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Customizing builds

Customizing the build behavior of a package is done by creating a build.yaml file, which describes your configuration.

Defining Builders to apply to dependents (similar to transformers)

If users of your package need to apply some code generation to their package, then you can define Builders and have those applied to packages with a dependency on yours.

Exposed Builders are configured in the builders section of the build.yaml. This is a map of builder names to configuration. Each builder config may contain the following keys:

• target: The name of the target which defines contains the Builder class definition.
• import: Required. The import uri that should be used to import the library containing the Builder class. This should always be a package: uri.
• builder_factories: A List<String> which contains the names of the top-level methods in the imported library which are a function fitting the typedef Builder factoryName(List<String> args).
• build_extensions: Required. A map from input extension to the list of output extensions that may be created for that input. This must match the merged buildExtensions maps from each Builder in builder_factories.

Example builders config:

targets:
  # The target containing the builder sources.
  _my_builder: # By convention, this is private
    sources:
      - "lib/src/builder/**/*.dart"
      - "lib/builder.dart"
    dependencies:
      - "build"
      - "source_gen"
builders:
  # The actual builder config.
  my_builder:
    target: ":_my_builder"
    import: "package:my_package/builder.dart"
    builder_factories: ["myBuilder"]
    build_extensions: {".dart": [".my_package.dart"]}