Simple versioning with git tags

A frequently asked question on Pants Slack is how to set a version - such as for a docker image, helm chart or Python distribution - based on git state.

Pants does have various solutions for this, but they tend to be too complicated, or too limited:

• Generating version tags from Git
• Custom python_artifact() kwargs
• vcs_version target
• Using env vars to include dynamic data in tags

It turns out there is a hack that elegantly solves this problem. To make it work we need one more pants feature hidden in the docs — the .pants.bootstrap file. It makes it possible to automatically set the VERSION env var right before pants starts:

.pants.bootstrap

#!/bin/sh

VERSION="${VERSION:-$(git describe --tags --dirty --match "[0-9\.]*" || echo 0.0.1)}"
export VERSION

Now we can use the env var everywhere!

To set docker_image tag:

docker_image(
    name="image",
    image_tags=[env("VERSION")],
)

To pass docker_image build arg:

docker_image(
    name="image",
    extra_build_args=["VERSION=" + env("VERSION")],
)

To set python_distribution version:

python_distribution(
    name="mydist",
    provides=python_artifact(
        name="mydist",
        version=env("VERSION"),
    ),
)

To set helm_chart version:

helm_chart(
    version=env("VERSION"),
)