The dartfix tool is a command-line interface for making automated updates to your Dart code. The tool isn't in the Dart SDK; instead, it's distributed in the dartfix package.


Important: Save a copy of your source code before making changes with dartfix. Unlike dartfmt, which makes only safe changes (usually to whitespace), dartfix can make changes that you might need to undo or modify.

Before you can use the dartfix tool, you need to install it, as described below. Then invoke it with the name of the directory that you want to update. When you're ready to make the suggested changes, add the --overwrite option.

$ dartfix examples/misc
... summary of recommended changes ...
$ dartfix examples/misc --overwrite


As of release 0.1.3, dartfix can make the following changes to your code:

  • Convert code to use the following features added to Dart in 2.1:

    • Find classes used as mixins, and convert them to use the mixin keyword instead of class.
    • Find double literals that end in .0, and remove the .0.
  • Move named constructor type arguments from the name to the type.
    For example, given class A<T> { A.from(Object obj) { } }, dartfix changes constructor invocations in the following way:

    Original code:
    A.from<String>(anObject) // Invokes the `A.from` named constructor.
    Code produced by dartfix:
    A<String>.from(anObject) // Same, but the type is directly after `A`.

Installing and updating dartfix

The easiest way to use dartfix is to globally install it, so that it can be in your path:

$ pub global activate dartfix

Use the same command to update dartfix. We recommend updating dartfix whenever you update your Dart SDK or when a new feature is released.


Use colors when printing messages. On by default.
-f, --force
Apply the recommended changes even if the input code has errors.
-h, --help
See a complete list of `dartfix` options.
-v, --verbose
Verbose output.
-w, --overwrite
Apply the recommended changes.

Filing issues

If you want a new fix, first look at dartfix issues and star the fixes you want. If no issue exists for the fix, create a GitHub issue.