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container.dart
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container.dart
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part of '../framework.dart';
ProviderBase? _circularDependencyLock;
int _debugNextId = 0;
class _FamilyOverrideRef {
_FamilyOverrideRef(this.override, this.container);
FamilyOverride override;
final ProviderContainer container;
}
/// An object that contains a [ProviderElementBase].
///
/// This object is used to implement the scoping mechanism of providers,
/// by allowing a [ProviderContainer] to "inherit" the [_StateReader]s from
/// its ancestor, while preserving the "mount providers on demand" logic.
class _StateReader {
_StateReader({
required this.origin,
required this.override,
required this.container,
required this.isDynamicallyCreated,
});
final ProviderBase origin;
ProviderBase override;
final ProviderContainer container;
/// Whether the [_StateReader] was created on first provider read instead of
/// at the creation of the [ProviderContainer]
final bool isDynamicallyCreated;
ProviderElementBase? _element;
ProviderElementBase getElement() => _element ??= _create();
ProviderElementBase _create() {
if (origin == _circularDependencyLock) {
throw CircularDependencyError._();
}
_circularDependencyLock ??= origin;
try {
final element = override.createElement()
.._provider = override
.._origin = origin
.._container = container
..mount();
element.getState()!.map<void>(
// ignore: avoid_types_on_closure_parameters
data: (ResultData<Object?> data) {
for (final observer in container._observers) {
runTernaryGuarded(
observer.didAddProvider,
origin,
data.state,
container,
);
}
},
error: (error) {
for (final observer in container._observers) {
runTernaryGuarded(
observer.didAddProvider,
origin,
null,
container,
);
}
for (final observer in container._observers) {
runQuaternaryGuarded(
observer.providerDidFail,
origin,
error.error,
error.stackTrace,
container,
);
}
},
);
return element;
} finally {
if (_circularDependencyLock == origin) {
_circularDependencyLock = null;
}
}
}
}
var _debugVerifyDependenciesAreRespectedEnabled = true;
/// {@template riverpod.providercontainer}
/// An object that stores the state of the providers and allows overriding the
/// behavior of a specific provider.
///
/// If you are using Flutter, you do not need to care about this object
/// (outside of testing), as it is implicitly created for you by `ProviderScope`.
/// {@endtemplate}
@sealed
class ProviderContainer implements Node {
/// {@macro riverpod.providercontainer}
ProviderContainer({
ProviderContainer? parent,
List<Override> overrides = const [],
List<ProviderObserver>? observers,
}) : _debugOverridesLength = overrides.length,
depth = parent == null ? 0 : parent.depth + 1,
_parent = parent,
_observers = [
...?observers,
if (parent != null) ...parent._observers,
],
_stateReaders = {
if (parent != null)
for (final entry in parent._stateReaders.entries)
if (!entry.value.isDynamicallyCreated) entry.key: entry.value,
},
_root = parent?._root ?? parent {
assert(
() {
_debugId = '${_debugNextId++}';
RiverpodBinding.debugInstance.containers = {
...RiverpodBinding.debugInstance.containers,
_debugId: this,
};
return true;
}(),
'',
);
if (parent != null) {
parent._children.add(this);
_overrideForFamily.addAll(parent._overrideForFamily);
}
for (final override in overrides) {
if (override is ProviderOverride) {
_overrideForProvider[override._origin] = override._override;
_stateReaders[override._origin] = _StateReader(
origin: override._origin,
override: override._override,
container: this,
isDynamicallyCreated: false,
);
} else if (override is FamilyOverride) {
_overrideForFamily[override.overriddenFamily] = _FamilyOverrideRef(
override,
this,
);
}
}
}
final int _debugOverridesLength;
/// A function that controls the refresh rate of providers.
///
/// Defaults to refreshing providers at the end of the next event-loop.
@Deprecated('Will be removed in 3.0.0')
@internal
void Function(void Function() task) get vsync {
return vsyncOverride ?? _defaultVsync;
}
/// A way to override [vsync], used by Flutter to synchronize a container
/// with the widget tree.
