// Adds debugging information to [Timeline] events related to [Widget] builds.
///
/// This flag will only add [Timeline] event arguments for debug builds.
/// Additional arguments will be added for the "BUILD" [Timeline] event and for
/// all [Widget] build [Timeline] events, which are the [Timeline] events that
/// are added when either of [debugProfileBuildsEnabled] and
/// [debugProfileBuildsEnabledUserWidgets] are true. The debugging information
/// that will be added in trace arguments includes stats around [Widget] dirty
/// states and [Widget] diagnostic information (i.e. [Widget] properties).
///
/// See also:
///
/// * [debugProfileBuildsEnabled], which adds [Timeline] events for every
/// [Widget] built.
/// * [debugProfileBuildsEnabledUserWidgets], which adds [Timeline] events for
/// every user-created [Widget] built.
/// * [debugEnhanceLayoutTimelineArguments], which does something similar for
/// events related to [RenderObject] layouts.
/// * [debugEnhancePaintTimelineArguments], which does something similar for
/// events related to [RenderObject] paints.
bool debugEnhanceBuildTimelineArguments = false;
/// Show banners for deprecated widgets.
bool debugHighlightDeprecatedWidgets = false;
Key? _firstNonUniqueKey(Iterable<Widget> widgets) {
final Set<Key> keySet = HashSet<Key>();
for (final Widget widget in widgets) {
if (widget.key == null) {
continue;
}
if (!keySet.add(widget.key!)) {
return widget.key;
}
}
return null;
}
/// Asserts if the given child list contains any duplicate non-null keys.
///
/// To invoke this function, use the following pattern:
///
/// ```dart
/// class MyWidget extends StatelessWidget {
/// MyWidget({ super.key, required this.children }) {
/// assert(!debugChildrenHaveDuplicateKeys(this, children));
/// }
///
/// final List<Widget> children;
///
/// // ...
/// }
/// ```
///
/// If specified, the `message` overrides the default message.
///
/// For a version of this function that can be used in contexts where
/// the list of items does not have a particular parent, see
/// [debugItemsHaveDuplicateKeys].
///
/// Does nothing if asserts are disabled. Always returns false.
bool debugChildrenHaveDuplicateKeys(Widget parent, Iterable<Widget> children, { String? message }) {
assert(() {
final Key? nonUniqueKey = _firstNonUniqueKey(children);
if (nonUniqueKey != null) {
throw FlutterError(
"${message ?? 'Duplicate keys found.\n'
'If multiple keyed widgets exist as children of another widget, they must have unique keys.'}"
'\n$parent has multiple children with key $nonUniqueKey.',
);
}
return true;
}());
return false;
}
/// Asserts if the given list of items contains any duplicate non-null keys.
///
/// To invoke this function, use the following pattern:
///
/// ```dart
/// assert(!debugItemsHaveDuplicateKeys(items));
/// ```
///
/// For a version of this function specifically intended for parents
/// checking their children lists, see [debugChildrenHaveDuplicateKeys].
///
/// Does nothing if asserts are disabled. Always returns false.
bool debugItemsHaveDuplicateKeys(Iterable<Widget> items) {
assert(() {
final Key? nonUniqueKey = _firstNonUniqueKey(items);
if (nonUniqueKey != null) {
throw FlutterError('Duplicate key found: $nonUniqueKey.');
}
return true;
}());
return false;
}
/// Asserts that the given context has a [Table] ancestor.
///
/// Used by [TableRowInkWell] to make sure that it is only used in an appropriate context.
///
/// To invoke this function, use the following pattern, typically in the
/// relevant Widget's build method:
///
/// ```dart
/// assert(debugCheckHasTable(context));
/// ```
///
/// Always place this before any early returns, so that the invariant is checked
/// in all cases. This prevents bugs from hiding until a particular codepath is
/// hit.
///
/// This method can be expensive (it walks the element tree).
///
/// Does nothing if asserts are disabled. Always returns true.
bool debugCheckHasTable(BuildContext context) {
assert(() {
if (context.widget is! Table && context.findAncestorWidgetOfExactType<Table>() == null) {
throw FlutterError.fromParts(<DiagnosticsNode>[
ErrorSummary('No Table widget found.'),
ErrorDescription('${context.widget.runtimeType} widgets require a Table widget ancestor.'),
context.describeWidget('The specific widget that could not find a Table ancestor was'),
context.describeOwnershipChain('The ownership chain for the affected widget is'),
]);
}
return true;
}());
return true;
}
/// Asserts that the given context has a [MediaQuery] ancestor.
