feat(bloc_lint): add prefer_multi_bloc_listener and prefer_multi_repository_provider - #4852

Status

READY

Breaking Changes

NO

Description

Adds two lint rules which warn when BlocListener or RepositoryProvider widgets are nested through the child argument, where a single MultiBlocListener / MultiRepositoryProvider is equivalent and easier to read.

// BAD
BlocListener<BlocA, BlocAState>(
  listener: (context, state) {},
  child: BlocListener<BlocB, BlocBState>(
    listener: (context, state) {},
    child: ChildA(),
  ),
);

// GOOD
MultiBlocListener(
  listeners: [
    BlocListener<BlocA, BlocAState>(listener: (context, state) {}),
    BlocListener<BlocB, BlocBState>(listener: (context, state) {}),
  ],
  child: ChildA(),
);

Implementation notes

Both rules are thin wrappers over a shared NestedWidgetListener (lib/src/nested_widget_listener.dart), parameterized by the widget name and its replacement.

• Maintains a stack of the enclosing argument lists, recording for each whether it belongs to the watched widget and whether it sits in a child slot. A report fires only when the immediately enclosing invocation is the same widget, so a widget that merely has a matching ancestor higher up the tree is not flagged.
• Only the outermost widget of a contiguous nested chain is reported, so a chain of three produces one diagnostic rather than two. Where the chain is broken by an unrelated callback, the innermost valid chain root is reported instead — both behaviours are covered by tests.
• Resolves type arguments via endTypeArguments and named constructors via the preceding ., so BlocListener<A, B>(...), RepositoryProvider(...) and RepositoryProvider<A>.value(...) are all recognized.
• Severity is info, matching the other prefer_* rules. These are readability rules — the two forms are equivalent at runtime, as the MultiBlocListener docs note.

Adding prefer_multi_bloc_provider (#4453) on top of this is a ~20 line change, should you want it — I left it out since that issue is assigned.

Verified locally against the CI gates: dart format, dart analyze --fatal-warnings lib test, full suite (172 tests, 21 new) and 100% coverage.

Closes #4454
Closes #4455

Type of Change

• ✨ New feature (non-breaking change which adds functionality)
• 🛠️ Bug fix (non-breaking change which fixes an issue)
• ❌ Breaking change (fix or feature that would cause existing functionality to change)
• 🧹 Code refactor
• ✅ Build configuration change
• 📝 Documentation
• 🗑️ Chore