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AsyncSnapshot.data to throw if error or no data (#34626)

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This updates `AsyncSnapshot.data` to act as `AsyncSnapshot.requireData`
used to -- and it removes `AsyncSnapshot.requireData`. Correspondingly,
this adds a `StreamBuilder.withoutInitialData()` constructor, makes the
`initialData` argument to the default `StreamBuilder()` constructor required,
and deprecates the `initialData` argument to the `FutureBuilder()` constructor.

See the  breaking change announcement for more info.

https://github.com/flutter/flutter/issues/34545
https://groups.google.com/forum/#!topic/flutter-announce/H6Od0QdsdrI
This commit is contained in:
Todd Volkert 2019-07-18 16:26:13 -07:00 committed by GitHub
parent 1aa4628fa2
commit b61fcfd25d
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2 changed files with 442 additions and 185 deletions
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370
packages/flutter/lib/src/widgets/async.dart
View File

@ -59,35 +59,41 @@ abstract class StreamBuilderBase<T, S> extends StatefulWidget {
///
/// Sub-classes must override this method to provide the initial value for
/// the fold computation.
@protected
S initial();
/// Returns an updated version of the [current] summary reflecting that we
/// are now connected to a stream.
///
/// The default implementation returns [current] as is.
@protected
S afterConnected(S current) => current;
/// Returns an updated version of the [current] summary following a data event.
///
/// Sub-classes must override this method to specify how the current summary
/// is combined with the new data item in the fold computation.
@protected
S afterData(S current, T data);
/// Returns an updated version of the [current] summary following an error.
///
/// The default implementation returns [current] as is.
@protected
S afterError(S current, Object error) => current;
/// Returns an updated version of the [current] summary following stream
/// termination.
///
/// The default implementation returns [current] as is.
@protected
S afterDone(S current) => current;
/// Returns an updated version of the [current] summary reflecting that we
/// are no longer connected to a stream.
///
/// The default implementation returns [current] as is.
@protected
S afterDisconnected(S current) => current;
/// Returns a Widget based on the [currentSummary].
@ -185,6 +191,8 @@ enum ConnectionState {
/// Immutable representation of the most recent interaction with an asynchronous
/// computation.
///
/// `T` is the type of computation data.
///
/// See also:
///
/// * [StreamBuilder], which builds itself based on a snapshot from interacting
@ -193,46 +201,68 @@ enum ConnectionState {
/// with a [Future].
@immutable
class AsyncSnapshot<T> {
/// Creates an [AsyncSnapshot] with the specified [connectionState],
/// and optionally either [data] or [error] (but not both).
const AsyncSnapshot._(this.connectionState, this.data, this.error)
/// Creates an [AsyncSnapshot] with the specified [connectionState] and
/// [hasData], and optionally either [data] or [error] (but not both).
///
/// It is legal for both [hasData] to be true and [data] to be null.
const AsyncSnapshot._(this.connectionState, this.hasData, this._data, this.error)
: assert(connectionState != null),
assert(!(data != null && error != null));
assert(hasData != null),
assert(hasData || _data == null),
assert(!(hasData && error != null));
/// Creates an [AsyncSnapshot] in [ConnectionState.none] with null data and error.
const AsyncSnapshot.nothing() : this._(ConnectionState.none, null, null);
/// Creates an [AsyncSnapshot] in the specified [state] and with neither
/// [data] nor [error].
const AsyncSnapshot.withoutData(ConnectionState state) : this._(state, false, null, null);
/// Creates an [AsyncSnapshot] in the specified [state] and with the specified [data].
const AsyncSnapshot.withData(ConnectionState state, T data) : this._(state, data, null);
/// Creates an [AsyncSnapshot] in the specified [state] and with the
/// specified [data] (possibly null).
const AsyncSnapshot.withData(ConnectionState state, T data) : this._(state, true, data, null);
/// Creates an [AsyncSnapshot] in the specified [state] and with the specified [error].
const AsyncSnapshot.withError(ConnectionState state, Object error) : this._(state, null, error);
/// Creates an [AsyncSnapshot] in the specified `state` and with the
/// specified [error].
const AsyncSnapshot.withError(ConnectionState state, Object error) : this._(state, false, null, error);
/// Current state of connection to the asynchronous computation.
/// The current state of the connection to the asynchronous computation.
///
/// This property exists independently of the [data] and [error] properties.
/// In other words, a snapshot can exist with any combination of
/// (`connectionState`/`data`) or (`connectionState`/`error`) tuples.
///
/// This is guaranteed to be non-null.
final ConnectionState connectionState;
/// The latest data received by the asynchronous computation.
/// Whether this snapshot contains [data].
///
/// If this is non-null, [hasData] will be true.
/// This can be false even when the asynchronous computation has completed
/// successfully ([connectionState] is [ConnectionState.done]), if the
/// computation did not return a value. For example, a [Future<void>] will
/// complete with no data even if it completes successfully.
///
/// If [error] is not null, this will be null. See [hasError].
///
/// If the asynchronous computation has never returned a value, this may be
/// set to an initial data value specified by the relevant widget. See
/// [FutureBuilder.initialData] and [StreamBuilder.initialData].
final T data;
/// If this property is false, then attempting to access the [data] property
/// will throw an exception.
final bool hasData;
/// Returns latest data received, failing if there is no data.
/// The latest data received by the asynchronous computation, failing if
/// there is no data.
///
/// Throws [error], if [hasError]. Throws [StateError], if neither [hasData]
/// nor [hasError].
T get requireData {
/// If [hasData] is true, accessing this property will not throw an error.
///
/// If [error] is not null, attempting to access this property will throw
/// [error]. See [hasError].
///
/// If neither [hasData] nor [hasError] is true, then accessing this
/// property will throw a [StateError].
T get data {
if (hasData)
return data;
if (hasError)
return _data;
if (hasError) {
// TODO(tvolkert): preserve the stack trace (https://github.com/dart-lang/sdk/issues/30741)
throw error;
}
throw StateError('Snapshot has neither data nor error');
}
final T _data;
/// The latest error object received by the asynchronous computation.
///
@ -243,41 +273,46 @@ class AsyncSnapshot<T> {
/// Returns a snapshot like this one, but in the specified [state].
///
/// The [data] and [error] fields persist unmodified, even if the new state is
/// [ConnectionState.none].
AsyncSnapshot<T> inState(ConnectionState state) => AsyncSnapshot<T>._(state, data, error);
/// Returns whether this snapshot contains a non-null [data] value.
///
/// This can be false even when the asynchronous computation has completed
/// successfully, if the computation did not return a non-null value. For
/// example, a [Future<void>] will complete with the null value even if it
/// completes successfully.
bool get hasData => data != null;
/// The [hasData], [data], [hasError], and [error] fields persist unmodified,
/// even if the new state is [ConnectionState.none].
AsyncSnapshot<T> inState(ConnectionState state) => AsyncSnapshot<T>._(state, hasData, _data, error);
/// Returns whether this snapshot contains a non-null [error] value.
///
/// This is always true if the asynchronous computation's last result was
/// failure.
///
/// When this is true, [hasData] will always be false.
bool get hasError => error != null;
@override
String toString() => '$runtimeType($connectionState, $data, $error)';
String toString() {
final StringBuffer buffer = StringBuffer()..write('$runtimeType')
..write('(')
..write('$connectionState');
if (hasData)
buffer.write(', data: $_data');
else if (hasError)
buffer.write(', error: $error');
buffer.write(')');
return buffer.toString();
}
@override
bool operator ==(dynamic other) {
if (identical(this, other))
return true;
if (other is! AsyncSnapshot<T>)
if (runtimeType != other.runtimeType)
return false;
final AsyncSnapshot<T> typedOther = other;
return connectionState == typedOther.connectionState
&& data == typedOther.data
&& hasData == typedOther.hasData
&& _data == typedOther._data
&& error == typedOther.error;
}
@override
int get hashCode => hashValues(connectionState, data, error);
int get hashCode => hashValues(connectionState, hasData, _data, error);
}
/// Signature for strategies that build widgets based on asynchronous
@ -307,12 +342,12 @@ typedef AsyncWidgetBuilder<T> = Widget Function(BuildContext context, AsyncSnaps
/// of the following snapshots that includes the last one (the one with
/// ConnectionState.done):
///
/// * `new AsyncSnapshot<int>.withData(ConnectionState.waiting, null)`
/// * `new AsyncSnapshot<int>.withData(ConnectionState.active, 0)`
/// * `new AsyncSnapshot<int>.withData(ConnectionState.active, 1)`
/// * `AsyncSnapshot<int>.withData(ConnectionState.waiting, null)`
/// * `AsyncSnapshot<int>.withData(ConnectionState.active, 0)`
/// * `AsyncSnapshot<int>.withData(ConnectionState.active, 1)`
/// * ...
/// * `new AsyncSnapshot<int>.withData(ConnectionState.active, 9)`
/// * `new AsyncSnapshot<int>.withData(ConnectionState.done, 9)`
/// * `AsyncSnapshot<int>.withData(ConnectionState.active, 9)`
/// * `AsyncSnapshot<int>.withData(ConnectionState.done, 9)`
///
/// The actual sequence of invocations of the [builder] depends on the relative
/// timing of events produced by the stream and the build rate of the Flutter
@ -329,7 +364,7 @@ typedef AsyncWidgetBuilder<T> = Widget Function(BuildContext context, AsyncSnaps
///
/// The stream may produce errors, resulting in snapshots of the form:
///
/// * `new AsyncSnapshot<int>.withError(ConnectionState.active, 'some error')`
/// * `AsyncSnapshot<int>.withError(ConnectionState.active, 'some error')`
///
/// The data and error fields of snapshots produced are only changed when the
/// state is `ConnectionState.active`.
@ -337,7 +372,20 @@ typedef AsyncWidgetBuilder<T> = Widget Function(BuildContext context, AsyncSnaps
/// The initial snapshot data can be controlled by specifying [initialData].
/// This should be used to ensure that the first frame has the expected value,
/// as the builder will always be called before the stream listener has a chance
/// to be processed.
/// to be processed. In cases where callers wish to have no initial data, the
/// [new StreamBuilder.withoutInitialData] constructor may be used. Doing so
/// may cause the first frame to have a snapshot that contains no data.
///
/// ## Void StreamBuilders
///
/// The `StreamBuilder<void>` type will produce snapshots that contain no data.
/// An example stream of snapshots would be the following:
///
/// * `AsyncSnapshot<void>.withoutData(ConnectionState.waiting)`
/// * `AsyncSnapshot<void>.withoutData(ConnectionState.active)`
/// * ...
/// * `AsyncSnapshot<void>.withoutData(ConnectionState.active)`
/// * `AsyncSnapshot<void>.withoutData(ConnectionState.done)`
///
/// {@tool sample}
///
@ -348,6 +396,7 @@ typedef AsyncWidgetBuilder<T> = Widget Function(BuildContext context, AsyncSnaps
/// ```dart
/// StreamBuilder<int>(
/// stream: _lot?.bids, // a Stream<int> or null
/// initialData: 100, // initial seed value
/// builder: (BuildContext context, AsyncSnapshot<int> snapshot) {
/// if (snapshot.hasError)
/// return Text('Error: ${snapshot.error}');
@ -372,42 +421,95 @@ typedef AsyncWidgetBuilder<T> = Widget Function(BuildContext context, AsyncSnaps
// TODO(ianh): remove unreachable code above once https://github.com/dart-lang/linter/issues/1139 is fixed
class StreamBuilder<T> extends StreamBuilderBase<T, AsyncSnapshot<T>> {
/// Creates a new [StreamBuilder] that builds itself based on the latest
/// snapshot of interaction with the specified [stream] and whose build
/// snapshot of interaction with the specified `stream` and whose build
/// strategy is given by [builder].
