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Official Dart lint rules. Defines the 'core' and 'recommended' set of lints suggested by the Dart team.

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Official Dart lint rules #

The Dart linter is a static analyzer for identifying possible problems in your Dart source code. More than a hundred linter rules are available, checking anything from potential typing issues, coding style, and formatting. This package - package:lints - contains the lint settings recommended by the Dart team.

Lint sets #

This package includes two sets of lints:

  • Core lints: Lints that help identify critical issues that are likely to lead to problems when running or consuming Dart code. All code should pass these lints.

  • Recommended lints: Lints that help identify additional issues that may lead to problems when running or consuming Dart code, and lints that enforce writing Dart using a single, idiomatic style and format. All code is encouraged to pass these lints. The recommended lints include all the core lints.

Additionally, a third lint set - package:flutter_lints - extends the recommended set with additional recommended Flutter-specific lints.

The Dart team will likely not provide recommendations past the core and recommended sets (e.g., a strict rule set). However, there are many such rule sets in the ecosystem (available at

Rule set authors: consider adding the lints topic to your pubspec to allow easier discovery (e.g., For more information about topics, see

Where these lints are used #

When creating new Dart project using the dart create command, the lints from package:lints are enabled by default.

When uploading a package to the package repository, packages are awarded pub points based on how many of the 'core' lints pass.

Enabling the lints #

For new apps created with dart create the recommended set of lints are enabled by default.

For existing apps or packages, you can enable these lints via:

  1. In a terminal, located at the root of your package, run this command:

    dart pub add --dev lints
  2. Create a new analysis_options.yaml file, next to the pubspec, that includes the lints package:

    include: package:lints/recommended.yaml


    include: package:lints/core.yaml

Customizing the predefined lint sets #

For details on customizing static analysis above and beyond the predefined lint sets, see customizing static analysis.

Evolving the lint sets #

The Dart language changes and the ecosystem continues to develop new best practices, so the lint sets must be periodically updated to reflect the best way we know to write Dart code. The process we use is:

  1. Anyone can file an issue to discuss a potential change to a lint set (i.e., adding or removing a lint from one or both sets; if you're proposing an entirely new lint, the place to suggest that is at the linter repo). Feedback is welcome from any Dart user.

  2. Periodically, a group of Dart and Flutter team members meet to review the suggestions and decide what to adopt.

  3. The lists are updated and a new version of the package is published.

Lint set contents #

Core lints #

To use these lints create an analysis_options.yaml file with: include: package:lints/core.yaml.

Lint Rules Description
avoid_empty_else Avoid empty else statements.
avoid_relative_lib_imports Avoid relative imports for files in lib/.
avoid_shadowing_type_parameters Avoid shadowing type parameters.
avoid_types_as_parameter_names Avoid types as parameter names.
await_only_futures Await only futures.
camel_case_extensions Name extensions using UpperCamelCase.
camel_case_types Name types using UpperCamelCase.
curly_braces_in_flow_control_structures DO use curly braces for all flow control structures.
depend_on_referenced_packages Depend on referenced packages.
empty_catches Avoid empty catch blocks.
file_names Name source files using lowercase_with_underscores.
hash_and_equals Always override hashCode if overriding ==.
iterable_contains_unrelated_type Invocation of Iterable
list_remove_unrelated_type Invocation of remove with references of unrelated types.
no_duplicate_case_values Don't use more than one case with same value.
non_constant_identifier_names Name non-constant identifiers using lowerCamelCase.
null_check_on_nullable_type_parameter Don't use null check on a potentially nullable type parameter.
package_prefixed_library_names Prefix library names with the package name and a dot-separated path.
prefer_generic_function_type_aliases Prefer generic function type aliases.
prefer_is_empty Use isEmpty for Iterables and Maps.
prefer_is_not_empty Use isNotEmpty for Iterables and Maps.
prefer_iterable_whereType Prefer to use whereType on iterable.
prefer_typing_uninitialized_variables Prefer typing uninitialized variables and fields.
provide_deprecation_message Provide a deprecation message, via @Deprecated("message").
unnecessary_overrides Don't override a method to do a super method invocation with the same parameters.
unrelated_type_equality_checks Equality operator == invocation with references of unrelated types.
valid_regexps Use valid regular expression syntax.
void_checks Don't assign to void.

To use these lints create an analysis_options.yaml file with: include: package:lints/recommended.yaml.

Lint Rules Description
annotate_overrides Annotate overridden members.
avoid_function_literals_in_foreach_calls Avoid using forEach with a function literal.
avoid_init_to_null Don't explicitly initialize variables to null.
avoid_null_checks_in_equality_operators Don't check for null in custom == operators.
avoid_renaming_method_parameters Don't rename parameters of overridden methods.
avoid_return_types_on_setters Avoid return types on setters.
avoid_returning_null_for_void Avoid returning null for void.
avoid_single_cascade_in_expression_statements Avoid single cascade in expression statements.
constant_identifier_names Prefer using lowerCamelCase for constant names.
control_flow_in_finally Avoid control flow in finally blocks.
empty_constructor_bodies Use ; instead of {} for empty constructor bodies.
empty_statements Avoid empty statements.
exhaustive_cases Define case clauses for all constants in enum-like classes.
implementation_imports Don't import implementation files from another package.
library_names Name libraries using lowercase_with_underscores.
library_prefixes Use lowercase_with_underscores when specifying a library prefix.
library_private_types_in_public_api Avoid using private types in public APIs.
no_leading_underscores_for_library_prefixes Avoid leading underscores for library prefixes.
no_leading_underscores_for_local_identifiers Avoid leading underscores for local identifiers.
null_closures Do not pass null as an argument where a closure is expected.
overridden_fields Don't override fields.
package_names Use lowercase_with_underscores for package names.
prefer_adjacent_string_concatenation Use adjacent strings to concatenate string literals.
prefer_collection_literals Use collection literals when possible.
prefer_conditional_assignment Prefer using ??= over testing for null.
prefer_contains Use contains for List and String instances.
prefer_equal_for_default_values Use = to separate a named parameter from its default value.
prefer_final_fields Private field could be final.
prefer_for_elements_to_map_fromIterable Prefer 'for' elements when building maps from iterables.
prefer_function_declarations_over_variables Use a function declaration to bind a function to a name.
prefer_if_null_operators Prefer using if null operators.
prefer_initializing_formals Use initializing formals when possible.
prefer_inlined_adds Inline list item declarations where possible.
prefer_interpolation_to_compose_strings Use interpolation to compose strings and values.
prefer_is_not_operator Prefer is! operator.
prefer_null_aware_operators Prefer using null aware operators.
prefer_spread_collections Use spread collections when possible.
prefer_void_to_null Don't use the Null type, unless you are positive that you don't want void.
recursive_getters Property getter recursively returns itself.
slash_for_doc_comments Prefer using /// for doc comments.
type_init_formals Don't type annotate initializing formals.
unnecessary_brace_in_string_interps Avoid using braces in interpolation when not needed.
unnecessary_const Avoid const keyword.
unnecessary_constructor_name Unnecessary .new constructor name.
unnecessary_getters_setters Avoid wrapping fields in getters and setters just to be "safe".
unnecessary_late Don't specify the late modifier when it is not needed.
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_nullable_for_final_variable_declarations Use a non-nullable type for a final variable initialized with a non-nullable value.
unnecessary_string_escapes Remove unnecessary backslashes in strings.
unnecessary_string_interpolations Unnecessary string interpolation.
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 Use rethrow to rethrow a caught exception.
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Official Dart lint rules. Defines the 'core' and 'recommended' set of lints suggested by the Dart team.

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