@Deprecated('Will be removed in 3.0.0')
@internal
void Function(void Function() task)? vsyncOverride;
/// The object that handles when providers are refreshed and disposed.
late final _ProviderScheduler _scheduler =
_parent?._scheduler ?? _ProviderScheduler();
late final String _debugId;
/// How deep this [ProviderContainer] is in the graph of containers.
///
/// Starts at 0.
final int depth;
/// A unique ID for this object, used by the devtool to differentiate two [ProviderContainer].
///
/// Should not be used.
@visibleForTesting
String get debugId {
String? id;
assert(
() {
id = _debugId;
return true;
}(),
'',
);
return id!;
}
final ProviderContainer? _root;
final ProviderContainer? _parent;
final _children = <ProviderContainer>[];
/// All the containers that have this container as `parent`.
///
/// Do not use in production
List<ProviderContainer> get debugChildren => UnmodifiableListView(_children);
final _overrideForProvider = HashMap<ProviderBase, ProviderBase>();
final _overrideForFamily = HashMap<Family, _FamilyOverrideRef>();
final Map<ProviderBase, _StateReader> _stateReaders;
/// Awaits for providers to rebuild/be disposed and for listeners to be notified.
Future<void> pump() async {
return _scheduler.pendingFuture;
}
final List<ProviderObserver> _observers;
/// A debug utility used by `flutter_riverpod`/`hooks_riverpod` to check
/// if it is safe to modify a provider.
///
/// This corresponds to all the widgets that a [Provider] is associated with.
@Deprecated('Will be removed in 3.0.0')
@internal
void Function()? debugCanModifyProviders;
/// Whether [dispose] was called or not.
///
/// This disables the different methods of [ProviderContainer], resulting in
/// a [StateError] when attempting to use them.
bool _disposed = false;
/// Reads a provider without listening to it and returns the currently
/// exposed value.
///
/// ```dart
/// final greetingProvider = Provider((_) => 'Hello world');
///
/// void main() {
/// final container = ProviderContainer();
///
/// print(container.read(greetingProvider)); // Hello World
/// }
/// ```
Result read<Result>(
ProviderListenable<Result> provider,
) {
return provider.read(this);
}
/// {@macro riverpod.exists}
bool exists(ProviderBase<Object?> provider) {
final element = _stateReaders[provider]?._element;
return element != null;
}
/// Executes [ProviderElementBase.debugReassemble] on all the providers.
void debugReassemble() {
// TODO hot-reload handle provider type change
// TODO hot-reload handle provider response type change
// TODO hot-reload handle provider -> family
// TODO hot-reload handle family adding parameters
// TODO found "Future already completed error" after adding family parameter
assert(
() {
for (final element in getAllProviderElements()) {
element.debugReassemble();
}
return true;
}(),
'',
);
}
@override
ProviderSubscription<State> _listenElement<State>(
ProviderElementBase<State> element, {
required void Function(State? previous, State next) listener,
required void Function(Object error, StackTrace stackTrace) onError,
}) {
final sub = _ExternalProviderSubscription<State>._(
element,
listener,
onError: onError,
);
element._externalDependents.add(sub);
return sub;
}
/// {@macro riverpod.listen}
@override
ProviderSubscription<State> listen<State>(
ProviderListenable<State> provider,
void Function(State? previous, State next) listener, {
bool fireImmediately = false,
void Function(Object error, StackTrace stackTrace)? onError,
}) {
// TODO test always flushed provider
return provider.addListener(
this,
listener,
fireImmediately: fireImmediately,
onError: onError,
onDependencyMayHaveChanged: null,
);
}
/// {@template riverpod.invalidate}
void invalidate(ProviderOrFamily provider) {
if (provider is ProviderBase) {
final reader = _getStateReader(provider._origin);
reader._element?.invalidateSelf();
} else {
provider as Family;
final familyContainer =
_overrideForFamily[provider]?.container ?? _root ?? this;
for (final stateReader in familyContainer._stateReaders.values) {
if (stateReader.origin.from != provider) continue;
stateReader._element?.invalidateSelf();
}
}
}
/// {@template riverpod.refresh}
State refresh<State>(Refreshable<State> provider) {
invalidate(provider._origin);
return read(provider);
}
void _disposeProvider(ProviderBase<Object?> provider) {
final element = readProviderElement(provider);
element.dispose();
final reader = _stateReaders[element._origin]!;
if (reader.isDynamicallyCreated) {
// Since the StateReader is implicitly created, we don't keep it
// on provider dispose, to avoid memory leak
void removeStateReaderFrom(ProviderContainer container) {
if (container._stateReaders[element._origin] == reader) {
container._stateReaders.remove(element._origin);
container._children.forEach(removeStateReaderFrom);
}
}
removeStateReaderFrom(this);
} else {
reader._element = null;
}
}
/// Updates the list of provider overrides.
