A useful collection of custom lints for Flutter & Dart projects. Uses the new analysis_server_plugin system for direct integration with dart analyze and IDEs.

Features

This package provides a set of custom lints to help you write better Flutter code.

Getting started

Requires Dart 3.10+ (Flutter 3.38+)

Add many_lints to the top-level plugins section in your analysis_options.yaml file (NOT under analyzer:):

plugins:
  many_lints: ^0.4.0

That's it — the analysis server will automatically download and resolve the plugin from pub.dev. There is no need to add it to your pubspec.yaml.

Local development

For local development or when using many_lints from a cloned repository, use the path option:

git clone https://github.com/Nikoro/many_lints.git /path/to/many_lints

plugins:
  many_lints:
    path: /path/to/many_lints

Note: Git dependencies are not directly supported by the plugin system. Clone the repository locally and use the path option instead.

Important: After any change to the plugins section, you must restart the Dart Analysis Server.

Configuring diagnostics

All rules are registered as warnings and enabled by default. You can enable or disable individual rules under the diagnostics key:

plugins:
  many_lints:
    version: ^0.4.0
    diagnostics:
      prefer_center_over_align: true
      use_bloc_suffix: false

Available Lints

All 100 lints are enabled by default as warnings.

• always_remove_listener: Listener added but never removed in dispose().
• avoid_accessing_collections_by_constant_index: Avoid accessing a collection by a constant index inside a loop.
• avoid_bloc_public_methods: Avoid declaring public members in Bloc classes. Use events via add instead.
• avoid_border_all: Prefer Border.fromBorderSide over Border.all.
• avoid_cascade_after_if_null: Cascade after if-null operator without parentheses can produce unexpected results.
• avoid_collection_equality_checks: Comparing collections with ==/!= checks reference equality, not contents.
• avoid_collection_methods_with_unrelated_types: Detects collection method calls with arguments unrelated to the collection's type.
• avoid_commented_out_code: Detects comments that look like commented-out code.
• avoid_conditional_hooks: Warns when hooks are called inside conditional branches.
• avoid_constant_conditions: Both sides of a comparison are constants, so the result is always the same.
• avoid_constant_switches: The switch expression is a constant, so the result is always the same.
• avoid_contradictory_expressions: Detects contradictory comparisons in && chains that always evaluate to false.
• avoid_duplicate_cascades: Detects duplicate cascade sections that indicate copy-paste errors.
• avoid_expanded_as_spacer: Prefer replacing Expanded with an empty child with Spacer.
• avoid_flexible_outside_flex: Flexible/Expanded should only be used as a direct child of Row, Column, or Flex.
• avoid_generics_shadowing: Warns when a generic type parameter shadows a top-level declaration in the same file.
• avoid_incomplete_copy_with: copyWith is missing constructor parameters.
• avoid_incorrect_image_opacity: Use Image's opacity parameter instead of wrapping it in an Opacity widget.
• avoid_map_keys_contains: Use containsKey() instead of .keys.contains().
• avoid_misused_test_matchers: Detects incompatible matcher usage with the actual value type.
• avoid_mounted_in_setstate: Checking mounted inside setState is too late and can lead to an exception.
• avoid_notifier_constructors: Avoid constructors with logic in Notifier classes.
• avoid_only_rethrow: Catch clause contains only a rethrow statement.
• avoid_passing_bloc_to_bloc: Avoid passing a Bloc/Cubit to another Bloc/Cubit.
• avoid_passing_build_context_to_blocs: Avoid passing BuildContext to a Bloc/Cubit.
• avoid_public_notifier_properties: Avoid public properties on Notifier classes other than state.
• avoid_ref_inside_state_dispose: Avoid accessing ref inside the dispose() method.
• avoid_ref_read_inside_build: Avoid using ref.read inside the build method.
• avoid_returning_widgets: Avoid returning widgets from functions, methods, or getters.
• avoid_shrink_wrap_in_lists: Avoid using shrinkWrap in ListView.
• avoid_single_child_in_multi_child_widgets: Avoid using a single child in widgets that can accept multiple children (e.g., Row, Column, Flex).
• avoid_single_field_destructuring: Avoid single-field destructuring. Use direct property access instead.
• avoid_state_constructors: Avoid constructors with logic in State classes.
• avoid_throw_in_catch_block: Avoid using throw inside a catch block.
• avoid_unassigned_stream_subscriptions: Stream subscription is not assigned to a variable.
• avoid_unnecessary_consumer_widgets: Ensures that a ConsumerWidget uses the ref parameter.
• avoid_unnecessary_gesture_detector: Detects GestureDetector with no event handlers.
• avoid_unnecessary_hook_widgets: Ensures that a HookWidget uses hooks.
• avoid_unnecessary_overrides: Detects method overrides that only call super without additional logic.
• avoid_unnecessary_overrides_in_state: Detects State method overrides that only call super without additional logic.
• avoid_unnecessary_setstate: Detects unnecessary calls to setState.
• avoid_unnecessary_stateful_widgets: Detects StatefulWidget with no mutable state. Consider using StatelessWidget.
