many_lints 1.2.0

A comprehensive collection of custom lint rules, quick fixes, and code assists for Flutter and Dart projects.

example/README.md

many_lints Examples

This directory contains example code demonstrating every lint rule provided by many_lints. Each file in lib/ corresponds to one rule and marks the relevant bad and good cases. Most files trigger their named lint directly; the two path-based rules (match_lib_folder_structure and prefer_correct_test_file_name) use commented path examples because a flat lib/ file cannot violate either rule. Since the broad example preset is enabled, dart analyze example can also show related diagnostics from other rules.

Setup

Add to your analysis_options.yaml:

plugins:
  many_lints: ^1.2.0

Excluding paths per rule

many_lints.yaml in this directory demonstrates per-rule exclude:

rules:
  avoid_only_rethrow:
    exclude:
      - lib/excluded/**

lib/excluded/excluded_example.dart contains the same redundant catch clauses as lib/avoid_only_rethrow_example.dart, but reports nothing — that path is excluded for the rule. Delete many_lints.yaml and run dart analyze again to see the two diagnostics come back.

Note that avoid_commented_out_code does still report in that file. Each exclude sits under one rule and affects only that rule — excluding a path from avoid_only_rethrow says nothing about the other rules. To skip a path for several rules, give each of them its own exclude.

Paths are globs, but a plain path works too — lib/generated/foo.dart is a valid pattern, and you can list as many entries as you like:

rules:
  avoid_only_rethrow:
    exclude:
      - lib/legacy/parser.dart      # one specific file
      - lib/generated/**            # a whole directory tree
      - "**/*.g.dart"               # every generated file

The same rules: block can instead live under a top-level many_lints: key in analysis_options.yaml — the two forms are equivalent.

