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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][rules] are available,
checking anything from potential typing issues, coding style, and formatting.
This package, `lints`, contains the lint settings recommended by the Dart team.

Two sets of Dart lints are available:

* **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.

Finally, a third set [`flutter_lints`](https://pub.dev/packages/flutter_lints)
extends the recommended set with additional recommended Flutter-specific lints.

## Where these lints are used

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

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

For documentation on the individual lints, see the [linter rules][rules] page on
dart.dev.

## How to enable these lints

For new apps created with `dart create`, the lints are enabled by default.

For existing apps or packages, take these steps to enable these lints:

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

    ```terminal
    dart pub add --dev lints
    ```

2.  Create a new `analysis_options.yaml` file, next to the pubspec, that
    includes the lints package:

    ```yaml
    include: package:lints/recommended.yaml
    ```

    or:

    ```yaml
    include: package:lints/core.yaml
    ```

## Customizing the predefined lint sets

You can customize the predefined lint sets, both to disable one or more of the
lints included, or to add additional lints. For details see [customizing static
analysis].

## Migrating from `package:pedantic`

In migrating from the predefined lint sets provided by the [`package:pedantic`],
you get static analysis coverage from 29 additional lints. There are, however,
6 lints which the pedantic package includes which are not included in the
predefined lint sets provided by the lints package:
`always_declare_return_types`, `prefer_single_quotes`,
`sort_child_properties_last`, `unawaited_futures`, `unsafe_html`, and
`use_full_hex_values_for_flutter_colors` (also included in
[`package:flutter_lints`]). To keep any of these lints enabled,
add them to your [analysis options][customizing static analysis].

Additionally, `package:pedantic` provides the `unawaited` method for use with
`unawaited_futures`. With SDK version 2.14 this method is available in the
`dart:async` package, and this is now the recommended way to use it. Be sure to
mark the minimum SDK version of your package as `2.14` if you do so.

## 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 informal process we use is:

1.  Anyone can file an [issue] to discuss a potential change to a lint set. (A
    change here means adding or removing a lint from one or both sets. If you
    want to discuss implementing 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.

[dart create]: https://dart.dev/tools/dart-tool
[scoring]: https://pub.dev/help/scoring
[customizing static analysis]: https://dart.dev/guides/language/analysis-options
[rules]: https://dart.dev/tools/linter-rules
[pub.dev]: https://pub.dev
[issue]: https://github.com/dart-lang/lints/issues
[linter repo]: https://github.com/dart-lang/linter
[`package:pedantic`]: https://pub.dev/packages/pedantic
[`package:flutter_lints`]: https://pub.dev/packages/flutter_lints