///
/// The [initialData] is used to create the initial snapshot.
/// The [initialData] argument is used to create the initial snapshot. For
/// cases where there is no initial snapshot or the initial snapshot is not
/// yet available, callers may construct a [StreamBuilder] without an initial
/// snapshot using [new StreamBuilder.withoutInitialData].
///
/// The [builder] must not be null.
const StreamBuilder({
Key key,
this.initialData,
@required T initialData,
Stream<T> stream,
@required this.builder,
}) : assert(builder != null),
hasInitialData = true,
_initialData = initialData,
super(key: key, stream: stream);
/// Creates a new [StreamBuilder] that builds itself based on the latest
/// snapshot of interaction with the specified `stream` and whose build
/// strategy is given by [builder].
///
/// The initial snapshot will contain no data.
///
/// The [builder] must not be null.
const StreamBuilder.withoutInitialData({
Key key,
Stream<T> stream,
@required this.builder,
}) : assert(builder != null),
hasInitialData = false,
_initialData = null,
super(key: key, stream: stream);
/// The build strategy currently used by this builder.
final AsyncWidgetBuilder<T> builder;
/// Whether this builder's initial snapshot contains data.
///
/// If this is false, then attempting to access [initialData] will throw an
/// error.
///
/// See also:
///
/// * [AsyncSnapshot.hasData], the corresponding property that will be set
/// in the initial snapshot.
final bool hasInitialData;
/// The data that will be used to create the initial snapshot.
///
/// Providing this value (presumably obtained synchronously somehow when the
/// [Stream] was created) ensures that the first frame will show useful data.
/// Otherwise, the first frame will be built with the value null, regardless
/// of whether a value is available on the stream: since streams are
/// asynchronous, no events from the stream can be obtained before the initial
/// build.
final T initialData;
/// Otherwise, the first frame will be built with a snapshot that contains no
/// data, regardless of whether a value is available on the stream: since
/// streams are asynchronous, no events from the stream can be obtained
/// before the initial build.
///
/// Some builders intentionally have no data when first built. For those
/// cases, callers can use the [new StreamBuilder.withoutInitialData]
/// constructor. When a builder was constructed in this way, attempting to
/// access the [initialData] property will throw a [StateError].
T get initialData {
if (!hasInitialData) {
throw StateError(
'StreamBuilder was created without initial data, yet the initialData '
'property was accessed. If you wish your StreamBuilder to have initial '
'data, create it using the default constructor.',
);
}
return _initialData;
}
final T _initialData;
@override
AsyncSnapshot<T> initial() => AsyncSnapshot<T>.withData(ConnectionState.none, initialData);
AsyncSnapshot<T> initial() {
return hasInitialData
? AsyncSnapshot<T>.withData(ConnectionState.none, initialData)
: AsyncSnapshot<T>.withoutData(ConnectionState.none);
}
@override
AsyncSnapshot<T> afterConnected(AsyncSnapshot<T> current) => current.inState(ConnectionState.waiting);
@override
AsyncSnapshot<T> afterData(AsyncSnapshot<T> current, T data) {
return AsyncSnapshot<T>.withData(ConnectionState.active, data);
return _TypeLiteral.isVoidType(T)
? AsyncSnapshot<T>.withoutData(ConnectionState.active)
: AsyncSnapshot<T>.withData(ConnectionState.active, data);
}
@override
@ -455,23 +557,17 @@ class StreamBuilder<T> extends StreamBuilderBase<T, AsyncSnapshot<T>> {
///
/// ## Builder contract
///
/// For a future that completes successfully with data, assuming [initialData]
/// is null, the [builder] will be called with either both or only the latter of
/// the following snapshots:
/// For a future that completes successfully with data, the [builder] will be
/// called with either both or only the latter of the following snapshots:
///
/// * `new AsyncSnapshot<String>.withData(ConnectionState.waiting, null)`
/// * `new AsyncSnapshot<String>.withData(ConnectionState.done, 'some data')`
/// * `AsyncSnapshot<String>.withoutData(ConnectionState.waiting)`
/// * `AsyncSnapshot<String>.withData(ConnectionState.done, 'some data')`
///
/// If that same future instead completed with an error, the [builder] would be
/// called with either both or only the latter of:
///
/// * `new AsyncSnapshot<String>.withData(ConnectionState.waiting, null)`
/// * `new AsyncSnapshot<String>.withError(ConnectionState.done, 'some error')`
///
/// The initial snapshot data can be controlled by specifying [initialData]. You
/// would use this facility to ensure that if the [builder] is invoked before
/// the future completes, the snapshot carries data of your choice rather than
/// the default null value.
/// * `AsyncSnapshot<String>.withoutData(ConnectionState.waiting)`
/// * `AsyncSnapshot<String>.withError(ConnectionState.done, 'some error')`
///
/// The data and error fields of the snapshot change only as the connection
/// state field transitions from `waiting` to `done`, and they will be retained
@ -479,8 +575,8 @@ class StreamBuilder<T> extends StreamBuilderBase<T, AsyncSnapshot<T>> {
/// old future has already completed successfully with data as above, changing
/// configuration to a new future results in snapshot pairs of the form:
///
/// * `new AsyncSnapshot<String>.withData(ConnectionState.none, 'data of first future')`
/// * `new AsyncSnapshot<String>.withData(ConnectionState.waiting, 'data of second future')`
/// * `AsyncSnapshot<String>.withData(ConnectionState.none, 'data of first future')`
/// * `AsyncSnapshot<String>.withData(ConnectionState.waiting, 'data of second future')`
///
/// In general, the latter will be produced only when the new future is
/// non-null, and the former only when the old future is non-null.