All Rules

Rule	Description	Fix
always_pass_global_key	Don't create a GlobalKey inside build.	—
always_remove_listener	Ensure every addListener() has a matching removeListener() in dispose().	Yes
arguments_ordering	Keep named arguments in a configured order.	—
async_value_nullable_pattern	Matching AsyncValue(:final value?) on a nullable value hides a legitimate null result.	Yes
avoid_accessing_collections_by_constant_index	Avoid accessing a collection by a constant index inside a loop.	—
avoid_accessing_other_classes_private_members	Make the underscore mean what everyone reads it as.	—
avoid_ad_hoc_left_type	A pipeline only composes when every step shares one error type.	—
avoid_banned_annotations	Ban specific annotations, optionally scoped by directory.	—
avoid_banned_exports	Ban re-exports of specific libraries, optionally scoped by directory.	—
avoid_banned_imports	Ban imports of specific libraries, optionally scoped by directory.	—
avoid_banned_names	Ban specific identifiers from being used as declaration names.	—
avoid_banned_types	Ban specific types from being named, optionally scoped by directory.	—
avoid_bare_await_in_do	Awaiting a raw Future inside a Do block escapes the block's tracking.	—
avoid_bloc_public_methods	Prevent public methods, getters, and setters in Bloc classes.	—
avoid_border_all	Use Border.fromBorderSide instead of Border.all for const support.	Yes
avoid_build_context_in_providers	Providers outlive widgets, so they should not receive a BuildContext.	—
avoid_cascade_after_if_null	Detect cascades after if-null operators without parentheses.	Yes
avoid_catch_error	Use try/catch instead of Future.catchError.	—
avoid_collapsible_if	Merge nested if statements with &&.	Yes
avoid_collection_equality_checks	Avoid comparing collections with == or != as it checks reference equality, not contents.	—
avoid_collection_methods_with_unrelated_types	Avoid calling collection methods with arguments whose types are unrelated to the collection's type parameter.	—
avoid_commented_out_code	Detect and flag commented-out code.	Yes
avoid_complex_conditions	Keep boolean conditions within an operand budget.	—
avoid_conditional_hooks	Never call hooks inside conditionals, loops, or ternaries.	—
avoid_constant_conditions	Detect comparisons where both sides are constants.	—
avoid_constant_switches	Detect switch statements on constant expressions.	—
avoid_contradictory_expressions	Detect logical AND conditions that always evaluate to false.	—
avoid_deep_nesting	Keep control flow within a nesting budget.	—
avoid_deep_widget_nesting	Keep a widget tree within a nesting budget.	—
avoid_default_tostring	Don't interpolate objects that don't override toString.	—
avoid_dollar_outside_do_frame	Calling a Do block's extraction function from a nested callback unwinds through code that cannot handle it.	—
avoid_dst_unsafe_date_arithmetic	Calendar day arithmetic on a local DateTime should not go through Duration.	Yes
avoid_duplicate_bloc_event_handlers	Register each bloc event type exactly once.	—
avoid_duplicate_cascades	Detect duplicate cascade sections in cascade expressions.	Yes
avoid_duplicate_collection_elements	Don't repeat the same element in a collection literal.	Yes
avoid_duplicate_mixins	Flag a mixin applied twice in one with clause.	—
avoid_either_of_future	A Future nested in Either or Option escapes the error channel.	—
avoid_empty_catch	Detect catch clauses that silently discard the failure.	—
avoid_empty_setstate	Don't call setState with an empty callback.	—
avoid_empty_spread	Remove spreads of empty collection literals.	Yes
avoid_equal_expressions	Both operands of a binary expression should not be identical.	—
avoid_exit_outside_entrypoint	Detect exit() outside the program entrypoint, which kills tests.	—
avoid_expanded_as_spacer	Use Spacer instead of Expanded with an empty child.	Yes
avoid_flexible_outside_flex	Only use Flexible and Expanded as direct children of Row, Column, or Flex.	—
avoid_focused_tests	Detect tests focused with solo:, which silences their siblings.	—
avoid_future_ignore	Do not silently suppress Future errors with an unexplained ignore call.	—
avoid_future_of_either	Future<Either> throws away the composition TaskEither already gives you.	—
avoid_future_of_option	Future<Option> throws away the composition TaskOption already gives you.	—
avoid_generics_shadowing	Avoid generic type parameters that shadow top-level declarations.	Yes
avoid_get_or_else_swallowing_failure	getOrElse is handed the failure; ignoring it should be a visible decision.	—