///
/// If you are using flutter, this is done implicitly for you by `ProviderScope`.
///
/// Updating a `overrideWithValue` with a different value
/// will cause the listeners to rebuild.
///
/// It is not possible, to remove or add new overrides, only update existing ones.
void updateOverrides(List<Override> overrides) {
if (_disposed) {
throw StateError(
'Called updateOverrides on a ProviderContainer that was already disposed',
);
}
assert(
_debugOverridesLength == overrides.length,
'Tried to change the number of overrides. This is not allowed – '
'overrides cannot be removed/added, they can only be updated.',
);
List<Override>? unusedOverrides;
assert(
() {
unusedOverrides = [...overrides];
return true;
}(),
'',
);
for (final override in overrides) {
if (override is ProviderOverride) {
assert(
() {
unusedOverrides!.remove(override);
return true;
}(),
'',
);
assert(
_overrideForProvider[override._origin].runtimeType ==
override._override.runtimeType,
'Replaced the override of type ${_overrideForProvider[override._origin].runtimeType} '
'with an override of type ${override._override.runtimeType}, which is different.\n'
'Changing the kind of override or reordering overrides is not supported.',
);
// _stateReaders[origin] cannot be null for overridden providers.
final reader = _stateReaders[override._origin]!;
reader.override =
_overrideForProvider[override._origin] = override._override;
final element = reader._element;
if (element == null) continue;
runUnaryGuarded(element.update, override._override);
} else if (override is FamilyOverride) {
assert(
() {
unusedOverrides!.remove(override);
return true;
}(),
'',
);
// TODO assert family override did not change
_overrideForFamily[override.overriddenFamily]!.override = override;
}
}
assert(
unusedOverrides!.isEmpty,
'Updated the list of overrides with providers that were not overridden before',
);
}
@override
ProviderElementBase<State> readProviderElement<State>(
ProviderBase<State> provider,
) {
if (_disposed) {
throw StateError(
'Tried to read a provider from a ProviderContainer that was already disposed',
);
}
final reader = _getStateReader(provider);
assert(
() {
// Avoid having the assert trigger itself exponentially
if (!_debugVerifyDependenciesAreRespectedEnabled) return true;
try {
_debugVerifyDependenciesAreRespectedEnabled = false;
// Check that this containers doesn't have access to an overridden
// dependency of the targeted provider
final targetElement = reader.getElement();
final visitedDependencies = <ProviderBase>{};
final queue = Queue<ProviderBase>();
targetElement.visitAncestors((e) => queue.add(e.origin));
while (queue.isNotEmpty) {
final dependency = queue.removeFirst();
if (visitedDependencies.add(dependency)) {
final dependencyElement =
readProviderElement<Object?>(dependency);
assert(
targetElement.provider != targetElement.origin ||
dependencyElement ==
targetElement.container
.readProviderElement<Object?>(dependency),
'''
Tried to read $provider from a place where one of its dependencies were overridden but the provider is not.