@ -489,6 +585,12 @@ class StreamBuilder<T> extends StreamBuilderBase<T, AsyncSnapshot<T>> {
/// `future?.asStream()`, except that snapshots with `ConnectionState.active`
/// may appear for the latter, depending on how the stream is implemented.
///
/// ## Void futures
///
/// The `FutureBuilder<void>` type will produce snapshots that contain no data:
///
/// * `AsyncSnapshot<String>.withoutData(ConnectionState.done)`
///
/// {@tool sample}
///
/// This sample shows a [FutureBuilder] configuring a text label to show the
@ -497,7 +599,13 @@ class StreamBuilder<T> extends StreamBuilderBase<T, AsyncSnapshot<T>> {
///
/// ```dart
/// FutureBuilder<String>(
/// future: _calculation, // a previously-obtained Future<String> or null
/// // A previously-obtained `Future<String>` or null.
/// //
/// // This MUST NOT be created during the call to the `build()` method that
/// // creates the `FutureBuilder`. Doing so will cause a new future to be
/// // instantiated every time `build()` is called (potentially every frame).
/// future: _calculation,
///
/// builder: (BuildContext context, AsyncSnapshot<String> snapshot) {
/// switch (snapshot.connectionState) {
/// case ConnectionState.none:
@ -520,11 +628,33 @@ class FutureBuilder<T> extends StatefulWidget {
/// Creates a widget that builds itself based on the latest snapshot of
/// interaction with a [Future].
///
/// The [builder] must not be null.
/// The [future] argument must have been obtained earlier, e.g. during
/// [State.initState], [State.didUpdateConfig], or
/// [State.didChangeDependencies]. It must not be created during the
/// [State.build] or [StatelessWidget.build] method call when constructing
/// the [FutureBuilder]. If the [future] is created at the same time as the
/// [FutureBuilder], then every time the [FutureBuilder]'s parent is rebuilt,
/// the asynchronous task will be restarted.
///
// ignore: deprecated_member_use_from_same_package
/// The [initialData] argument specifies the data that will be used to create
/// the snapshots provided to [builder] until a non-null [future] has
/// completed. This argument is deprecated and will be removed in a future
/// stable release because snapshots that are provided to the [builder]
/// contain an [AsyncSnapshot.connectionState] property that indicates the
/// state of the [future]. The builder can use that connection state to
/// provide an "initial value" when the future has not yet completed.
///
/// The [builder] argument must not be null.
const FutureBuilder({
Key key,
this.future,
this.initialData,
@Deprecated(
'Instead of providing initialData to FutureBuilder, consider checking '
'for ConnectionState.none or ConnectionState.waiting in your build() '
'method to know whether the future has completed or not.',
)
this.initialData, // ignore: deprecated_member_use_from_same_package
@required this.builder,
}) : assert(builder != null),
super(key: key);
@ -533,7 +663,10 @@ class FutureBuilder<T> extends StatefulWidget {
/// possibly null.
///
/// If no future has yet completed, including in the case where [future] is
/// null, the data provided to the [builder] will be set to [initialData].
// ignore: deprecated_member_use_from_same_package
/// null, the snapshot provided to the [builder] will contain [initialData]
/// if this widget was created with initial data or will contain no data if
/// this widget was created without initial data.
final Future<T> future;
/// The build strategy currently used by this builder.
@ -542,29 +675,56 @@ class FutureBuilder<T> extends StatefulWidget {
/// [AsyncSnapshot.connectionState] property will be one of the following
/// values:
///
/// * [ConnectionState.none]: [future] is null. The [AsyncSnapshot.data] will
/// be set to [initialData], unless a future has previously completed, in
/// which case the previous result persists.
/// * [ConnectionState.none]: [future] is null.
///
/// * [ConnectionState.waiting]: [future] is not null, but has not yet
/// completed. The [AsyncSnapshot.data] will be set to [initialData],
/// unless a future has previously completed, in which case the previous
/// result persists.
/// If this widget was created with initial data (deprecated), then the
/// [AsyncSnapshot.data] will be set to [initialData], unless a future has
/// previously completed, in which case the previous result persists.
///
/// If this widget was created without initial data, then the
/// [AsyncSnapshot.data] will be unset, and attempts to access the data
/// will result in an exception.
///
/// * [ConnectionState.waiting]: [future] is not null but has not yet
/// completed.
///
/// If this widget was created with initial data (deprecated), then the
/// [AsyncSnapshot.data] will be set to [initialData], unless a future has
/// previously completed, in which case the previous result persists.
///
/// If this widget was created without initial data, then the
/// [AsyncSnapshot.data] will be unset, and attempts to access the data
/// will result in an exception.
///
/// * [ConnectionState.done]: [future] is not null, and has completed. If the
/// future completed successfully, the [AsyncSnapshot.data] will be set to
/// the value to which the future completed. If it completed with an error,
/// [AsyncSnapshot.hasError] will be true and [AsyncSnapshot.error] will be
/// set to the error object.
///
/// In the case of [future] being a [Future<void>], the snapshot will not
/// contain data even if the future completed successfully.
final AsyncWidgetBuilder<T> builder;
/// The data that will be used to create the snapshots provided until a
/// non-null [future] has completed.
///
/// If the future completes with an error, the data in the [AsyncSnapshot]
/// provided to the [builder] will become null, regardless of [initialData].
/// (The error itself will be available in [AsyncSnapshot.error], and
/// If the future completes with an error, the [AsyncSnapshot] provided to
/// the [builder] will contain no data, regardless of [initialData]. (The
/// error itself will be available in [AsyncSnapshot.error], and
/// [AsyncSnapshot.hasError] will be true.)