• avoid_wrapping_in_padding: Avoid wrapping a widget in a Padding widget when it already has padding support.
• dispose_fields: Detects fields that are not disposed in dispose().
• dispose_provided_instances: Detects instances with a dispose method that are not disposed via ref.onDispose().
• prefer_abstract_final_static_class: Classes with only static members should be declared as abstract final.
• prefer_align_over_container: Enforces the use of Align over Container with only the alignment parameter.
• prefer_any_or_every: Prefer .any() or .every() over .where().isEmpty/.isNotEmpty.
• prefer_async_callback: Use AsyncCallback instead of Future<void> Function().
• prefer_bloc_extensions: Use context.read/context.watch instead of BlocProvider.of().
• prefer_center_over_align: Prefer Center over Align with alignment: Alignment.center.
• prefer_class_destructuring: Suggests using class destructuring for repeated property accesses.
• prefer_compute_over_isolate_run: Use compute() instead of Isolate.run() for web platform compatibility.
• prefer_const_border_radius: Prefer BorderRadius.all(Radius.circular()) over BorderRadius.circular().
• prefer_constrained_box_over_container: Use ConstrainedBox instead of Container with only the constraints parameter.
• prefer_container: Detects sequences of nested widgets that can be replaced with a single Container.
• prefer_contains: Use .contains() instead of .indexOf() compared to -1.
• prefer_correct_edge_insets_constructor: Use a simpler EdgeInsets constructor.
• prefer_enums_by_name: Use .byName() instead of .firstWhere() to access enum values by name.
• prefer_equatable_mixin: Prefer using EquatableMixin instead of extending Equatable.
• prefer_expect_later: Prefer expectLater when testing Futures.
• prefer_explicit_function_type: Prefer explicit return type and parameter list over bare Function type.
• prefer_for_loop_in_children: Prefer using a for-loop instead of functional list building.
• prefer_immutable_bloc_state: Bloc state classes should be annotated with @immutable.
• prefer_iterable_of: Prefer .of() instead of .from() for List, Set, and Map for compile-time type safety.
• list_all_equatable_fields: Warns when an Equatable class does not list all instance fields in props.
• prefer_multi_bloc_provider: Prefer MultiBlocProvider instead of multiple nested BlocProviders.
• prefer_overriding_parent_equality: Parent class overrides == and hashCode but this class does not.
• prefer_padding_over_container: Enforces the use of Padding over Container with only margin.
• prefer_return_await: Missing await on returned Future inside try-catch block.
• prefer_returning_shorthands: Prefer dot shorthands when the instance type matches the return type.
• prefer_shorthands_with_constructors: Prefer dot shorthands instead of explicit class instantiations.
• prefer_shorthands_with_enums: Prefer dot shorthands instead of explicit enum prefixes.
• prefer_shorthands_with_static_fields: Prefer dot shorthands instead of explicit class prefixes for static fields.
• prefer_simpler_patterns_null_check: Prefer simpler null-check patterns in if-case expressions.
• prefer_single_setstate: Multiple setState calls should be merged into a single call.
• prefer_single_widget_per_file: Only one public widget per file.
• prefer_sized_box_square: Use SizedBox.square instead of SizedBox with equal width and height.
• prefer_spacing: Prefer passing the spacing argument instead of using SizedBox.
• prefer_switch_expression: Prefer switch expressions over switch statements when possible.
• prefer_test_matchers: Prefer using a Matcher instead of a literal value in expect().
• prefer_text_rich: Use Text.rich instead of RichText for better text scaling and accessibility.
• prefer_use_callback: Use useCallback instead of useMemoized for memoizing functions.
• prefer_transform_over_container: Use Transform instead of Container with only the transform parameter.
• prefer_type_over_var: Prefer an explicit type annotation over var.
• prefer_use_prefix: Custom hooks should start with the use prefix.
• prefer_void_callback: Use VoidCallback instead of void Function().
• prefer_wildcard_pattern: Use the wildcard pattern _ instead of Object().
• proper_super_calls: Ensures super calls are placed correctly (first in initState, last in dispose).
• use_bloc_suffix: Enforces the use of the Bloc suffix for classes that extend Bloc.
• use_closest_build_context: Use the closest available BuildContext instead of the outer one.
• use_cubit_suffix: Enforces the use of the Cubit suffix for classes that extend Cubit.
• use_dedicated_media_query_methods: Enforces the use of dedicated MediaQuery methods instead of MediaQuery.of(context).
• use_existing_destructuring: Use existing destructuring instead of accessing properties directly.
• use_existing_variable: Detects expressions that duplicate the initializer of an existing variable.
• use_gap: Prefer Gap widget instead of SizedBox or Padding for spacing in multi-child widgets.
• use_notifier_suffix: Enforces the use of the Notifier suffix for classes that extend Notifier.
• use_ref_and_state_synchronously: Don't use ref or state after an async gap without checking ref.mounted.
• use_ref_read_synchronously: Avoid calling ref.read after an await point without checking if the widget is mounted.
• use_sliver_prefix: Widget returns a sliver but its name does not start with Sliver.

