Allow a custom equals parameter for observable collections

[amondnet]

Describe the changes proposed in this Pull Request.

Allow a custom equals parameter for observable collections, like observable stream, observable and computed .

#771
#482

If the PR fixes a specific issue, reference the issue with Fixes #.

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Pull Request Checklist

• If the changes are being made to code, ensure the version in pubspec.yaml is updated.
• Increment the major/minor/patch/patch-count, depending on the complexity of change
• Add the necessary unit tests to ensure the coverage does not drop
• Update the Changelog to include all changes made in this PR, organized by version
• Run the melos run set_version command from the root directory
• Include the necessary reviewers for the PR
• Update the docs if there are any API changes or additions to functionality

[netlify]

👷 Deploy request for mobx pending review.

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Name	Link
🔨 Latest commit	d13d88d

[codecov]

Codecov Report

Merging #970 (d13d88d) into main (d14a27e) will decrease coverage by 0.62%.
Report is 3 commits behind head on main.
The diff coverage is 83.33%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #970      +/-   ##
==========================================
- Coverage   99.00%   98.38%   -0.62%     
==========================================
  Files          57       57              
  Lines        2005     2043      +38     
==========================================
+ Hits         1985     2010      +25     
- Misses         20       33      +13     

Flag	Coverage Δ
flutter_mobx	100.00% <ø> (ø)
mobx	97.69% <83.33%> (-0.88%)	⬇️
mobx_codegen	100.00% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
...rc/api/observable_collections/observable_list.dart	99.20% <90.00%> (-0.80%)	⬇️
...src/api/observable_collections/observable_map.dart	98.41% <89.47%> (-1.59%)	⬇️
...src/api/observable_collections/observable_set.dart	91.17% <76.92%> (-8.83%)	⬇️

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[Copilot]

Pull Request Overview

This PR allows custom equality functions to be specified for MobX observable collections (ObservableList, ObservableMap, and ObservableSet). This enables developers to define custom comparison logic for determining when values are considered equal, which can optimize change detection and support custom equality semantics.

• Adds EqualityComparer<T>? equals parameter to all observable collection constructors
• Implements custom equality logic in value comparison operations for all three collection types
• Updates cast methods to preserve custom equality functions with optional overrides

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
mobx/test/observable_collections_equals_test.dart	Comprehensive test suite covering custom equals functionality across all collection types
mobx/pubspec.yaml	Version bump from 2.5.0 to 2.6.0 for minor feature addition
mobx/lib/version.dart	Updates version constant to match pubspec
mobx/lib/src/api/observable_collections/observable_set.dart	Implements custom equals support for ObservableSet with updated constructors and equality logic
mobx/lib/src/api/observable_collections/observable_map.dart	Adds custom equals parameter for value comparisons in ObservableMap
mobx/lib/src/api/observable_collections/observable_list.dart	Integrates custom equals functionality into ObservableList operations
mobx/lib/src/api/observable_collections.dart	Adds required imports for collection package and utils
mobx/CHANGELOG.md	Documents the new custom equals feature in version 2.6.0

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[Copilot]

The type check value is T? is incorrect for non-nullable types T. When T is non-nullable (e.g., String), T? becomes String?, but value with type Object? cannot be checked against T? directly. This should use value is T to check if value can be cast to the non-nullable type T.

Suggested change

	if (value is T?) {
	if (value is T) {

[Copilot]

Unsafe casting from R? to T? without type checking. If R and T are incompatible types, this will cause a runtime exception. Should add type compatibility checks or use a safer casting approach.

Suggested change

	? (R? a, R? b) => _equals!(a as T?, b as T?)
	? (R? a, R? b) {
	if (a is T? && b is T?) {
	return _equals!(a, b);
	}
	return false;
	}

[Copilot]

Unsafe casting from RV? to V? without type checking. If RV and V are incompatible types, this will cause a runtime exception. Should add type compatibility checks or use a safer casting approach.

Suggested change

	: (RV? a, RV? b) => _equals!(a as V?, b as V?)));
	: (RV? a, RV? b) {
	if (a is V? && b is V?) {
	return _equals!(a, b);
	}
	// If types are incompatible, consider them not equal
	return false;
	}));

[Copilot]

Unsafe casting from R? to T? without type checking. If R and T are incompatible types, this will cause a runtime exception. Should add type compatibility checks or use a safer casting approach.

Suggested change

	: (R? a, R? b) => _equals!(a as T?, b as T?)));
	: (R? a, R? b) {
	if (a is! T || b is! T) return false;
	return _equals!(a as T?, b as T?);
	}));