///
/// This field is deprecated and will be removed in a future stable release
/// because snapshots that are provided to the [builder] contain an
/// [AsyncSnapshot.connectionState] property that indicates the state of the
/// [future]. The builder can use that connection state to provide an
/// "initial value" when the future has not yet completed.
@Deprecated(
'Instead of using FutureBuilder.initialData, consider checking '
'for ConnectionState.none or ConnectionState.waiting in your build() '
'ConnectionState.none or ConnectionState.waiting in your build() '
'method to know whether the future has completed or not.',
)
final T initialData;
@override
@ -582,7 +742,11 @@ class _FutureBuilderState<T> extends State<FutureBuilder<T>> {
@override
void initState() {
super.initState();
_snapshot = AsyncSnapshot<T>.withData(ConnectionState.none, widget.initialData);
// ignore: deprecated_member_use_from_same_package
_snapshot = widget.initialData == null
? AsyncSnapshot<T>.withoutData(ConnectionState.none)
// ignore: deprecated_member_use_from_same_package
: AsyncSnapshot<T>.withData(ConnectionState.none, widget.initialData);
_subscribe();
}
@ -614,7 +778,9 @@ class _FutureBuilderState<T> extends State<FutureBuilder<T>> {
widget.future.then<void>((T data) {
if (_activeCallbackIdentity == callbackIdentity) {
setState(() {
_snapshot = AsyncSnapshot<T>.withData(ConnectionState.done, data);
_snapshot = _TypeLiteral.isVoidType(T)
? AsyncSnapshot<T>.withoutData(ConnectionState.done)
: AsyncSnapshot<T>.withData(ConnectionState.done, data);
});
}
}, onError: (Object error) {
@ -632,3 +798,33 @@ class _FutureBuilderState<T> extends State<FutureBuilder<T>> {
_activeCallbackIdentity = null;
}
}
/// Class that allows callers to reference instances of [Type] that would
/// otherwise not be valid expressions.
///
/// Generic types and the `void` type are not usable as Dart expressions, so
/// the following statements are not legal and all yield compile-time errors:
///
/// ```dart
/// if (type == List<int>) print('msg');
/// if (type == void) print('msg');
/// Type type = List<int>;
/// ```
///
/// This class allows callers to get handles on such types, like so:
///
/// ```dart
/// if (type == const _TypeLiteral<List<int>>().type) print('msg');
/// if (type == const _TypeLiteral<void>().type) print('msg');
/// Type type = const _TypeLiteral<List<int>>().type;
/// ```
class _TypeLiteral<T> {
/// Creates a new [_TypeLiteral].
const _TypeLiteral();
/// Returns whether the specified type represents a "void" type.
static bool isVoidType(Type type) => type == const _TypeLiteral<void>().type;
/// The [Type] (`T`) represented by this [_TypeLiteral].
Type get type => T;
}

257
packages/flutter/test/widgets/async_test.dart
View File

@ -12,23 +12,33 @@ void main() {
return Text(snapshot.toString(), textDirection: TextDirection.ltr);
}
group('AsyncSnapshot', () {
test('requiring data succeeds if data is present', () {
expect(
const AsyncSnapshot<String>.withData(ConnectionState.done, 'hello').requireData,
'hello',
);
test('data succeeds if data is present', () {
const AsyncSnapshot<String> snapshot = AsyncSnapshot<String>.withData(ConnectionState.done, 'hello');
expect(snapshot.hasData, isTrue);
expect(snapshot.data, 'hello');
expect(snapshot.hasError, isFalse);
expect(snapshot.error, isNull);
});
test('requiring data fails if there is an error', () {
expect(
() => const AsyncSnapshot<String>.withError(ConnectionState.done, 'error').requireData,
throwsA(equals('error')),
);
test('data throws if there is an error', () {
const AsyncSnapshot<String> snapshot = AsyncSnapshot<String>.withError(ConnectionState.done, 'error');
expect(snapshot.hasData, isFalse);
expect(() => snapshot.data, throwsA(equals('error')));
expect(snapshot.hasError, isTrue);
expect(snapshot.error, 'error');
});
test('requiring data fails if snapshot has neither data nor error', () {
expect(
() => const AsyncSnapshot<String>.nothing().requireData,
throwsStateError,
);
test('data throws if created without data', () {
const AsyncSnapshot<String> snapshot = AsyncSnapshot<String>.withoutData(ConnectionState.none);
expect(snapshot.hasData, isFalse);
expect(() => snapshot.data, throwsStateError);
expect(snapshot.hasError, isFalse);
expect(snapshot.error, isNull);
});
test('data can be null', () {
const AsyncSnapshot<int> snapshot = AsyncSnapshot<int>.withData(ConnectionState.none, null);
expect(snapshot.hasData, isTrue);
expect(snapshot.data, isNull);
expect(snapshot.hasError, isFalse);
expect(snapshot.error, isNull);
});
});
group('Async smoke tests', () {
@ -40,7 +50,7 @@ void main() {
await eventFiring(tester);
});
testWidgets('StreamBuilder', (WidgetTester tester) async {
await tester.pumpWidget(StreamBuilder<String>(
await tester.pumpWidget(StreamBuilder<String>.withoutInitialData(
stream: Stream<String>.fromIterable(<String>['hello', 'world']),
builder: snapshotText,
));
@ -59,12 +69,12 @@ void main() {
await tester.pumpWidget(FutureBuilder<String>(
key: key, future: null, builder: snapshotText,
));
expect(find.text('AsyncSnapshot<String>(ConnectionState.none, null, null)'), findsOneWidget);
expect(find.text('AsyncSnapshot<String>(ConnectionState.none)'), findsOneWidget);
final Completer<String> completer = Completer<String>();
await tester.pumpWidget(FutureBuilder<String>(
key: key, future: completer.future, builder: snapshotText,
));
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting, null, null)'), findsOneWidget);
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting)'), findsOneWidget);
});
testWidgets('gracefully handles transition to null future', (WidgetTester tester) async {
final GlobalKey key = GlobalKey();
@ -72,14 +82,14 @@ void main() {
