Paketo Buildpack for Yarn

The Yarn CNB provides the Yarn Package manager. The buildpack installs yarn onto the $PATH which makes it available for subsequent buildpacks and/or in the final running container. An example of buildpack that might use yarn is the Yarn Install CNB

Integration

The Yarn CNB provides yarn as dependency. Downstream buildpacks, like Yarn Install CNB can require the yarn dependency by generating a Build Plan TOML file that looks like the following:

[[requires]]

  # The name of the Yarn dependency is "yarn". This value is considered
  # part of the public API for the buildpack and will not change without a plan
  # for deprecation.
  name = "yarn"

  # The Yarn buildpack supports some non-required metadata options.
  [requires.metadata]

    # The version of the Yarn dependency is not required. In the case it
    # is not specified, the buildpack will provide the default version, which can
    # be seen in the buildpack.toml file.
    # If you wish to request a specific version, the buildpack supports
    # specifying a semver constraint in the form of "1.*", "1.22.*", or even
    # "1.22.4".
    version = "1.22.4"

    # Setting the build flag to true will ensure that the yarn
    # depdendency is available on the $PATH for subsequent buildpacks during
    # their build phase. If you are writing a buildpack that needs to run yarn
    # during its build process, this flag should be set to true.
    build = true

    # Setting the launch flag to true will ensure that the yarn
    # dependency is available on the $PATH for the running application. If you are
    # writing an application that needs to run yarn at runtime, this flag should
    # be set to true.
    launch = true

Usage

To package this buildpack for consumption:

$ ./scripts/package.sh --version <version-number>

This will create a buildpackage.cnb file under the build directory which you can use to build your app as follows:

pack build <app-name> \
  --path <path-to-app> \
  --buildpack <path/to/node-engine.cnb> \
  --buildpack build/buildpackage.cnb \
  --buildpack <path/to/cnb-that-requires-node-and-yarn>

Though the API of this buildpack does not require node, yarn is unusable without node.

Run Tests

To run all unit tests, run:

./scripts/unit.sh

To run all integration tests, run:

/scripts/integration.sh