Poetry Install Cloud Native Buildpack

gcr.io/paketo-buildpacks/poetry-install

The Paketo Buildpack for Poetry Install is a Cloud Native Buildpack that installs packages using Poetry and makes the installed packages available to the application.

The buildpack is published for consumption at gcr.io/paketo-buildpacks/poetry-install and paketobuildpacks/poetry-install.

Behavior

This buildpack participates if pyproject.toml exists at the root the app.

The buildpack will do the following:

• At build time:
  • Creates a virtual environment, installs the application packages to it, and makes this virtual environment available to the app via a layer called poetry-venv.
  • Configures poetry to locate this virtual environment via the environment variable POETRY_VIRTUAL_ENVS_PATH.
  • Prepends the layer poetry-venv onto PYTHONPATH.
  • Prepends the bin directory of the poetry-venv layer to the PATH environment variable.
• At run time:
  • Does nothing

Integration

The Poetry Install CNB provides poetry-venv as a dependency. Downstream buildpacks can require the poetry-venv dependency by generating a Build Plan TOML file that looks like the following:

[[requires]]

  # The name of the dependency provided by the Poetry Install Buildpack is
  # "poetry-venv". This value is considered part of the public API for the
  # buildpack and will not change without a plan for deprecation.
  name = "poetry-venv"

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

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

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

Usage

To package this buildpack for consumption:

$ ./scripts/package.sh --version x.x.x

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> -p <path-to-app> -b <cpython buildpack> -b <poetry buildpack> -b build/buildpackage.cnb -b <other-buildpacks..>.

To run the unit and integration tests for this buildpack:

$ ./scripts/unit.sh && ./scripts/integration.sh

Known issues and limitations

• This buildpack will not work in an offline/air-gapped environment: vendoring of dependencies is not supported. This is a limitation of poetry - which itself does not support vendoring dependencies.