avoid_high_cyclomatic_complexity	Keep a function within a complexity budget.	—
avoid_hooks_outside_build	Only call hooks from a hook context.	—
avoid_incomplete_copy_with	Ensure copyWith methods include all constructor parameters.	Yes
avoid_inconsistent_digit_separators	Group digit separators at a regular interval.	Yes
avoid_incorrect_image_opacity	Use Image's opacity parameter instead of wrapping in Opacity.	Yes
avoid_inherited_widget_in_initstate	Don't look up inherited widgets inside initState.	—
avoid_inverted_boolean_checks	Use the opposite operator instead of negating a comparison.	Yes
avoid_late_context	Don't read BuildContext in a late field initializer.	—
avoid_late_final_reassignment	Flag a late final field assigned twice on one path.	—
avoid_long_files	Keep a file within a line budget.	—
avoid_long_functions	Keep function bodies within a line budget.	—
avoid_long_parameter_list	Keep parameter lists within a budget.	—
avoid_map_keys_contains	Use containsKey() instead of .keys.contains() for better performance.	Yes
avoid_missing_completer_stack_trace	Pass the stack trace to Completer.completeError.	—
avoid_missing_enum_constant_in_map	Cover every enum constant in a map keyed by that enum.	—
avoid_misused_hooks	Don't call hooks inside loops.	—
avoid_misused_test_matchers	Detect test matchers used with incompatible value types.	—
avoid_mounted_in_setstate	Detect mounted checks inside setState callbacks.	—
avoid_negated_conditions	State the positive case first in an if/else.	Yes
avoid_nested_conditional_expressions	Flag a conditional nested inside another.	—
avoid_nested_do_notation	A nested Do block short-circuits on its own instead of failing the outer pipeline.	—
avoid_nested_futures	Don't declare Future<Future<T>>.	—
avoid_nested_shorthands	Avoid nesting a dot shorthand inside another dot shorthand invocation.	—
avoid_non_null_assertion	Don't assert away null with the ! operator.	—
avoid_not_encodable_in_to_json	Don't put values jsonEncode cannot serialize into a toJson map.	—
avoid_notifier_constructors	Prevent initialization logic in Notifier constructors.	Yes
avoid_only_rethrow	Detect catch clauses that only rethrow the exception.	Yes
avoid_passing_async_when_sync_expected	Don't pass an async closure where a void-returning function is expected.	—
avoid_passing_bloc_to_bloc	Prevent Bloc/Cubit classes from depending on other Bloc/Cubit instances.	—
avoid_passing_build_context_to_blocs	Prevent passing BuildContext to Bloc or Cubit classes.	—
avoid_public_notifier_properties	Prevent public fields, getters, and setters on Notifier classes.	—
avoid_recursive_widget_calls	Don't build a widget from inside its own build method.	—
avoid_redundant_async	Flag an async function that never awaits.	—
avoid_redundant_else	Drop the else when the if branch always exits.	Yes
avoid_ref_inside_state_dispose	Avoid accessing ref inside the dispose method of a ConsumerState.	—
avoid_ref_read_inside_build	Subscribe in build; do not read once.	Yes
avoid_ref_watch_outside_build	Subscribe only in build; read once everywhere else.	—
avoid_removed_fpdart_api	Names removed in fpdart 1.0.0, with the replacement to use.	—
avoid_returning_widgets	Extract widget helper methods into separate widget classes.	—
avoid_self_compare	Flag a value compared against itself with compareTo.	—
avoid_shadowed_extension_methods	An extension member the extended type already has.	—
avoid_shrink_wrap_in_lists	Avoid using shrinkWrap in ListView for better scroll performance.	Yes
avoid_single_child_in_multi_child_widgets	Don't use Column, Row, or other multi-child widgets with only one child.	—
avoid_single_field_destructuring	Avoid destructuring a single field when direct property access is simpler.	Yes
avoid_skipped_tests	Detect tests, groups and libraries switched off in place.	—
avoid_state_constructors	Avoid constructors with logic in State classes.	Yes
avoid_throw_in_catch_block	Detect throw expressions inside catch blocks.	Yes
avoid_throw_in_fp_callback	A throw inside an fpdart callback escapes the error channel the pipeline is built to carry.	—
avoid_todo_comments	Detect TODO comments that reference no tracked issue.	—
avoid_too_many_methods	Keep a class within a method budget.	—
avoid_too_many_widgets_per_build	Keep one build method within a widget budget.	—
avoid_unassigned_stream_subscriptions	Ensure stream subscriptions are assigned to a variable for proper cancellation.	—
avoid_unmodified_loop_condition	A while loop whose condition the body can never change.	—
avoid_unnecessary_call	Invoke a function directly instead of through .call().	—
