Dart & Flutter Equatable Engineering

Goal

Treat Equatable as an implementation mechanism for an already-defined equality model.

Do not begin with extends Equatable. First determine:

1. what the type represents;
2. whether separately constructed instances should be interchangeable;
3. which fields define that logical value;
4. whether equality must remain stable for the object's lifetime;
5. whether Bloc, selectors, caches, sets, maps, or tests rely on that equality;
6. which single equality mechanism best represents the semantics. Optimize for correctness first. Equality mistakes can silently alter state emission, rebuild behavior, cache keys, map/set lookup, deduplication, and tests.

Research baseline and freshness guard

The bundled source is based on Equatable 2.1.0 behavior, Dart equality documentation, and current Bloc/flutter_bloc behavior from that research baseline.