await tester.pumpWidget(FutureBuilder<String>(
key: key, future: completer.future, builder: snapshotText,
));
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting, null, null)'), findsOneWidget);
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting)'), findsOneWidget);
await tester.pumpWidget(FutureBuilder<String>(
key: key, future: null, builder: snapshotText,
));
expect(find.text('AsyncSnapshot<String>(ConnectionState.none, null, null)'), findsOneWidget);
expect(find.text('AsyncSnapshot<String>(ConnectionState.none)'), findsOneWidget);
completer.complete('hello');
await eventFiring(tester);
expect(find.text('AsyncSnapshot<String>(ConnectionState.none, null, null)'), findsOneWidget);
expect(find.text('AsyncSnapshot<String>(ConnectionState.none)'), findsOneWidget);
});
testWidgets('gracefully handles transition to other future', (WidgetTester tester) async {
final GlobalKey key = GlobalKey();
@ -88,125 +98,132 @@ void main() {
await tester.pumpWidget(FutureBuilder<String>(
key: key, future: completerA.future, builder: snapshotText,
));
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting, null, null)'), findsOneWidget);
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting)'), findsOneWidget);
await tester.pumpWidget(FutureBuilder<String>(
key: key, future: completerB.future, builder: snapshotText,
));
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting, null, null)'), findsOneWidget);
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting)'), findsOneWidget);
completerB.complete('B');
completerA.complete('A');
await eventFiring(tester);
expect(find.text('AsyncSnapshot<String>(ConnectionState.done, B, null)'), findsOneWidget);
expect(find.text('AsyncSnapshot<String>(ConnectionState.done, data: B)'), findsOneWidget);
});
testWidgets('tracks life-cycle of Future to success', (WidgetTester tester) async {
final Completer<String> completer = Completer<String>();
await tester.pumpWidget(FutureBuilder<String>(
future: completer.future, builder: snapshotText,
));
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting, null, null)'), findsOneWidget);
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting)'), findsOneWidget);
completer.complete('hello');
await eventFiring(tester);
expect(find.text('AsyncSnapshot<String>(ConnectionState.done, hello, null)'), findsOneWidget);
expect(find.text('AsyncSnapshot<String>(ConnectionState.done, data: hello)'), findsOneWidget);
});
testWidgets('tracks life-cycle of Future to error', (WidgetTester tester) async {
final Completer<String> completer = Completer<String>();
await tester.pumpWidget(FutureBuilder<String>(
future: completer.future, builder: snapshotText,
));
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting, null, null)'), findsOneWidget);
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting)'), findsOneWidget);
completer.completeError('bad');
await eventFiring(tester);
expect(find.text('AsyncSnapshot<String>(ConnectionState.done, null, bad)'), findsOneWidget);
expect(find.text('AsyncSnapshot<String>(ConnectionState.done, error: bad)'), findsOneWidget);
});
testWidgets('runs the builder using given initial data', (WidgetTester tester) async {
final GlobalKey key = GlobalKey();
await tester.pumpWidget(FutureBuilder<String>(
key: key,
future: null,
builder: snapshotText,
initialData: 'I',
));
expect(find.text('AsyncSnapshot<String>(ConnectionState.none, I, null)'), findsOneWidget);
});
testWidgets('ignores initialData when reconfiguring', (WidgetTester tester) async {
final GlobalKey key = GlobalKey();
await tester.pumpWidget(FutureBuilder<String>(
key: key,
future: null,
builder: snapshotText,
initialData: 'I',
));
expect(find.text('AsyncSnapshot<String>(ConnectionState.none, I, null)'), findsOneWidget);
testWidgets('produces snapshot with null data for null-completing data Future', (WidgetTester tester) async {
final Completer<String> completer = Completer<String>();
await tester.pumpWidget(FutureBuilder<String>(
key: key,
future: completer.future,
builder: snapshotText,
initialData: 'Ignored',
future: completer.future, builder: snapshotText,
));
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting, I, null)'), findsOneWidget);
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting)'), findsOneWidget);
completer.complete(null);
await eventFiring(tester);
expect(find.text('AsyncSnapshot<String>(ConnectionState.done, data: null)'), findsOneWidget);
});
testWidgets('produces snapshot with null data for Future<Null>', (WidgetTester tester) async {
final Completer<Null> completer = Completer<Null>(); // ignore: prefer_void_to_null
await tester.pumpWidget(FutureBuilder<Null>( // ignore: prefer_void_to_null
future: completer.future, builder: snapshotText,
));
expect(find.text('AsyncSnapshot<Null>(ConnectionState.waiting)'), findsOneWidget);
completer.complete();
await eventFiring(tester);
expect(find.text('AsyncSnapshot<Null>(ConnectionState.done, data: null)'), findsOneWidget);
});
testWidgets('produces snapshot with no data for Future<void>', (WidgetTester tester) async {
final Completer<void> completer = Completer<void>();
await tester.pumpWidget(
FutureBuilder<void>(
future: completer.future,
builder: (BuildContext context, AsyncSnapshot<void> snapshot) {
return Text(snapshot.toString(), textDirection: TextDirection.ltr);
},
),
);
expect(find.text('AsyncSnapshot<void>(ConnectionState.waiting)'), findsOneWidget);
completer.complete();
await eventFiring(tester);
expect(find.text('AsyncSnapshot<void>(ConnectionState.done)'), findsOneWidget);
});
});
group('StreamBuilder', () {
testWidgets('gracefully handles transition from null stream', (WidgetTester tester) async {
final GlobalKey key = GlobalKey();
