The build_runner package provides general-purpose commands for generating files, including testing the generated files or serving both source and generated files. This page explains how to use
build_runner. To learn how to use build_runner with a specific package, see the documentation for that package.
The build_runner commands work with builders—packages that use the Dart build system to generate output files from input files. For example, the json_serializable and built_value_generator packages define builders that generate Dart code.
Although the Dart build system is a good alternative to reflection (which has performance issues) and macros (which Dart's compilers don't support), it can do more than just read and write Dart code. For example, the sass_builder package implements a builder that generates
.css files from
Setting up build_runner#
To use build_runner, add a dev dependency on build_runner to your app's pubspec:
Depending on build_test is optional; do it if you'll be testing your code.
As usual after
pubspec.yaml changes, run
dart pub get or
dart pub upgrade:
$ dart pub get
Using built-in commands#
The following is an example of using the build_runner build command:
$ # From a directory that contains a pubspec.yaml file:
$ dart run build_runner build
The build_runner package includes the following commands:
- Performs a one-time build.
- Runs a development server. Instead of directly using this command, you can use
webdev serve, which has convenient default behavior.
- Runs tests.
- Launches a build server that watches for edits to input files. Responds to changes by performing incremental rebuilds.
If you're working on web-specific code, see the webdev page.
For details on using build_runner, see the following: