Linter for Dart

Lint Rules

View the Project on GitHub dartlang/linter

Supported Lint Rules

This list is auto-generated from our sources.

Rules are organized into familiar rule groups.

In addition, rules can be further distinguished by maturity. Unqualified rules are considered stable, while others may be marked experimental to indicate that they are under review. Lints that are marked as deprecated should not be used and are subject to removal in future Linter releases.

Rules can be selectively enabled in the analyzer using analysis options or through an analysis options file.

As some lints may contradict each other, only a subset of these will be enabled in practice, but this list should provide a convenient jumping-off point.

These rules are under active development. Feedback is welcome!

Error Rules

avoid_empty_else
flutter pedantic

Avoid empty else statements.

avoid_relative_lib_imports
pedantic

Avoid relative imports for files in lib/.

avoid_returning_null_for_future

Avoid returning null for Future.

avoid_slow_async_io

Avoid slow async dart:io methods.

avoid_types_as_parameter_names
pedantic

Avoid types as parameter names.

cancel_subscriptions
flutter

Cancel instances of dart.async.StreamSubscription.

close_sinks
flutter

Close instances of dart.core.Sink.

comment_references

Only reference in scope identifiers in doc comments.

control_flow_in_finally
flutter

Avoid control flow in finally blocks.

empty_statements
flutter

Avoid empty statements.

hash_and_equals
flutter

Always override hashCode if overriding ==.

invariant_booleans

Conditions should not unconditionally evaluate to true or to false.

iterable_contains_unrelated_type

Invocation of Iterable.contains with references of unrelated types.

list_remove_unrelated_type

Invocation of remove with references of unrelated types.

literal_only_boolean_expressions

Boolean expression composed only with literals.

no_adjacent_strings_in_list

Don't use adjacent strings in list.

no_duplicate_case_values
pedantic

Don't use more than one case with same value.

prefer_void_to_null

Don't use the Null type, unless you are positive that you don't want void.

test_types_in_equals
flutter

Test type arguments in operator ==(Object other).

throw_in_finally
flutter

Avoid throw in finally block.

unnecessary_statements
flutter

Avoid using unnecessary statements.

unrelated_type_equality_checks
flutter pedantic

Equality operator == invocation with references of unrelated types.

valid_regexps
flutter pedantic

Use valid regular expression syntax.

Style Rules

always_declare_return_types

Declare method return types.

always_put_control_body_on_new_line

Separate the control structure expression from its statement.

always_put_required_named_parameters_first

Put @required named parameters first.

always_require_non_null_named_parameters

Use @required.

always_specify_types

Specify type annotations.

annotate_overrides

Annotate overridden members.

avoid_annotating_with_dynamic

Avoid annotating with dynamic when not required.

avoid_as

Avoid using as.

avoid_bool_literals_in_conditional_expressions

Avoid bool literals in conditional expressions.

avoid_catches_without_on_clauses

Avoid catches without on clauses.

avoid_catching_errors

Don't explicitly catch Error or types that implement it.

avoid_classes_with_only_static_members

Avoid defining a class that contains only static members.

avoid_double_and_int_checks

Avoid double and int checks.

avoid_field_initializers_in_const_classes

Avoid field initializers in const classes.

avoid_function_literals_in_foreach_calls

Avoid using forEach with a function literal.

avoid_implementing_value_types

Don't implement classes that override ==.

avoid_init_to_null
flutter pedantic

Don't explicitly initialize variables to null.

avoid_js_rounded_ints

Avoid JavaScript rounded ints.

avoid_null_checks_in_equality_operators

Don't check for null in custom == operators.

avoid_positional_boolean_parameters

Avoid positional boolean parameters.

avoid_private_typedef_functions

Avoid private typedef functions.

avoid_renaming_method_parameters

Don't rename parameters of overridden methods.

avoid_return_types_on_setters
flutter pedantic

Avoid return types on setters.

avoid_returning_null

Avoid returning null from members whose return type is bool, double, int, or num.

avoid_returning_null_for_void

Avoid returning null for void.

avoid_returning_this

Avoid returning this from methods just to enable a fluent interface.

avoid_setters_without_getters

Avoid setters without getters.

avoid_shadowing_type_parameters

Avoid shadowing type parameters.

avoid_single_cascade_in_expression_statements

Avoid single cascade in expression statements.

avoid_types_on_closure_parameters

Avoid annotating types for function expression parameters.

avoid_unused_constructor_parameters

Avoid defining unused parameters in constructors.

avoid_void_async

Avoid async functions that return void.

await_only_futures
flutter

Await only futures.

camel_case_types
flutter

Name types using UpperCamelCase.

cascade_invocations

Cascade consecutive method invocations on the same reference.

constant_identifier_names

Prefer using lowerCamelCase for constant names.

curly_braces_in_flow_control_structures

DO use curly braces for all flow control structures.

directives_ordering

Adhere to Effective Dart Guide directives sorting conventions.

empty_catches

Avoid empty catch blocks.

empty_constructor_bodies
flutter

Use ; instead of {} for empty constructor bodies.