///
/// Used by various widgets to make sure that they are only used in an
/// appropriate context.
///
/// To invoke this function, use the following pattern, typically in the
/// relevant Widget's build method:
///
/// ```dart
/// assert(debugCheckHasMediaQuery(context));
/// ```
///
/// Always place this before any early returns, so that the invariant is checked
/// in all cases. This prevents bugs from hiding until a particular codepath is
/// hit.
///
/// Does nothing if asserts are disabled. Always returns true.
bool debugCheckHasMediaQuery(BuildContext context) {
assert(() {
if (context.widget is! MediaQuery && context.getElementForInheritedWidgetOfExactType<MediaQuery>() == null) {
throw FlutterError.fromParts(<DiagnosticsNode>[
ErrorSummary('No MediaQuery widget ancestor found.'),
ErrorDescription('${context.widget.runtimeType} widgets require a MediaQuery widget ancestor.'),
context.describeWidget('The specific widget that could not find a MediaQuery ancestor was'),
context.describeOwnershipChain('The ownership chain for the affected widget is'),
ErrorHint(
'No MediaQuery ancestor could be found starting from the context '
'that was passed to MediaQuery.of(). This can happen because you '
'have not added a WidgetsApp, CupertinoApp, or MaterialApp widget '
'(those widgets introduce a MediaQuery), or it can happen if the '
'context you use comes from a widget above those widgets.',
),
]);
}
return true;
}());
return true;
}
/// Asserts that the given context has a [Directionality] ancestor.
///
/// Used by various widgets to make sure that they are only used in an
/// appropriate context.
///
/// To invoke this function, use the following pattern, typically in the
/// relevant Widget's build method:
///
/// ```dart
/// assert(debugCheckHasDirectionality(context));
/// ```
///
/// To improve the error messages you can add some extra color using the
/// named arguments.
///
/// * why: explain why the direction is needed, for example "to resolve
/// the 'alignment' argument". Should be an adverb phrase describing why.
/// * hint: explain why this might be happening, for example "The default
/// value of the 'alignment' argument of the $runtimeType widget is an
/// AlignmentDirectional value.". Should be a fully punctuated sentence.
/// * alternative: provide additional advice specific to the situation,
/// especially an alternative to providing a Directionality ancestor.
/// For example, "Alternatively, consider specifying the 'textDirection'
/// argument.". Should be a fully punctuated sentence.
///
/// Each one can be null, in which case it is skipped (this is the default).
/// If they are non-null, they are included in the order above, interspersed
/// with the more generic advice regarding [Directionality].
///
/// Always place this before any early returns, so that the invariant is checked
/// in all cases. This prevents bugs from hiding until a particular codepath is
/// hit.
///
/// Does nothing if asserts are disabled. Always returns true.
bool debugCheckHasDirectionality(BuildContext context, { String? why, String? hint, String? alternative }) {
assert(() {
if (context.widget is! Directionality && context.getElementForInheritedWidgetOfExactType<Directionality>() == null) {
why = why == null ? '' : ' $why';
throw FlutterError.fromParts(<DiagnosticsNode>[
ErrorSummary('No Directionality widget found.'),
ErrorDescription('${context.widget.runtimeType} widgets require a Directionality widget ancestor$why.\n'),
if (hint != null)
ErrorHint(hint),
context.describeWidget('The specific widget that could not find a Directionality ancestor was'),
context.describeOwnershipChain('The ownership chain for the affected widget is'),
ErrorHint(
'Typically, the Directionality widget is introduced by the MaterialApp '
'or WidgetsApp widget at the top of your application widget tree. It '
'determines the ambient reading direction and is used, for example, to '
'determine how to lay out text, how to interpret "start" and "end" '
'values, and to resolve EdgeInsetsDirectional, '
'AlignmentDirectional, and other *Directional objects.',
),
if (alternative != null)
ErrorHint(alternative),
]);
}
return true;
}());
return true;
}
/// Asserts that the `built` widget is not null.
///
/// Used when the given `widget` calls a builder function to check that the
/// function returned a non-null value, as typically required.