await tester.pumpWidget(StreamBuilder<String>(
await tester.pumpWidget(StreamBuilder<String>.withoutInitialData(
key: key, stream: null, builder: snapshotText,
));
expect(find.text('AsyncSnapshot<String>(ConnectionState.none, null, null)'), findsOneWidget);
expect(find.text('AsyncSnapshot<String>(ConnectionState.none)'), findsOneWidget);
final StreamController<String> controller = StreamController<String>();
await tester.pumpWidget(StreamBuilder<String>(
await tester.pumpWidget(StreamBuilder<String>.withoutInitialData(
key: key, stream: controller.stream, builder: snapshotText,
));
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting, null, null)'), findsOneWidget);
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting)'), findsOneWidget);
});
testWidgets('gracefully handles transition to null stream', (WidgetTester tester) async {
final GlobalKey key = GlobalKey();
final StreamController<String> controller = StreamController<String>();
await tester.pumpWidget(StreamBuilder<String>(
await tester.pumpWidget(StreamBuilder<String>.withoutInitialData(
key: key, stream: controller.stream, builder: snapshotText,
));
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting, null, null)'), findsOneWidget);
await tester.pumpWidget(StreamBuilder<String>(
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting)'), findsOneWidget);
await tester.pumpWidget(StreamBuilder<String>.withoutInitialData(
key: key, stream: null, builder: snapshotText,
));
expect(find.text('AsyncSnapshot<String>(ConnectionState.none, null, null)'), findsOneWidget);
expect(find.text('AsyncSnapshot<String>(ConnectionState.none)'), findsOneWidget);
});
testWidgets('gracefully handles transition to other stream', (WidgetTester tester) async {
final GlobalKey key = GlobalKey();
final StreamController<String> controllerA = StreamController<String>();
final StreamController<String> controllerB = StreamController<String>();
await tester.pumpWidget(StreamBuilder<String>(
await tester.pumpWidget(StreamBuilder<String>.withoutInitialData(
key: key, stream: controllerA.stream, builder: snapshotText,
));
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting, null, null)'), findsOneWidget);
await tester.pumpWidget(StreamBuilder<String>(
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting)'), findsOneWidget);
await tester.pumpWidget(StreamBuilder<String>.withoutInitialData(
key: key, stream: controllerB.stream, builder: snapshotText,
));
controllerB.add('B');
controllerA.add('A');
await eventFiring(tester);
expect(find.text('AsyncSnapshot<String>(ConnectionState.active, B, null)'), findsOneWidget);
expect(find.text('AsyncSnapshot<String>(ConnectionState.active, data: B)'), findsOneWidget);
});
testWidgets('tracks events and errors of stream until completion', (WidgetTester tester) async {
final GlobalKey key = GlobalKey();
final StreamController<String> controller = StreamController<String>();
await tester.pumpWidget(StreamBuilder<String>(
await tester.pumpWidget(StreamBuilder<String>.withoutInitialData(
key: key, stream: controller.stream, builder: snapshotText,
));
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting, null, null)'), findsOneWidget);
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting)'), findsOneWidget);
controller.add('1');
controller.add('2');
await eventFiring(tester);
expect(find.text('AsyncSnapshot<String>(ConnectionState.active, 2, null)'), findsOneWidget);
expect(find.text('AsyncSnapshot<String>(ConnectionState.active, data: 2)'), findsOneWidget);
controller.add('3');
controller.addError('bad');
await eventFiring(tester);
expect(find.text('AsyncSnapshot<String>(ConnectionState.active, null, bad)'), findsOneWidget);
expect(find.text('AsyncSnapshot<String>(ConnectionState.active, error: bad)'), findsOneWidget);
controller.add('4');
controller.close();
await eventFiring(tester);
expect(find.text('AsyncSnapshot<String>(ConnectionState.done, 4, null)'), findsOneWidget);
expect(find.text('AsyncSnapshot<String>(ConnectionState.done, data: 4)'), findsOneWidget);
});
testWidgets('runs the builder using given initial data', (WidgetTester tester) async {
final StreamController<String> controller = StreamController<String>();
@ -215,7 +232,7 @@ void main() {
builder: snapshotText,
initialData: 'I',
));
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting, I, null)'), findsOneWidget);
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting, data: I)'), findsOneWidget);
});
testWidgets('ignores initialData when reconfiguring', (WidgetTester tester) async {
final GlobalKey key = GlobalKey();
@ -225,7 +242,7 @@ void main() {
builder: snapshotText,
initialData: 'I',
));
expect(find.text('AsyncSnapshot<String>(ConnectionState.none, I, null)'), findsOneWidget);
expect(find.text('AsyncSnapshot<String>(ConnectionState.none, data: I)'), findsOneWidget);
final StreamController<String> controller = StreamController<String>();
await tester.pumpWidget(StreamBuilder<String>(
key: key,
@ -233,7 +250,69 @@ void main() {
builder: snapshotText,
initialData: 'Ignored',
));
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting, I, null)'), findsOneWidget);
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting, data: I)'), findsOneWidget);
});
testWidgets('produces snapshots with null data for null-producing stream', (WidgetTester tester) async {
final GlobalKey key = GlobalKey();
final StreamController<String> controller = StreamController<String>();
await tester.pumpWidget(StreamBuilder<String>.withoutInitialData(
key: key,
stream: controller.stream,
builder: snapshotText,
));
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting)'), findsOneWidget);
controller.add(null);
await eventFiring(tester);