file_names

Name source files using lowercase_with_underscores.

flutter_style_todos

Use Flutter TODO format: // TODO(username): message, https://URL-to-issue.

implementation_imports
flutter

Don't import implementation files from another package.

join_return_with_assignment

Join return statement with assignment when possible.

library_names
flutter

Name libraries using lowercase_with_underscores.

library_prefixes

Use lowercase_with_underscores when specifying a library prefix.

lines_longer_than_80_chars

AVOID lines longer than 80 characters.

non_constant_identifier_names
flutter

Name non-constant identifiers using lowerCamelCase.

null_closures
pedantic

Do not pass null as an argument where a closure is expected.

omit_local_variable_types

Omit type annotations for local variables.

one_member_abstracts

Avoid defining a one-member abstract class when a simple function will do.

only_throw_errors

Only throw instances of classes extending either Exception or Error.

overridden_fields

Don't override fields.

package_api_docs
flutter

Provide doc comments for all public APIs.

package_prefixed_library_names
flutter

Prefix library names with the package name and a dot-separated path.

parameter_assignments

Don't reassign references to parameters of functions or methods.

prefer_adjacent_string_concatenation

Use adjacent strings to concatenate string literals.

prefer_asserts_in_initializer_lists

Prefer putting asserts in initializer list.

prefer_bool_in_asserts (deprecated)

Prefer using a boolean as the assert condition.

prefer_collection_literals

Use collection literals when possible.

prefer_conditional_assignment

Prefer using ??= over testing for null.

prefer_const_constructors

Prefer const with constant constructors.

prefer_const_constructors_in_immutables

Prefer declare const constructors on @immutable classes.

prefer_const_declarations

Prefer const over final for declarations.

prefer_const_literals_to_create_immutables

Prefer const literals as parameters of constructors on @immutable classes.

prefer_constructors_over_static_methods

Prefer defining constructors instead of static methods to create instances.

prefer_contains
pedantic

Use contains for List and String instances.

prefer_equal_for_default_values
pedantic

Use = to separate a named parameter from its default value.

prefer_expression_function_bodies

Use => for short members whose body is a single return statement.

prefer_final_fields

Private field could be final.

prefer_final_locals

Prefer final for variable declaration if reference is not reassigned.

prefer_foreach

Use forEach to only apply a function to all the elements.

prefer_function_declarations_over_variables

Use a function declaration to bind a function to a name.

prefer_generic_function_type_aliases

Prefer generic function type aliases.

prefer_initializing_formals

Use initializing formals when possible.

prefer_int_literals

Prefer int literals over double literals.

prefer_interpolation_to_compose_strings

Use interpolation to compose strings and values.

prefer_is_empty
pedantic

Use isEmpty for Iterables and Maps.

prefer_is_not_empty
flutter pedantic

Use isNotEmpty for Iterables and Maps.

prefer_iterable_whereType

Prefer to use whereType on iterable.

prefer_mixin

Prefer using mixins.

prefer_single_quotes

Prefer single quotes where they won't require escape sequences.

prefer_typing_uninitialized_variables

Prefer typing uninitialized variables and fields.

public_member_api_docs

Document all public members.

recursive_getters
pedantic

Property getter recursively returns itself.

slash_for_doc_comments
flutter

Prefer using /// for doc comments.

sort_constructors_first

Sort constructor declarations before other members.

sort_unnamed_constructors_first

Sort unnamed constructor declarations first.

super_goes_last
flutter

Place the super call last in a constructor initialization list.

type_annotate_public_apis

Type annotate public APIs.

type_init_formals
flutter

Don't type annotate initializing formals.

unawaited_futures
pedantic

Future results in async function bodies must be awaited or marked unawaited using package:pedantic.

unnecessary_await_in_return

Unnecessary await keyword in return.

unnecessary_brace_in_string_interps
flutter

Avoid using braces in interpolation when not needed.

unnecessary_const

Avoid const keyword.

unnecessary_getters_setters
flutter

Avoid wrapping fields in getters and setters just to be "safe".

unnecessary_lambdas

Don't create a lambda when a tear-off will do.

unnecessary_new

Unnecessary new keyword.

unnecessary_null_aware_assignments

Avoid null in null-aware assignment.

unnecessary_null_in_if_null_operators

Avoid using null in if null operators.

unnecessary_overrides

Don't override a method to do a super method invocation with the same parameters.

unnecessary_parenthesis

Unnecessary parenthesis can be removed.

unnecessary_this

Don't access members with this unless avoiding shadowing.

use_function_type_syntax_for_parameters

Use generic function type syntax for parameters.

use_rethrow_when_possible
pedantic

Use rethrow to rethrow a caught exception.

use_setters_to_change_properties

Use a setter for operations that conceptually change a property.

use_string_buffers

Use string buffer to compose strings.

use_to_and_as_if_applicable

Start the name of the method with to/_to or as/_as if applicable.

void_checks

Don't assign to void.

Pub Rules

package_names
flutter

Use lowercase_with_underscores for package names.

sort_pub_dependencies

Sort pub dependencies.