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A tool to migrate API usage to Dart 2.

What does it do?

dart2_fix is a command line utility that can automatically migrate some Dart 1 API usages in your source code to Dart 2 ones. Currently, it focuses on updating deprecated constant names; for example:

  • update dart:convert's UTF8 to utf8
  • update dart:core's Duration.ZERO to
  • update dart:math's PI to pi

For more information about preparing your code for Dart 2, please see the Dart 2 migration guide.

How do I use it?

To install, run pub global activate dart2_fix. Then, from your project directory, run:

pub global run dart2_fix

When run without any arguments, it will check your project, but will not make changes; it'll indicate what would be changed if asked to make modifications. For example:

  line 56 • Duration.ZERO =>
  line 60 • Duration.ZERO =>
  line 86 • Duration.ZERO =>

  line 169 • JSON => json
  line 173 • JSON => json

Found 5 fixes in 2.3s.

To apply these fixes, run again using the --apply argument.

To actually modify your project source code, run with the --apply argument (pub global run dart2_fix --apply):

Updating test...

  3 fixes applied for Duration.ZERO =>

  2 fixes applied for JSON => json

Applied 5 fixes in 1.9s.

What about Flutter code?

To run this tool on Flutter code, use:

flutter packages pub global activate dart2_fix

then - to check your code - run:

flutter packages pub global run dart2_fix

and to apply fixes, run:

flutter packages pub global run dart2_fix --apply

Will this make all of my code Dart 2 compliant?

No. Currently this only fixes the renaming of various deprecated constant names. Some of the less uniform constant renamings are not handled by this tool. For example Endianness.BIG_ENDIAN has been renamed to Endian.big but this will not be caught. After running this tool, remaining issues can be found by running the dart analyzer (or flutter analyze) and fixing any deprecation warnings.

I'm getting new static (or runtime errors) after running dart2_fix, what went wrong?

This tool can't catch conflicts between the new constant names and any fields or local variables that you might have in scope. If you get new analysis warnings or runtime failures after running this tool, check to see whether one of the changes made has caused a naming conflict with something else in scope. The most common cause of this is having a local variable named json in a scope where JSON.decode gets renamed to json.decode. To help with fixing these kinds of conflicts, the following top level members have been added to dart:convert: jsonDecode, jsonEncode, base64Decode, base64Encode, and base64UrlEncode. These top level members are equivalent to json.decode, json.decode, etc, and can be used to avoid naming conflicts where required.

Features and bugs

Please file feature requests and bugs at the issue tracker.