Fix Map/List/Set equality in generated Dart structs

[nightscape]

Generated Dart structs with collection fields (Map, List, Set) were using identity comparison (==) instead of deep equality. This caused equality checks to fail even when collection contents were identical.

Fix:

• Use DeepCollectionEquality for collection fields in operator== and hashCode
• Export DeepCollectionEquality from flutter_rust_bridge_for_generated_common.dart
• Handle Optional types wrapping collections

Changes

Fixes #the-issue-number-here

Procedure and Checklist

In order to quickly iterate and avoid slowing down development pace by making CI pass, only the following simplified steps are needed, and I (fzyzcjy) will handle the rest of CI / moving the tests currently (will have more automation in the future).

• Implement the feature / fix the bug.
• Add tests in frb_example/dart_minimal.
• Make dart_minimal's CI green.

Utility commands

• Run codegen: cargo run --manifest-path /path/to/flutter_rust_bridge/frb_codegen/Cargo.toml -- generate
• Run tests: ./frb_internal test-dart-native --package frb_example/dart_minimal

[Copilot]

Pull request overview

This pull request fixes a critical bug in generated Dart struct equality checking where collection fields (Map, List, Set) were using identity comparison (==) instead of deep equality comparison. This caused equality checks to fail even when collection contents were identical.

Key Changes:

• Modified code generation logic to use DeepCollectionEquality for collection fields in operator== and hashCode
• Added recursive handling for Optional types wrapping collections
• Exported DeepCollectionEquality from the common library for generated code

Reviewed changes

Copilot reviewed 29 out of 29 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
frb_codegen/src/library/codegen/generator/api_dart/spec_generator/class/ty/structure_non_freezed.rs	Core logic change: Added needs_deep_equality() function to detect collection types and generate appropriate equality/hash code using DeepCollectionEquality
frb_dart/lib/flutter_rust_bridge_for_generated_common.dart	Exported DeepCollectionEquality from collection package for use in generated code
frb_example/pure_dart/test/api/mirror_test.dart	Added tests verifying Map and List equality works correctly for structs with identical contents
frb_example/pure_dart/lib/src/rust/api/*.dart	Generated Dart code updated to use DeepCollectionEquality for List/Map/Set fields in equality and hashCode methods
frb_example/pure_dart/lib/src/rust/api/enumeration.dart	Code formatting changes (unrelated to equality fix)

---

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[Copilot]

The needs_deep_equality function does not handle MirType::Boxed types that wrap collections (List, Map, or Set). If a field has type Box<List<T>>, Box<Map<K,V>>, or Box<Set<T>>, the function will return false and use identity comparison instead of deep equality.

Consider adding a case for MirType::Boxed that recursively checks the inner type, similar to how MirType::Optional is handled.

Suggested change

	MirType::Optional(opt) => needs_deep_equality(&opt.inner),
	MirType::Optional(opt) => needs_deep_equality(&opt.inner),
	MirType::Boxed(_) => true,

[codecov]

Codecov Report

❌ Patch coverage is 85.00000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.19%. Comparing base (67bfaec) to head (f2a4601).

Files with missing lines	Patch %	Lines
...t/spec_generator/class/ty/structure_non_freezed.rs	85.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #2956       +/-   ##
===========================================
- Coverage   98.57%   85.19%   -13.39%     
===========================================
  Files         464      464               
  Lines       19202    18976      -226     
===========================================
- Hits        18928    16166     -2762     
- Misses        274     2810     +2536     

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[fzyzcjy]

Great job! However, this seems to be a breaking change, maybe we should add a flag to allow users to enable/disable it. In addition, it seems that users can use freezed to generate classes with deep equality.

[fzyzcjy]

/gemini review

[gemini-code-assist]

Code Review

This pull request aims to fix an issue where Dart structs with collection fields used identity comparison instead of deep equality. The approach of using DeepCollectionEquality from the collection package is correct and has been applied to the code generator for hashCode and operator==. The changes also include adding new tests to verify this fix for Map and List types. However, the implementation in the code generator is incomplete as it does not handle all collection types, such as primitive lists (e.g., Uint8List) and arrays. I've left a specific comment with a suggestion to address this.

[gemini-code-assist]

The needs_deep_equality function seems to be incomplete. It doesn't handle all collection types, which will lead to incorrect equality checks for structs containing them.

Specifically, it's missing:

• MirType::PrimitiveList(_): For typed data lists like Uint8List, Int32List, etc.
• MirTypeDelegate::Array(_): For fixed-size arrays.

These types, like other collections, are compared by identity by default in Dart, so they require deep equality checks for correctness. The DeepCollectionEquality from the collection package handles these cases correctly.

I suggest updating the function to include these types.

Suggested change

	fn needs_deep_equality(ty: &MirType) -> bool {
	match ty {
	MirType::GeneralList(_) => true,
	MirType::Delegate(delegate) => matches!(
	delegate,
	MirTypeDelegate::Map(_) | MirTypeDelegate::Set(_)
	),
	MirType::Optional(opt) => needs_deep_equality(&opt.inner),
	_ => false,
	}
	}
	fn needs_deep_equality(ty: &MirType) -> bool {
	match ty {
	MirType::GeneralList(_) | MirType::PrimitiveList(_) => true,
	MirType::Delegate(delegate) => matches!(
	delegate,
	MirTypeDelegate::Array(_) | MirTypeDelegate::Map(_) | MirTypeDelegate::Set(_)
	),
	MirType::Optional(opt) => needs_deep_equality(&opt.inner),
	_ => false,
	}
	}