To fix this error, you can add add "dependencies" to $provider such that we have:
```
final a = Provider(...);
final b = Provider((ref) => ref.watch(a), dependencies: [a]);
```
''',
);
dependencyElement.visitAncestors((e) => queue.add(e.origin));
}
}
} finally {
_debugVerifyDependenciesAreRespectedEnabled = true;
}
return true;
}(),
'',
);
return reader.getElement() as ProviderElementBase<State>;
}
_StateReader _getStateReader(ProviderBase provider) {
final currentReader = _stateReaders[provider];
if (currentReader != null) return currentReader;
_StateReader getReader() {
if (provider.from != null) {
// reading a family
final familyOverrideRef = _overrideForFamily[provider.from];
if (familyOverrideRef != null) {
// A family was overridden, so we implicitly mount the readers
if (familyOverrideRef.container._stateReaders.containsKey(provider)) {
return familyOverrideRef.container._stateReaders[provider]!;
}
void setupOverride({
required ProviderBase origin,
required ProviderBase override,
}) {
assert(
origin == override || override.dependencies == null,
'A provider override cannot specify `dependencies`',
);
// setupOverride may be called multiple times on different providers
// of the same family (provider vs provider.modifier), so we use ??=
// to initialize the providers only once
familyOverrideRef.container._stateReaders[origin] ??= _StateReader(
origin: origin,
override: override,
container: familyOverrideRef.container,
isDynamicallyCreated: true,
);
}
final providerOverride =
familyOverrideRef.override.getProviderOverride(provider);
setupOverride(origin: provider, override: providerOverride);
// if setupOverride overrode the provider, it was already initialized
// in the code above. Otherwise we initialize it as if it was not overridden
return familyOverrideRef.container._stateReaders[provider] ??
_StateReader(
origin: provider,
override: provider,
container: familyOverrideRef.container,
isDynamicallyCreated: true,
);
}
}
final root = _root;
if (root != null) {
// On scoped containers, check for implicit override.
final dependencies = provider.from?.allTransitiveDependencies ??
provider.allTransitiveDependencies;
final containerForDependencyOverride = dependencies
?.map((dep) {
final reader = _stateReaders[dep];
if (reader != null) {
return reader.container;
}
final familyOverride = _overrideForFamily[dep];
return familyOverride?.container;
})
.where((container) => container != null)
.toList();
if (containerForDependencyOverride != null &&
containerForDependencyOverride.isNotEmpty) {
// a dependency of the provider was overridden, so the provider is overridden too
final deepestOverrideContainer = containerForDependencyOverride
.fold<ProviderContainer>(root, (previous, container) {
if (container!.depth > previous.depth) {
return container;
}
return previous;
});
/// Insert the StateReader in the container that it belongs to,
/// and import it locally
return deepestOverrideContainer._stateReaders.putIfAbsent(provider,
() {
return _StateReader(
origin: provider,
override: provider,
container: deepestOverrideContainer,
isDynamicallyCreated: true,
);
});
}
}
if (_root?._stateReaders.containsKey(provider) ?? false) {
// For un-overridden providers, it is possible that the provider was
// read in the root ProviderContainer before this container. In which case
// we reuse the existing state instead of creating a new one.
return _root!._stateReaders[provider]!;
}
// The provider had no existing state and no override, so we're
// mounting it on the root container.
final reader = _StateReader(
origin: provider,
// If a provider did not have an associated StateReader then it is
// guaranteed to not be overridden
override: provider,
container: _root ?? this,
isDynamicallyCreated: true,
);
if (_root != null) {
_root!._stateReaders[provider] = reader;
}
return reader;
}
return _stateReaders[provider] = getReader();
}
/// Release all the resources associated with this [ProviderContainer].
///
/// This will destroy the state of all providers associated with this
/// [ProviderContainer] and call [Ref.onDispose] listeners.
void dispose() {
if (_disposed) {
return;
}
assert(
() {
RiverpodBinding.debugInstance.containers =
Map.from(RiverpodBinding.debugInstance.containers)
..remove(_debugId);
return true;
}(),
'',
);
_parent?._children.remove(this);
_disposed = true;
for (final element in getAllProviderElementsInOrder().toList().reversed) {
element.dispose();
}
if (_root == null) _scheduler.dispose();
}
/// Traverse the [ProviderElementBase]s associated with this [ProviderContainer].
Iterable<ProviderElementBase> getAllProviderElements() sync* {
for (final reader in _stateReaders.values) {
if (reader._element != null && reader.container == this) {
yield reader._element!;
}
}
}
/// Visit all nodes of the graph at most once, from roots to leaves.