avoid_unnecessary_constructor	Remove a constructor identical to the default one.	—
avoid_unnecessary_consumer_widgets	Don't extend ConsumerWidget if you never use WidgetRef.	Yes
avoid_unnecessary_continue	Remove a continue that ends a loop body.	Yes
avoid_unnecessary_enum_prefix	Drop an enum name repeated in its own constants.	—
avoid_unnecessary_extends	Remove an explicit extends Object.	—
avoid_unnecessary_gesture_detector	Remove GestureDetector widgets that have no event handlers.	Yes
avoid_unnecessary_hook_widgets	Don't extend HookWidget if you never call any hooks.	Yes
avoid_unnecessary_negations	Collapse double negations.	Yes
avoid_unnecessary_option	An Option that is wrapped and immediately unwrapped earns nothing.	—
avoid_unnecessary_overrides	Detect overrides that only delegate to super.	Yes
avoid_unnecessary_return	Remove a bare return; that ends a void function.	—
avoid_unnecessary_setstate	Detect unnecessary setState calls in lifecycle methods.	Yes
avoid_unnecessary_stateful_widgets	Detect StatefulWidgets that have no mutable state.	Yes
avoid_unrelated_type_casts	Don't cast or type-test between unrelated types.	—
avoid_unremovable_callbacks_in_listeners	Don't pass an inline closure to addListener.	—
avoid_unrun_task	Discarding a lazy fpdart value silently skips the work it describes.	—
avoid_unsafe_collection_methods	Check for emptiness before using first, last, single or reduce.	—
avoid_untyped_safe_cast	safeCast without explicit type arguments infers dynamic and always succeeds.	—
avoid_unused_after_null_check	A variable null-checked but never used in the guarded branch.	—
avoid_wildcard_cases_with_enums	Keep exhaustiveness checking by listing enum cases explicitly.	—
avoid_wrapping_in_padding	Avoid wrapping widgets that support padding in a Padding widget.	Yes
banned_usage	Ban specific members, such as DateTime.now, optionally scoped by directory.	—
check_for_equals_in_render_object_setters	Compare before marking a RenderObject dirty.	—
check_is_not_closed_after_async_gap	Check isClosed before emitting state after an await.	—
dispose_fields	Ensure State fields with disposal methods are cleaned up in dispose().	Yes
dispose_provided_instances	Ensure disposable instances in Riverpod providers are cleaned up with ref.onDispose.	Yes
double_literal_format	Write double literals with exactly one leading zero and no redundant trailing zeros.	Yes
emit_new_bloc_state_instances	Emit a new state instance instead of the existing state object.	—
enum_constants_ordering	Keep enum constants in a configured order.	—
format_comment	Write comments as capitalised, terminated sentences.	—
format_test_name	Hold test descriptions to a house pattern.	—
function_always_returns_null	A nullable-returning function whose every path returns null.	—
function_always_returns_same_value	Flag a function whose every return yields the same constant.	—
handle_bloc_event_subclasses	Register a handler for every Bloc event subclass.	—
initializers_ordering	Keep constructor initializers in field order.	—
list_all_equatable_fields	Ensure all fields are listed in Equatable props.	Yes
map_keys_ordering	Keep map literal keys in a configured order.	—
match_class_name_pattern	Match class names against a regular expression.	—
match_getter_setter_field_names	Make a getter and setter pair use the same field.	—
match_lib_folder_structure	Keep folders under lib/ in lower_snake_case.	—
match_pattern	Match code against a project-supplied pattern and offer its replacement.	Yes
max_imports	Keep a file within an import budget.	—
max_statements	Keep a function within a statement budget.	—
member_ordering	Keep class members in a configured order.	—
missing_provider_scope	Flutter applications using Riverpod must have a ProviderScope at the root of the widget tree.	Yes
never_discard_build_context	Don't discard a BuildContext parameter with a wildcard.	Yes
no_equal_conditions	Flag an if/else-if chain that repeats a condition.	—
no_equal_switch_case	Flag two switch branches with identical bodies.	—
no_equal_then_else	Both branches of a condition are identical.	—
no_magic_number	Give a number a name when it carries a policy.	—
no_magic_string	Name a string once it is repeated.	—
notifier_build	Classes annotated with @riverpod must define a build method.	Yes
parameters_ordering	Keep named parameters in a configured order.	—
pass_existing_future_to_future_builder	Don't create a new Future inline inside FutureBuilder.	—
pass_existing_stream_to_stream_builder	Don't create a new Stream inline inside StreamBuilder.	—
pattern_fields_ordering	Keep pattern fields in a configured order.	—
