Mimic React Hook's dependencies comparison (#374)

closes #155

This PR changes the comparison behavior to mimic the React Hook dependencies comparison which uses Object.is().

Previously, keys are compared by the == operator. The Dart == operator works differently from the JavaScript Object.is():

Object.is()

Object.is(NaN, NaN) // true
Object.is(0, -0) // false
Dart ==

double.nan == double.nan // false
0 == -0 // true
This PR checks if a list of keys contain a value with the type num and proceeds to handle cases where the value is either NaN or 0.0 and -0.0.

packages/flutter_hooks/CHANGELOG.md

@@ -1,5 +1,8 @@
-## Unreleased minor
+## Unreleased major
 
+- **Breaking**: `keys` comparison has changed under the following conditions:
+  - Change from `double.nan` to `double.nan` preserves the state.
+  - Change from `0.0` to `-0.0` or vice versa does NOT preserve the state.
 - Added `useOnStreamChange` (thanks to @jezsung)
 
 ## 0.19.0 - 2023-07-10

packages/flutter_hooks/lib/src/framework.dart

@@ -153,6 +153,10 @@ Calling them outside of build method leads to an unstable state and is therefore
   ///
   /// - `hook1.keys == hook2.keys` (typically if the list is immutable)
   /// - If there's any difference in the content of [Hook.keys], using `operator==`.
+  ///
+  /// There are exceptions when comparing [Hook.keys] before using `operator==`:
+  /// - A state is preserved when one of the [Hook.keys] is [double.nan].
+  /// - A state is NOT preserved when one of the [Hook.keys] is changed from 0.0 to -0.0.
   static bool shouldPreserveState(Hook<Object?> hook1, Hook<Object?> hook2) {
     final p1 = hook1.keys;
     final p2 = hook2.keys;
@@ -172,7 +176,23 @@ Calling them outside of build method leads to an unstable state and is therefore
       if (!i1.moveNext() || !i2.moveNext()) {
         return true;
       }
-      if (i1.current != i2.current) {
+
+      final curr1 = i1.current;
+      final curr2 = i2.current;
+
+      if (curr1 is num && curr2 is num) {
+        // Checks if both are NaN
+        if (curr1.isNaN && curr2.isNaN) {
+          return true;
+        }
+
+        // Checks if one is 0.0 and the other is -0.0
+        if (curr1 == 0 && curr2 == 0) {
+          return curr1.isNegative == curr2.isNegative;
+        }
+      }
+
+      if (curr1 != curr2) {
         return false;
       }
     }

packages/flutter_hooks/test/use_effect_test.dart

@@ -249,6 +249,55 @@ void main() {
     verifyNoMoreInteractions(disposerA);
     verifyNoMoreInteractions(effect);
   });
+
+  testWidgets(
+      'does NOT call effect when one of keys is NaN and others are same',
+      (tester) async {
+    parameters = [double.nan];
+    await tester.pumpWidget(builder());
+
+    verifyInOrder([
+      effect(),
+      unrelated(),
+    ]);
+    verifyNoMoreInteractions(effect);
+
+    parameters = [double.nan];
+    await tester.pumpWidget(builder());
+
+    verifyNoMoreInteractions(effect);
+  });
+
+  testWidgets(
+      'calls effect when one of keys is changed from 0.0 to -0.0 and vice versa',
+      (tester) async {
+    parameters = [0.0];
+    await tester.pumpWidget(builder());
+
+    verifyInOrder([
+      effect(),
+      unrelated(),
+    ]);
+    verifyNoMoreInteractions(effect);
+
+    parameters = [-0.0];
+    await tester.pumpWidget(builder());
+
+    verifyInOrder([
+      effect(),
+      unrelated(),
+    ]);
+    verifyNoMoreInteractions(effect);
+
+    parameters = [0.0];
+    await tester.pumpWidget(builder());
+
+    verifyInOrder([
+      effect(),
+      unrelated(),
+    ]);
+    verifyNoMoreInteractions(effect);
+  });
 }
 
 class MockEffect extends Mock {