///
/// This is fairly expensive and should be avoided as much as possible.
/// If you do not need for providers to be sorted, consider using [getAllProviderElements]
/// instead, which returns an unsorted list and is significantly faster.
Iterable<ProviderElementBase> getAllProviderElementsInOrder() sync* {
final visitedNodes = HashSet<ProviderElementBase>();
final queue = DoubleLinkedQueue<ProviderElementBase>();
// get providers that don't depend on other providers from this container
for (final reader in _stateReaders.values) {
if (reader.container != this) continue;
final element = reader._element;
if (element == null) continue;
var hasAncestorsInContainer = false;
element.visitAncestors((element) {
// We ignore dependencies that are defined in another container, as
// they are in a separate graph
if (element._container == this) {
hasAncestorsInContainer = true;
}
});
if (!hasAncestorsInContainer) {
queue.add(element);
}
}
while (queue.isNotEmpty) {
final element = queue.removeFirst();
if (!visitedNodes.add(element)) {
// Already visited
continue;
}
yield element;
// Queue the children of this element, but only if all of its ancestors
// were already visited before.
// If a child does not have all of its ancestors visited, when those
// ancestors will be visited, they will retry visiting this child.
element.visitChildren(
elementVisitor: (dependent) {
if (dependent.container == this) {
// All the parents of a node must have been visited before a node is visited
var areAllAncestorsAlreadyVisited = true;
dependent.visitAncestors((e) {
if (e._container == this && !visitedNodes.contains(e)) {
areAllAncestorsAlreadyVisited = false;
}
});
if (areAllAncestorsAlreadyVisited) queue.add(dependent);
}
},
// We only care about Elements here, so let's ignore notifiers
notifierVisitor: (_) {},
);
}
}
}
/// An object that listens to the changes of a [ProviderContainer].
///
/// This can be used for logging or making devtools.
abstract class ProviderObserver {
/// An object that listens to the changes of a [ProviderContainer].
///
/// This can be used for logging or making devtools.
const ProviderObserver();
/// A provider was initialized, and the value exposed is [value].
///
/// [value] will be `null` if the provider threw during initialization.
void didAddProvider(
ProviderBase provider,
Object? value,
ProviderContainer container,
) {}
/// A provider emitted an error, be it by throwing during initialization
/// or by having a [Future]/[Stream] emit an error
void providerDidFail(
ProviderBase provider,
Object error,
StackTrace stackTrace,
ProviderContainer container,
) {}
/// Called my providers when they emit a notification.
///
/// - [newValue] will be `null` if the provider threw during initialization.
/// - [previousValue] will be `null` if the previous build threw during initialization.
void didUpdateProvider(
ProviderBase provider,
Object? previousValue,
Object? newValue,
ProviderContainer container,
) {}
/// A provider was disposed
void didDisposeProvider(
ProviderBase provider,
ProviderContainer container,
) {}
}
/// An implementation detail for the override mechanism of providers
@internal
typedef SetupOverride = void Function({
required ProviderBase origin,
required ProviderBase override,
});
/// An object used by [ProviderContainer] to override the behavior of a provider
/// for a part of the application.
///
/// Do not implement/extend this class.
///
/// See also:
///
/// - [ProviderContainer], which uses this object.
/// - `overrideWithValue`, which creates a [ProviderOverride].
@internal
class ProviderOverride implements Override {
/// Override a provider
ProviderOverride({
required ProviderBase origin,
required ProviderBase override,
}) : _origin = origin,
_override = override;
/// The provider that is overridden.
final ProviderBase _origin;
/// The new provider behaviour.
final ProviderBase _override;
}
/// An object used by [ProviderContainer]/`ProviderScope` to override the behavior
/// of a provider/family for part of the application.
///
/// Do not extend or implement.
abstract class Override {}
/// An error thrown when a call to [Ref.read]/[Ref.watch]
/// leads to a provider depending on itself.
///
/// Circular dependencies are both not supported for performance reasons
/// and maintainability reasons.
/// Consider reading about unidirectional data flow to learn about the
/// benefits of avoiding circular dependencies.
class CircularDependencyError extends Error {
CircularDependencyError._();
}