prefer_abstract_final_static_class	Classes with only static members should be declared as abstract final.	Yes
prefer_add_all	Replace an add-only loop with addAll.	Yes
prefer_align_over_container	Use Align instead of Container when only alignment is set.	Yes
prefer_and_then	andThen says that the previous value is not used.	Yes
prefer_any_or_every	Use .any() or .every() instead of .where().isEmpty/.isNotEmpty.	Yes
prefer_async_callback	Use 'AsyncCallback' instead of 'Future<void> Function()'.	Yes
prefer_bloc_extensions	Use context.read/watch instead of BlocProvider.of or RepositoryProvider.of.	Yes
prefer_boolean_prefixes	Name booleans as questions.	—
prefer_center_over_align	Use Center instead of Align when alignment is center.	Yes
prefer_chain_either	chainEither lifts a synchronous Either step for you.	—
prefer_chaining_over_intermediate_run	Several .run() calls in one body are a chain that was never joined up.	—
prefer_class_destructuring	Use Dart 3 class destructuring when accessing multiple properties on the same object.	Yes
prefer_compute_over_isolate_run	Use 'compute()' instead of 'Isolate.run()' for web platform compatibility.	Yes
prefer_conditional_expressions	Collapse a two-way if/else into a conditional expression.	—
prefer_const_border_radius	Use BorderRadius.all(Radius.circular()) for const support.	Yes
prefer_constrained_box_over_container	Use ConstrainedBox instead of Container when only constraints is set.	Yes
prefer_container	Replace sequences of nested widgets with a single Container.	Yes
prefer_correct_callback_field_name	Name callbacks onSomething, the way Flutter does.	—
prefer_correct_edge_insets_constructor	Use the simplest EdgeInsets constructor for the given values.	Yes
prefer_correct_error_name	Name exception and error classes with the matching suffix.	—
prefer_correct_future_return_type	Expose async results as non-nullable Future values.	Yes
prefer_correct_handler_name	Name event handlers after the event they answer.	—
prefer_correct_identifier_length	Keep identifier length within bounds.	—
prefer_correct_json_casts	Cast JSON values to nullable types.	—
prefer_correct_setter_parameter_name	Use one parameter name in every setter.	—
prefer_correct_test_file_name	Name test files so the runner actually runs them.	—
prefer_correct_type_name	Keep type names within a sensible length and correctly capitalised.	—
prefer_declaring_const_constructor	Declare a const constructor where the class allows one.	—
prefer_do_notation	Deeply nested flatMap callbacks read flatter as a Do block.	—
prefer_early_return	Replace a body-wrapping if with an early-return guard.	Yes
prefer_enums_by_name	Use .byName() instead of .firstWhere() to look up enum values by name.	Yes
prefer_equatable_mixin	Prefer using EquatableMixin instead of extending Equatable.	Yes
prefer_expect_later	Use 'expectLater' instead of 'expect' when testing Futures.	Yes
prefer_explicit_function_type	Prefer explicit function type annotations over the bare 'Function' type.	Yes
prefer_explicit_parameter_names	Name the parameters of a function type.	—
prefer_explicit_type_arguments	Pin the type arguments of the APIs where inference surprises.	—
prefer_extracting_callbacks	Keep long callbacks out of the widget tree.	—
prefer_for_loop_in_children	Prefer collection-for syntax over functional list building in widget children.	Yes
prefer_from_nullable	A null check that builds an Option by hand is what Option.fromNullable is for.	Yes
prefer_from_predicate	A conditional guarding an Option is one Option.fromPredicate call.	Yes
prefer_getter_over_method	Make a no-argument value read a getter.	—
prefer_immediate_return	Return an expression directly instead of via a throwaway variable.	Yes
prefer_immutable_bloc_state	Ensure Bloc and Cubit state classes are annotated with @immutable.	Yes
prefer_immutable_state	Ensure classes named as state are annotated with @immutable.	Yes
prefer_iterable_of	Use List.of() / Set.of() instead of .from() for type-safe copies.	Yes
prefer_match_file_name	Name a file after the first public declaration in it.	—
prefer_moving_to_variable	Compute a repeated property or invocation chain once into a variable.	—
prefer_multi_bloc_provider	Use MultiBlocProvider, MultiBlocListener, or MultiRepositoryProvider instead of nesting.	Yes
prefer_named_parameters	Name parameters once there are more than a couple.	—
prefer_overriding_parent_equality	Override == and hashCode when the parent class overrides them.	Yes
prefer_padding_over_container	Use Padding instead of Container when only padding or margin is set.	Yes
