Allow users to bypass observability system for performance; Avoid unnecessary observable notifications of @observable fields of Stores; Fix Reaction lacks toString, so cannot see which reaction causes the error; Add StackTrace to reactions in debug mode to easily spot which reaction it is

mobx/lib/src/api/observable_collections/observable_list.dart

@@ -40,6 +40,8 @@ class ObservableList<T>
  final Atom _atom;
  final List<T> _list;
 
+ List<T> get nonObservableInner => _list;
+
  Listeners<ListChange<T>>? _listenersField;
 
  Listeners<ListChange<T>> get _listeners =>

mobx/lib/src/api/observable_collections/observable_map.dart

@@ -58,6 +58,8 @@ class ObservableMap<K, V>
  final Atom _atom;
  final Map<K, V> _map;
 
+ Map<K, V> get nonObservableInner => _map;
+
  String get name => _atom.name;
 
  Listeners<MapChange<K, V>>? _listenersField;

mobx/lib/src/api/observable_collections/observable_set.dart

@@ -46,6 +46,8 @@ class ObservableSet<T>
  final Atom _atom;
  final Set<T> _set;
 
+ Set<T> get nonObservableInner => _set;
+
  String get name => _atom.name;
 
  Listeners<SetChange<T>>? _listenersField;

mobx/lib/src/core/action.dart

@@ -1,6 +1,6 @@
 part of '../core.dart';
 
-class Action {
+class Action with DebugCreationStack {
  /// Creates an action that encapsulates all the mutations happening on the
  /// observables.
  ///
@@ -61,6 +61,10 @@ class Action {
  _controller.endAction(runInfo);
  }
  }
+
+ @override
+ String toString() =>
+ 'Action(name: $name, identity: ${identityHashCode(this)})';
 }
 
 /// `ActionController` is used to define the start/end boundaries of code which

mobx/lib/src/core/atom.dart

@@ -5,7 +5,7 @@ enum _ListenerKind {
  onBecomeUnobserved,
 }
 
-class Atom {
+class Atom with DebugCreationStack {
  /// Creates a simple Atom for tracking its usage in a reactive context. This is useful when
  /// you don't need the value but instead a way of knowing when it becomes active and inactive
  /// in a reaction.
@@ -42,6 +42,8 @@ class Atom {
 
  DerivationState _lowestObserverState = DerivationState.notTracking;
 
+ bool get isBeingObserved => _isBeingObserved;
+
  // ignore: prefer_final_fields
  bool _isBeingObserved = false;
 
@@ -114,6 +116,9 @@ class Atom {
  }
  };
  }
+
+ @override
+ String toString() => 'Atom(name: $name, identity: ${identityHashCode(this)})';
 }
 
 class WillChangeNotification<T> {

mobx/lib/src/core/atom_extensions.dart

@@ -7,6 +7,11 @@ extension AtomSpyReporter on Atom {
  }
 
  void reportWrite<T>(T newValue, T oldValue, void Function() setNewValue) {
+ // Avoid unnecessary observable notifications of @observable fields of Stores
+ if (newValue == oldValue) {
+ return;
+ }
+
  context.spyReport(ObservableValueSpyEvent(this,
  newValue: newValue, oldValue: oldValue, name: name));
 

mobx/lib/src/core/computed.dart

@@ -181,4 +181,8 @@ class Computed<T> extends Atom implements Derivation, ObservableValue<T> {
  }, context: _context)
  .call;
  }
+
+ @override
+ String toString() =>
+ 'Computed<$T>(name: $name, identity: ${identityHashCode(this)})';
 }

mobx/lib/src/core/context.dart

@@ -343,7 +343,9 @@ class ReactiveContext {
  _resetState();
 
  throw MobXCyclicReactionException(
- "Reaction doesn't converge to a stable state after ${config.maxIterations} iterations. Probably there is a cycle in the reactive function: $failingReaction");
+ "Reaction doesn't converge to a stable state after ${config.maxIterations} iterations. "
+ "Probably there is a cycle in the reactive function: $failingReaction "
+ "(creation stack: ${failingReaction.debugCreationStack})");
  }
 
  final remainingReactions = allReactions.toList(growable: false);

mobx/lib/src/core/observable.dart

@@ -53,6 +53,8 @@ class Observable<T> extends Atom
  return _value;
  }
 
+ T get nonObservableValue => _value;
+
  set value(T value) {
  _context.enforceWritePolicy(this);
 