Quick fixes

The following rules include auto-fixable quick fixes (78 total):

• always_remove_listener
• avoid_border_all
• avoid_cascade_after_if_null
• avoid_commented_out_code
• avoid_duplicate_cascades
• avoid_expanded_as_spacer
• avoid_generics_shadowing
• avoid_incomplete_copy_with
• avoid_incorrect_image_opacity
• avoid_map_keys_contains
• avoid_notifier_constructors
• avoid_only_rethrow
• avoid_ref_read_inside_build
• avoid_single_field_destructuring
• avoid_state_constructors
• avoid_throw_in_catch_block
• avoid_unnecessary_consumer_widgets
• avoid_unnecessary_gesture_detector
• avoid_unnecessary_hook_widgets
• avoid_unnecessary_overrides
• avoid_unnecessary_overrides_in_state
• avoid_unnecessary_setstate
• avoid_unnecessary_stateful_widgets
• avoid_wrapping_in_padding
• dispose_fields
• dispose_provided_instances
• prefer_abstract_final_static_class
• prefer_align_over_container
• prefer_any_or_every
• prefer_async_callback
• prefer_bloc_extensions
• prefer_center_over_align
• prefer_class_destructuring
• prefer_compute_over_isolate_run
• prefer_const_border_radius
• prefer_constrained_box_over_container
• prefer_container
• prefer_contains
• prefer_correct_edge_insets_constructor
• prefer_enums_by_name
• prefer_equatable_mixin
• prefer_expect_later
• prefer_explicit_function_type
• prefer_for_loop_in_children
• prefer_immutable_bloc_state
• prefer_iterable_of
• list_all_equatable_fields
• prefer_multi_bloc_provider
• prefer_overriding_parent_equality
• prefer_padding_over_container
• prefer_return_await
• prefer_returning_shorthands
• prefer_shorthands_with_constructors
• prefer_shorthands_with_enums
• prefer_shorthands_with_static_fields
• prefer_simpler_patterns_null_check
• prefer_single_setstate
• prefer_sized_box_square
• prefer_switch_expression
• prefer_text_rich
• prefer_use_callback
• prefer_transform_over_container
• prefer_type_over_var
• prefer_use_prefix
• prefer_void_callback
• prefer_wildcard_pattern
• proper_super_calls
• use_bloc_suffix
• use_closest_build_context
• use_cubit_suffix
• use_dedicated_media_query_methods
• use_existing_destructuring
• use_existing_variable
• use_gap
• use_notifier_suffix
• use_ref_and_state_synchronously
• use_ref_read_synchronously
• use_sliver_prefix

Available Assists

• Convert to collection-for: Converts .map().toList() or .map().toSet() to collection-for syntax.

Suppressing Diagnostics

To suppress a specific lint, use comments:

// ignore: many_lints/prefer_center_over_align
const Align(...);

// ignore_for_file: many_lints/use_bloc_suffix

Example

See the example/ directory for a Flutter project that demonstrates every lint rule in action. Each file corresponds to a single rule and contains code that triggers the lint.

use_cubit_suffix

DO use Cubit suffix for your cubit names.

BAD:

class MyClass extends Cubit<bool> {}

GOOD:

class MyClassCubit extends Cubit<bool> {}