prefer_prefixed_global_constants	Prefix public top-level constants.	—
prefer_primary_constructors	Prefer a primary constructor (Dart 3.13+) over a class of final fields plus a field-assigning constructor.	Yes
prefer_private_named_parameters	Prefer private named parameters (Dart 3.12+) over initializer-list boilerplate.	Yes
prefer_return_await	Detect missing await on returned Futures inside try-catch.	Yes
prefer_returning_condition	Return the condition instead of true/false branches.	—
prefer_returning_shorthands	Use dot shorthand constructors in expression function return values.	Yes
prefer_safe_collection_access	list.first throws where list.head returns None.	Yes
prefer_shorthands_with_constructors	Use dot shorthand constructors for common Flutter classes.	Yes
prefer_shorthands_with_enums	Use dot shorthands instead of explicit enum prefixes.	Yes
prefer_shorthands_with_static_fields	Use dot shorthands instead of explicit class prefixes for static fields.	Yes
prefer_simpler_patterns_null_check	Suggest simpler null-check patterns in if-case expressions.	Yes
prefer_single_declaration_per_file	Keep one top-level declaration per file, with per-type budgets.	—
prefer_single_setstate	Merge multiple setState calls into a single call.	Yes
prefer_single_widget_per_file	Keep one public widget per file for better organization.	—
prefer_sized_box_square	Use SizedBox.square when width and height are equal.	Yes
prefer_spacing	Use the spacing argument on Row/Column instead of SizedBox spacers.	—
prefer_string_parse_extensions	Option.fromNullable(int.tryParse(s)) is what toIntOption already is.	Yes
prefer_switch_expression	Suggest converting switch statements to switch expressions.	Yes
prefer_switch_with_enums	Use a switch instead of an if-else chain over enum constants.	—
prefer_task_either_over_try_catch	A repository's failures belong in its signature, not in a try/catch.	—
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 accessibility.	Yes
prefer_theme_mode_getters	Prefer ThemeMode.isDark/isLight/isSystem getters (Flutter 3.44+) over == comparisons.	Yes
prefer_transform_over_container	Use Transform instead of Container when only transform is set.	Yes
prefer_type_over_var	Prefer an explicit type annotation over 'var'.	Yes
prefer_typed_exceptions	Detect throws that give callers nothing to catch selectively.	—
prefer_typedefs_for_callbacks	Name a multi-parameter function type with a typedef.	—
prefer_unit_over_void	void is not a value, so an fpdart type parameterised with it stops composing.	Yes
prefer_use_callback	Use 'useCallback' instead of 'useMemoized' for memoizing functions.	Yes
prefer_use_prefix	Custom hooks should start with the 'use' prefix.	Yes
prefer_void_callback	Use 'VoidCallback' instead of 'void Function()'.	Yes
prefer_widget_private_members	A widget's public API is its constructor.	—
prefer_wildcard_pattern	Use the wildcard pattern '_' instead of 'Object()' for catch-all cases.	Yes
proper_super_calls	Enforce correct ordering of super lifecycle calls in State classes.	Yes
protected_notifier_properties	A Notifier's state, ref and future should not be used from outside the notifier.	—
provider_parameters	Family provider arguments must have stable equality, or the provider is recreated on every rebuild.	—
record_fields_ordering	Keep record named fields in a configured order.	—
require_atomic_async_updates	Re-read shared state after an await instead of writing back a stale value.	—
require_mirror_test	Detect libraries under lib/ with no matching test file.	—
use_class_prefix	Require a name prefix for classes deriving from a configured type.	Yes
use_class_suffix	Require a name suffix for classes deriving from a configured type.	Yes
use_closest_build_context	Use the inner BuildContext from builder callbacks, not the outer one.	Yes
use_dedicated_media_query_methods	Use MediaQuery.sizeOf(context) instead of MediaQuery.of(context).size.	Yes
use_existing_destructuring	Add properties to an existing destructuring instead of accessing them directly.	Yes
use_existing_variable	Use an existing variable instead of repeating its initializer expression.	Yes
use_gap	Use Gap widget instead of SizedBox for spacing in multi-child widgets.	Yes
use_ref_and_state_synchronously	Check ref.mounted before using ref or state after an await.	Yes
use_ref_read_synchronously	Add a mounted guard before calling ref.read after an await.	Yes
use_setstate_synchronously	Guard setState after an await with a mounted check.	—
use_sliver_prefix	Name widgets that return slivers with a Sliver prefix.	Yes