@@ -125,4 +127,8 @@ class Observable<T> extends Atom
  @override
  Dispose intercept(Interceptor<T> interceptor) =>
  _interceptors.add(interceptor);
+
+ @override
+ String toString() =>
+ 'Observable<$T>(name: $name, identity: ${identityHashCode(this)})';
 }

mobx/lib/src/core/reaction.dart

@@ -6,9 +6,11 @@ abstract class Reaction implements Derivation {
  void dispose();
 
  void _run();
+
+ StackTrace? get debugCreationStack;
 }
 
-class ReactionImpl implements Reaction {
+class ReactionImpl with DebugCreationStack implements Reaction {
  ReactionImpl(this._context, Function() onInvalidate,
  {required this.name, void Function(Object, Reaction)? onError}) {
  _onInvalidate = onInvalidate;
@@ -180,4 +182,8 @@ class ReactionImpl implements Reaction {
 
  _context._notifyReactionErrorHandlers(exception, this);
  }
+
+ @override
+ String toString() =>
+ 'Reaction(name: $name, identity: ${identityHashCode(this)})';
 }

mobx/lib/src/utils.dart

@@ -4,3 +4,19 @@ const Duration ms = Duration(milliseconds: 1);
 
 Timer Function(void Function()) createDelayedScheduler(int delayMs) =>
  (fn) => Timer(ms * delayMs, fn);
+
+mixin DebugCreationStack {
+ /// Set the flag to true, to enable [debugCreationStack].
+ /// Otherwise, the stack is always null.
+ static var enable = false;
+
+ /// The stack trace when the object is created
+ final StackTrace? debugCreationStack = () {
+ StackTrace? result;
+ assert(() {
+ if (enable) result = StackTrace.current;
+ return true;
+ }());
+ return result;
+ }();
+}

mobx/test/action_test.dart

@@ -1,4 +1,5 @@
 import 'package:mobx/mobx.dart';
+import 'package:mobx/src/utils.dart';
 import 'package:mocktail/mocktail.dart' as mock;
 import 'package:test/test.dart';
 
@@ -11,6 +12,18 @@ void main() {
  testSetup();
 
  group('Action', () {
+ test('toString', () {
+ final object = Action(() {}, name: 'MyName');
+ expect(object.toString(), contains('MyName'));
+ });
+
+ test('debugCreationStack', () {
+ DebugCreationStack.enable = true;
+ addTearDown(() => DebugCreationStack.enable = false);
+ final object = Action(() {});
+ expect(object.debugCreationStack, isNotNull);
+ });
+
  test('basics work', () {
  final a = Action((String name, String value) {
  expect(name, equals('name'));

mobx/test/atom_extensions_test.dart

@@ -0,0 +1,61 @@
+import 'package:mobx/mobx.dart';
+import 'package:test/test.dart';
+
+void main() {
+ test(
+ 'when write to @observable field with changed value, should trigger notifications for downstream',
+ () {
+ final store = _ExampleStore();
+
+ final autorunResults = <String>[];
+ autorun((_) => autorunResults.add(store.value));
+
+ expect(autorunResults, ['first']);
+
+ store.value = 'second';
+
+ expect(autorunResults, ['first', 'second']);
+ });
+
+ // fixed by #855
+ test(
+ 'when write to @observable field with unchanged value, should not trigger notifications for downstream',
+ () {
+ final store = _ExampleStore();
+
+ final autorunResults = <String>[];
+ autorun((_) => autorunResults.add(store.value));
+
+ expect(autorunResults, ['first']);
+
+ store.value = store.value;
+
+ expect(autorunResults, ['first']);
+ });
+}
+
+class _ExampleStore = __ExampleStore with _$_ExampleStore;
+
+abstract class __ExampleStore with Store {
+ @observable
+ String value = 'first';
+}
+
+// This is what typically a mobx codegen will generate.
+mixin _$_ExampleStore on __ExampleStore, Store {
+ // ignore: non_constant_identifier_names
+ late final _$valueAtom = Atom(name: '__ExampleStore.value', context: context);
+
+ @override
+ String get value {
+ _$valueAtom.reportRead();
+ return super.value;
+ }
+
+ @override
+ set value(String value) {
+ _$valueAtom.reportWrite(value, super.value, () {
+ super.value = value;
+ });
+ }
+}

mobx/test/computed_test.dart

@@ -1,5 +1,6 @@
 import 'package:collection/collection.dart';
 import 'package:mobx/mobx.dart' hide when;
+import 'package:mobx/src/utils.dart';
 import 'package:mocktail/mocktail.dart';
 import 'package:test/test.dart';
 