///
/// Does nothing when asserts are disabled.
void debugWidgetBuilderValue(Widget widget, Widget? built) {
assert(() {
if (built == null) {
throw FlutterError.fromParts(<DiagnosticsNode>[
ErrorSummary('A build function returned null.'),
DiagnosticsProperty<Widget>('The offending widget is', widget, style: DiagnosticsTreeStyle.errorProperty),
ErrorDescription('Build functions must never return null.'),
ErrorHint(
'To return an empty space that causes the building widget to fill available room, return "Container()". '
'To return an empty space that takes as little room as possible, return "Container(width: 0.0, height: 0.0)".',
),
]);
}
if (widget == built) {
throw FlutterError.fromParts(<DiagnosticsNode>[
ErrorSummary('A build function returned context.widget.'),
DiagnosticsProperty<Widget>('The offending widget is', widget, style: DiagnosticsTreeStyle.errorProperty),
ErrorDescription(
'Build functions must never return their BuildContext parameter\'s widget or a child that contains "context.widget". '
'Doing so introduces a loop in the widget tree that can cause the app to crash.',
),
]);
}
return true;
}());
}
/// Asserts that the given context has a [Localizations] ancestor that contains
/// a [WidgetsLocalizations] delegate.
///
/// To call this function, use the following pattern, typically in the
/// relevant Widget's build method:
///
/// ```dart
/// assert(debugCheckHasWidgetsLocalizations(context));
/// ```
///
/// Always place this before any early returns, so that the invariant is checked
/// in all cases. This prevents bugs from hiding until a particular codepath is
/// hit.
///
/// Does nothing if asserts are disabled. Always returns true.
bool debugCheckHasWidgetsLocalizations(BuildContext context) {
assert(() {
if (Localizations.of<WidgetsLocalizations>(context, WidgetsLocalizations) == null) {
throw FlutterError.fromParts(<DiagnosticsNode>[
ErrorSummary('No WidgetsLocalizations found.'),
ErrorDescription(
'${context.widget.runtimeType} widgets require WidgetsLocalizations '
'to be provided by a Localizations widget ancestor.',
),
ErrorDescription(
'The widgets library uses Localizations to generate messages, '
'labels, and abbreviations.',
),
ErrorHint(
'To introduce a WidgetsLocalizations, either use a '
'WidgetsApp at the root of your application to include them '
'automatically, or add a Localization widget with a '
'WidgetsLocalizations delegate.',
),
...context.describeMissingAncestor(expectedAncestorType: WidgetsLocalizations),
]);
}
return true;
}());
return true;
}
/// Asserts that the given context has an [Overlay] ancestor.
///
/// To call this function, use the following pattern, typically in the
/// relevant Widget's build method:
///
/// ```dart
/// assert(debugCheckHasOverlay(context));
/// ```
///
/// Always place this before any early returns, so that the invariant is checked
/// in all cases. This prevents bugs from hiding until a particular codepath is
/// hit.
///
/// This method can be expensive (it walks the element tree).
///
/// Does nothing if asserts are disabled. Always returns true.
bool debugCheckHasOverlay(BuildContext context) {
assert(() {
if (LookupBoundary.findAncestorWidgetOfExactType<Overlay>(context) == null) {
final bool hiddenByBoundary = LookupBoundary.debugIsHidingAncestorWidgetOfExactType<Overlay>(context);
throw FlutterError.fromParts(<DiagnosticsNode>[
ErrorSummary('No Overlay widget found${hiddenByBoundary ? ' within the closest LookupBoundary' : ''}.'),
if (hiddenByBoundary)
ErrorDescription(
'There is an ancestor Overlay widget, but it is hidden by a LookupBoundary.'
),
ErrorDescription(
'${context.widget.runtimeType} widgets require an Overlay '
'widget ancestor within the closest LookupBoundary.\n'
'An overlay lets widgets float on top of other widget children.',
),
ErrorHint(
'To introduce an Overlay widget, you can either directly '
'include one, or use a widget that contains an Overlay itself, '
'such as a Navigator, WidgetApp, MaterialApp, or CupertinoApp.',
),
...context.describeMissingAncestor(expectedAncestorType: Overlay),
]);
}
return true;
}());
return true;
}
/// Returns true if none of the widget library debug variables have been changed.
///
/// This function is used by the test framework to ensure that debug variables
/// haven't been inadvertently changed.
///
/// See [the widgets library](widgets/widgets-library.html) for a complete list.
bool debugAssertAllWidgetVarsUnset(String reason) {
assert(() {
if (debugPrintRebuildDirtyWidgets ||
debugPrintBuildScope ||
debugPrintScheduleBuildForStacks ||
debugPrintGlobalKeyedWidgetLifecycle ||
debugProfileBuildsEnabled ||
debugHighlightDeprecatedWidgets ||
debugProfileBuildsEnabledUserWidgets) {
throw FlutterError(reason);
}
return true;
}());
return true;
}