Detailed Examples

avoid_single_child_in_multi_child_widgets

Multi-child widgets like Column, Row, Wrap should not be used with only a single child.

❌ Bad:

Column(
  children: [Text('Only child')],
)

✅ Good:

Text('Only child')

---

avoid_unnecessary_consumer_widgets

ConsumerWidget should only be used when the WidgetRef is actually used.

❌ Bad:

class MyWidget extends ConsumerWidget {
  @override
  Widget build(BuildContext context, WidgetRef ref) {
    // ref is never used
    return Text('Hello');
  }
}

✅ Good:

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Text('Hello');
  }
}

---

avoid_unnecessary_hook_widgets

HookWidget should only be used when hooks are actually called.

❌ Bad:

class MyWidget extends HookWidget {
  @override
  Widget build(BuildContext context) {
    // No hooks called
    return Text('Hello');
  }
}

✅ Good:

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Text('Hello');
  }
}

---

prefer_align_over_container

Use Align widget instead of Container when only alignment is set.

❌ Bad:

Container(
  alignment: Alignment.topLeft,
  child: Text('Hello'),
)

✅ Good:

Align(
  alignment: Alignment.topLeft,
  child: Text('Hello'),
)

---

prefer_any_or_every

Use .any() instead of .where().isNotEmpty and .every() instead of .where().isEmpty.

❌ Bad:

final hasEven = numbers.where((n) => n.isEven).isNotEmpty;
final allPositive = numbers.where((n) => n < 0).isEmpty;

✅ Good:

final hasEven = numbers.any((n) => n.isEven);
final allPositive = numbers.every((n) => n >= 0);

---

prefer_center_over_align

Use Center widget instead of Align when alignment is center.

❌ Bad:

Align(
  alignment: Alignment.center,
  child: Text('Hello'),
)

✅ Good:

Center(
  child: Text('Hello'),
)

---

prefer_padding_over_container

Use Padding widget instead of Container when only margin is set.

❌ Bad:

Container(
  margin: EdgeInsets.all(16),
  child: Text('Hello'),
)

✅ Good:

Padding(
  padding: EdgeInsets.all(16),
  child: Text('Hello'),
)

---

The banned family

avoid_banned_imports, avoid_banned_exports, avoid_banned_types, avoid_banned_names, avoid_banned_annotations and banned_usage all read the same banned: entry shape and report nothing until configured — they enforce your policy, not a built-in one. See many_lints.yaml.

rules:
  avoid_banned_imports:
    banned:
      - deny: ['dart:io']              # exact match
        in: ['lib/domain/**']          # optional glob scope; omit for everywhere
        message: 'Keep the domain layer platform-independent.'
      - deny_pattern: ['package:legacy_.*']   # anchored to the whole value

Each entry takes deny and/or deny_pattern, plus optional in and message. deny matches exactly — banning async does not ban dart:async — so patterns are always opt-in.

❌ Bad:

// in lib/domain/user_repository.dart
import 'dart:io';

✅ Good:

// in lib/domain/user_repository.dart
abstract class ConfigSource {
  Future<String> read();
}

---

use_class_prefix

Requires a configured name prefix for classes deriving from a configured type. Reports nothing until configured — see many_lints.yaml.

rules:
  use_class_prefix:
    entries:
      - type: Repository
        prefix: Db

❌ Bad:

class UserRepository implements Repository {}

✅ Good:

class DbUserRepository implements Repository {}

---

use_class_suffix

Requires a configured name suffix for classes deriving from a configured type. Matches through extends, implements, with, or an indirect ancestor.

rules:
  use_class_suffix:
    entries:
      - type: Bloc
        package: bloc
        suffix: Bloc

❌ Bad:

class CounterManager extends Bloc<CounterEvent, int> {}

✅ Good:

class CounterBloc extends Bloc<CounterEvent, int> {}

---

use_dedicated_media_query_methods

Use dedicated MediaQuery methods to avoid unnecessary rebuilds.

❌ Bad:

final size = MediaQuery.of(context).size;
final padding = MediaQuery.of(context).padding;
final orientation = MediaQuery.of(context).orientation;

✅ Good:

final size = MediaQuery.sizeOf(context);
final padding = MediaQuery.paddingOf(context);
final orientation = MediaQuery.orientationOf(context);

---

use_gap

Use Gap widget instead of SizedBox or Padding for spacing in multi-child widgets.

❌ Bad:

Column(
  children: [
    Text('First'),
    SizedBox(height: 16),
    Text('Second'),
  ],
)

✅ Good:

Column(
  children: [
    Text('First'),
    Gap(16),
    Text('Second'),
  ],
)

---

Suppressing Diagnostics

To suppress a specific lint, use comments:

// ignore: many_lints/prefer_center_over_align
const example = Align(alignment: Alignment.center);

// ignore_for_file: many_lints/use_class_suffix

The many_lints/ prefix is required. Unlike SDK lints, a plugin diagnostic is only silenced when the rule name is prefixed with the plugin name, so a bare // ignore: prefer_center_over_align has no effect. The prefix is the key used under plugins: in analysis_options.yaml.

Suppressing by type is also possible via // ignore: type=lint (the type= form is required, and it silences every lint on that line, SDK ones included).

More Information

See the individual example files in lib/ for complete, runnable code samples.