@@ -10,6 +11,18 @@ void main() {
  testSetup();
 
  group('Computed', () {
+ test('toString', () {
+ final object = Computed(() {}, name: 'MyName');
+ expect(object.toString(), contains('MyName'));
+ });
+
+ test('debugCreationStack', () {
+ DebugCreationStack.enable = true;
+ addTearDown(() => DebugCreationStack.enable = false);
+ final object = Computed(() {});
+ expect(object.debugCreationStack, isNotNull);
+ });
+
  test('basics work', () {
  final x = Observable(20);
  final y = Observable(10);

mobx/test/observable_list_test.dart

@@ -627,6 +627,23 @@ void main() {
  '[]': (_) => _[0],
  '+': (_) => _ + [100],
  }.forEach(_templateReadTest);
+
+ test('bypass observable system', () {
+ final list = ObservableList<int>();
+
+ int? nonObservableInnerLength;
+ autorun(
+ (_) => nonObservableInnerLength = list.nonObservableInner.length);
+
+ expect(list.nonObservableInner.length, 0);
+ expect(nonObservableInnerLength, equals(0));
+
+ list.add(20);
+
+ expect(list.nonObservableInner.length, 1);
+ expect(nonObservableInnerLength, equals(0),
+ reason: 'should not be observable');
+ });
  });
  });
 

mobx/test/observable_map_test.dart

@@ -228,6 +228,22 @@ void main() {
 
  expect(map.containsKey('a'), isTrue);
  });
+
+ test('bypass observable system', () {
+ final map = ObservableMap<int, int>();
+
+ int? nonObservableInnerLength;
+ autorun((_) => nonObservableInnerLength = map.nonObservableInner.length);
+
+ expect(map.nonObservableInner.length, 0);
+ expect(nonObservableInnerLength, equals(0));
+
+ map[10] = 20;
+
+ expect(map.nonObservableInner.length, 1);
+ expect(nonObservableInnerLength, equals(0),
+ reason: 'should not be observable');
+ });
  });
 }
 

mobx/test/observable_set_test.dart

@@ -1,4 +1,5 @@
 import 'package:mobx/src/api/observable_collections.dart';
+import 'package:mobx/src/api/reaction.dart';
 import 'package:mobx/src/core.dart';
 import 'package:mocktail/mocktail.dart';
 import 'package:test/test.dart';
@@ -143,6 +144,22 @@ void main() {
  'retainWhere': (m) => m.retainWhere((i) => i < 3),
  }.forEach(runWriteTest);
  });
+
+ test('bypass observable system', () {
+ final set = ObservableSet<int>();
+
+ int? nonObservableInnerLength;
+ autorun((_) => nonObservableInnerLength = set.nonObservableInner.length);
+
+ expect(set.nonObservableInner.length, 0);
+ expect(nonObservableInnerLength, equals(0));
+
+ set.add(10);
+
+ expect(set.nonObservableInner.length, 1);
+ expect(nonObservableInnerLength, equals(0),
+ reason: 'should not be observable');
+ });
  });
 }
 

mobx/test/observable_test.dart

@@ -1,4 +1,5 @@
 import 'package:mobx/mobx.dart';
+import 'package:mobx/src/utils.dart';
 import 'package:mocktail/mocktail.dart' as mock;
 import 'package:test/test.dart';
 
@@ -12,6 +13,18 @@ void main() {
  testSetup();
 
  group('observable<T>', () {
+ test('toString', () {
+ final object = Observable(42, name: 'MyName');
+ expect(object.toString(), contains('MyName'));
+ });
+
+ test('debugCreationStack', () {
+ DebugCreationStack.enable = true;
+ addTearDown(() => DebugCreationStack.enable = false);
+ final object = Observable(42);
+ expect(object.debugCreationStack, isNotNull);
+ });
+
  test('basics work', () {
  final x = Observable<int?>(null);
  expect(x.value, equals(null));
@@ -59,6 +72,14 @@ void main() {
  () => context.endBatch()
  ]);
  });
+
+ test('nonObservableValue', () {
+ final x = Observable<int?>(null);
+ expect(x.nonObservableValue, null);
+
+ x.value = 100;
+ expect(x.nonObservableValue, 100);
+ });
  });
 
  group('createAtom()', () {