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An opinionated formatter/linter for Dart code

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Statistics on dart_style

Number of watchers on Github 144
Number of open issues 48
Average time to close an issue about 1 month
Main language Dart
Average time to merge a PR 2 days
Open pull requests 4+
Closed pull requests 8+
Last commit about 2 years ago
Repo Created over 5 years ago
Repo Last Updated almost 2 years ago
Size 1.54 MB
Homepage https://pub.dartl...
Organization / Authordart-lang
Page Updated
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The dart_style package defines an automatic, opinionated formatter for Dart code. It replaces the whitespace in your program with what it deems to be the best formatting for it. Resulting code should follow the Dart style guide but, moreso, should look nice to most human readers, most of the time.

The formatter handles indentation, inline whitespace and (by far the most difficult), intelligent line wrapping. It has no problems with nested collections, function expressions, long argument lists, or otherwise tricky code.

The formatter turns code like this:

// BEFORE formatting
if (tag=='style'||tag=='script'&&(type==null||type == TYPE_JS
  tag=='link'&&(rel=='stylesheet'||rel=='import')) {}


// AFTER formatting
if (tag == 'style' ||
  tag == 'script' &&
      (type == null || type == TYPE_JS || type == TYPE_DART) ||
  tag == 'link' && (rel == 'stylesheet' || rel == 'import')) {}

The formatter will never break your codeβ€”you can safely invoke it automatically from build and presubmit scripts.

Getting dartfmt

Dartfmt is included in the Dart SDK, so you might want to add the SDK's bin directory to your system path.

If you want to make sure you are running the latest version of dartfmt, you can globally activate the package from the dart_style package on, and let pub put its executable on your path:

$ pub global activate dart_style
$ dartfmt ...

If you don't want dartfmt on your path, you can run it explicitly:

$ pub global activate dart_style --no-executables
$ pub global run dart_style:format ...

Using dartfmt

IDEs and editors that support Dart usually provide easy ways to run the formatter. For example, in WebStorm you can right-click a .dart file and then choose Reformat with Dart Style.

Here's a simple example of using dartfmt on the command line:

$ dartfmt test.dart

This command formats the test.dart file and writes the result to standard output.

Dartfmt takes a list of paths, which can point to directories or files. If the path is a directory, it processes every .dart file in that directory or any of its subdirectories. If no file or directory is specified, dartfmt reads from standard input.

By default, it formats each file and just prints the resulting code to stdout. If you pass -w, it overwrites your existing files with the formatted results.

You may pass a -l option to control the width of the page that it wraps lines to fit within, but you're strongly encouraged to keep the default line length of 80 columns.

Validating files

If you want to use the formatter in something like a presubmit script or commit hook, you can use the -n dry run option. If you specify -n, the formatter prints the paths of the files whose contents would change if the formatter were run normally. If it prints no output, then everything is already correctly formatted.

Using the dart_style API

The package also exposes a single dart_style library containing a programmatic API for formatting code. Simple usage looks like this:

import 'package:dart_style/dart_style.dart';

main() {
  var formatter = new DartFormatter();

  try {
    library an_entire_compilation_unit;

    class SomeClass {}

  } on FormatterException catch (ex) {

Other resources

  • Before sending an email, see if you are asking a frequently asked question.

  • Before filing a bug, or if you want to understand how work on the formatter is managed, see how we track issues.

dart_style open issues Ask a question     (View All Issues)
  • over 3 years move "(" to next line if callee is parenthesized cascade sequence
  • over 3 years Strange indentation after using DSL-like method call chain
  • over 3 years JSON format has apparently unnecessary "selection" field
  • over 3 years Strange formatting of list literal type
  • over 3 years dartfmt puts extra space after 'native'
  • over 3 years Non-nullable type annotation syntax
  • over 3 years Formatter should handle asserts in initializer list.
  • over 3 years Support formatting "&&=" and "||="
  • over 3 years Vertical alignment
  • almost 4 years Unfortunate formatting for a list of lists
  • almost 4 years Indentation weird on named argument function body
  • almost 4 years Pathological performance on long call chain with list literal arguments
  • about 4 years Add a line break between annotated fields
  • over 4 years allow to pass to dartfmt the body of a function without the declaration of the function
  • over 4 years dartfmt on enormous expression is slow and leaves a half-formatted long lines
  • over 4 years Flutter style mode for dartfmt
  • over 4 years Split before adjacent strings pushes string to the right
  • over 4 years Document how the formatter works
  • over 4 years Special-case decorator-style methods
  • almost 5 years Format expressions within string interpolation
  • almost 5 years Long strings for named arguments should indent 4 spaces on newlines
  • almost 5 years Output reporter should provide a list of changed files
  • almost 5 years export src/io.dart
  • almost 5 years Alignment with multiple adjacent strings
  • about 5 years Returned selection is changed
  • about 5 years Support transforming multiple selections
  • about 5 years API request for DartFormatter: String getString(AstNode)
  • about 5 years Preserve extra leading whitespace for multiline strings.
  • about 5 years Multiline strings should be weighted more towards alignment
  • about 5 years Support formatting of source selections
dart_style open pull requests (View All Pulls)
  • Always vertically align adjacent strings.
  • Improve the handling of adjacent strings.
  • Don't add extra indentation when using a decorator pattern.
  • Clean up some analyzer imports
dart_style list of languages used
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