expect(find.text('AsyncSnapshot<String>(ConnectionState.active, data: null)'), findsOneWidget);
controller.addError('bad');
await eventFiring(tester);
expect(find.text('AsyncSnapshot<String>(ConnectionState.active, error: bad)'), findsOneWidget);
controller.add(null);
controller.close();
await eventFiring(tester);
expect(find.text('AsyncSnapshot<String>(ConnectionState.done, data: null)'), findsOneWidget);
});
testWidgets('produces snapshots with null data for Stream<Null>', (WidgetTester tester) async {
final GlobalKey key = GlobalKey();
final StreamController<Null> controller = StreamController<Null>(); // ignore: prefer_void_to_null
await tester.pumpWidget(StreamBuilder<Null>.withoutInitialData( // ignore: prefer_void_to_null
key: key,
stream: controller.stream,
builder: snapshotText,
));
expect(find.text('AsyncSnapshot<Null>(ConnectionState.waiting)'), findsOneWidget);
controller.add(null);
await eventFiring(tester);
expect(find.text('AsyncSnapshot<Null>(ConnectionState.active, data: null)'), findsOneWidget);
controller.addError('bad');
await eventFiring(tester);
expect(find.text('AsyncSnapshot<Null>(ConnectionState.active, error: bad)'), findsOneWidget);
controller.add(null);
controller.close();
await eventFiring(tester);
expect(find.text('AsyncSnapshot<Null>(ConnectionState.done, data: null)'), findsOneWidget);
});
testWidgets('produces snapshots with no data for Stream<void>', (WidgetTester tester) async {
final GlobalKey key = GlobalKey();
final StreamController<void> controller = StreamController<void>();
await tester.pumpWidget(StreamBuilder<void>.withoutInitialData(
key: key,
stream: controller.stream,
builder: (BuildContext context, AsyncSnapshot<void> snapshot) {
return Text(snapshot.toString(), textDirection: TextDirection.ltr);
},
));
expect(find.text('AsyncSnapshot<void>(ConnectionState.waiting)'), findsOneWidget);
controller.add(null);
await eventFiring(tester);
expect(find.text('AsyncSnapshot<void>(ConnectionState.active)'), findsOneWidget);
controller.addError('bad');
await eventFiring(tester);
expect(find.text('AsyncSnapshot<void>(ConnectionState.active, error: bad)'), findsOneWidget);
controller.add(null);
controller.close();
await eventFiring(tester);
expect(find.text('AsyncSnapshot<void>(ConnectionState.done)'), findsOneWidget);
});
});
group('FutureBuilder and StreamBuilder behave identically on Stream from Future', () {
@ -241,48 +320,30 @@ void main() {
final Completer<String> completer = Completer<String>();
await tester.pumpWidget(Column(children: <Widget>[
FutureBuilder<String>(future: completer.future, builder: snapshotText),
StreamBuilder<String>(stream: completer.future.asStream(), builder: snapshotText),
StreamBuilder<String>.withoutInitialData(stream: completer.future.asStream(), builder: snapshotText),
]));
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting, null, null)'), findsNWidgets(2));
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting)'), findsNWidgets(2));
completer.complete('hello');
await eventFiring(tester);
expect(find.text('AsyncSnapshot<String>(ConnectionState.done, hello, null)'), findsNWidgets(2));
expect(find.text('AsyncSnapshot<String>(ConnectionState.done, data: hello)'), findsNWidgets(2));
});
testWidgets('when completing with error', (WidgetTester tester) async {
final Completer<String> completer = Completer<String>();
await tester.pumpWidget(Column(children: <Widget>[
FutureBuilder<String>(future: completer.future, builder: snapshotText),
StreamBuilder<String>(stream: completer.future.asStream(), builder: snapshotText),
StreamBuilder<String>.withoutInitialData(stream: completer.future.asStream(), builder: snapshotText),
]));
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting, null, null)'), findsNWidgets(2));
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting)'), findsNWidgets(2));
completer.completeError('bad');
await eventFiring(tester);
expect(find.text('AsyncSnapshot<String>(ConnectionState.done, null, bad)'), findsNWidgets(2));
expect(find.text('AsyncSnapshot<String>(ConnectionState.done, error: bad)'), findsNWidgets(2));
});
testWidgets('when Future is null', (WidgetTester tester) async {
await tester.pumpWidget(Column(children: <Widget>[
FutureBuilder<String>(future: null, builder: snapshotText),
StreamBuilder<String>(stream: null, builder: snapshotText),
StreamBuilder<String>.withoutInitialData(stream: null, builder: snapshotText),
]));
expect(find.text('AsyncSnapshot<String>(ConnectionState.none, null, null)'), findsNWidgets(2));
});
testWidgets('when initialData is used with null Future and Stream', (WidgetTester tester) async {
await tester.pumpWidget(Column(children: <Widget>[
FutureBuilder<String>(future: null, builder: snapshotText, initialData: 'I'),
StreamBuilder<String>(stream: null, builder: snapshotText, initialData: 'I'),
]));
expect(find.text('AsyncSnapshot<String>(ConnectionState.none, I, null)'), findsNWidgets(2));
});
testWidgets('when using initialData and completing with data', (WidgetTester tester) async {
final Completer<String> completer = Completer<String>();
await tester.pumpWidget(Column(children: <Widget>[
FutureBuilder<String>(future: completer.future, builder: snapshotText, initialData: 'I'),
StreamBuilder<String>(stream: completer.future.asStream(), builder: snapshotText, initialData: 'I'),
]));
expect(find.text('AsyncSnapshot<String>(ConnectionState.waiting, I, null)'), findsNWidgets(2));
completer.complete('hello');
await eventFiring(tester);
expect(find.text('AsyncSnapshot<String>(ConnectionState.done, hello, null)'), findsNWidgets(2));
expect(find.text('AsyncSnapshot<String>(ConnectionState.none)'), findsNWidgets(2));
});
});
group('StreamBuilderBase', () {