From c17b55170a35fa24d2c2a925a55bc2040c6a2b05 Mon Sep 17 00:00:00 2001
From: Minsu Lee <amond@amond.net>
Date: Thu, 2 Nov 2023 23:30:52 +0900
Subject: [PATCH] Avoid unnecessary observable notifications of `Iterable` or
 `Map` fields

---
 mobx/lib/src/core/atom_extensions.dart | 21 +++------------------
 mobx/lib/src/core/observable.dart      |  2 +-
 mobx/lib/src/utils.dart                | 18 ++++++++++++++++++
 3 files changed, 22 insertions(+), 19 deletions(-)

diff --git a/mobx/lib/src/core/atom_extensions.dart b/mobx/lib/src/core/atom_extensions.dart
index 936fed7b0..b532b4236 100644
--- a/mobx/lib/src/core/atom_extensions.dart
+++ b/mobx/lib/src/core/atom_extensions.dart
@@ -1,6 +1,7 @@
-import 'package:collection/collection.dart';
 import 'package:mobx/mobx.dart';
 
+import '../utils.dart';
+
 extension AtomSpyReporter on Atom {
   void reportRead() {
     context.enforceReadPolicy(this);
@@ -10,7 +11,7 @@ extension AtomSpyReporter on Atom {
   void reportWrite<T>(T newValue, T oldValue, void Function() setNewValue,
       {EqualityComparer<T>? equals}) {
     final areEqual = equals == null
-        ? _equals(oldValue, newValue)
+        ? equatable(oldValue, newValue)
         : equals(oldValue, newValue);
 
     // Avoid unnecessary observable notifications of @observable fields of Stores
@@ -33,19 +34,3 @@ extension AtomSpyReporter on Atom {
     context.spyReport(EndedSpyEvent(type: 'observable', name: name));
   }
 }
-
-/// Determines whether [a] and [b] are equal.
-bool _equals<T>(T a, T b) {
-  if (identical(a, b)) return true;
-  if (a is Iterable || a is Map) {
-    if (!_equality.equals(a, b)) return false;
-  } else if (a.runtimeType != b.runtimeType) {
-    return false;
-  } else if (a != b) {
-    return false;
-  }
-
-  return true;
-}
-
-const DeepCollectionEquality _equality = DeepCollectionEquality();
diff --git a/mobx/lib/src/core/observable.dart b/mobx/lib/src/core/observable.dart
index a29230479..70290a094 100644
--- a/mobx/lib/src/core/observable.dart
+++ b/mobx/lib/src/core/observable.dart
@@ -105,7 +105,7 @@ class Observable<T> extends Atom
     }
 
     final areEqual =
-        equals == null ? prepared == value : equals!(prepared, _value);
+        equals == null ? equatable(prepared, value) : equals!(prepared, _value);
 
     return (!areEqual) ? prepared : WillChangeNotification.unchanged;
   }
diff --git a/mobx/lib/src/utils.dart b/mobx/lib/src/utils.dart
index cd81d806b..80c30b828 100644
--- a/mobx/lib/src/utils.dart
+++ b/mobx/lib/src/utils.dart
@@ -1,5 +1,7 @@
 import 'dart:async';
 
+import 'package:collection/collection.dart' show DeepCollectionEquality;
+
 const Duration ms = Duration(milliseconds: 1);
 
 Timer Function(void Function()) createDelayedScheduler(int delayMs) =>
@@ -20,3 +22,19 @@ mixin DebugCreationStack {
     return result;
   }();
 }
+
+/// Determines whether [a] and [b] are equal.
+bool equatable<T>(T a, T b) {
+  if (identical(a, b)) return true;
+  if (a is Iterable || a is Map) {
+    if (!_equality.equals(a, b)) return false;
+  } else if (a.runtimeType != b.runtimeType) {
+    return false;
+  } else if (a != b) {
+    return false;
+  }
+
+  return true;
+}
+
+const DeepCollectionEquality _equality = DeepCollectionEquality();