action.yaml

name: "What changed"
description: "Action looks at changed files since last successful workflow run and determines what changed."
inputs:
  files:
    description: "Relevant files"
    required: true
  main-branch-name:
    description: "Name of the main branch"
    required: false
    default: main
outputs:
  changed:
    description: "What changed: only-inputs, non-inputs, both"
    value: ${{ steps.changed-files.outputs.changed }}
runs:
  using: "composite"
  steps:
    - uses: "actions/checkout@v4"
      with:
        fetch-depth: 0
    - name: Find start and end SHAs
      uses: nrwl/nx-set-shas@v4
      id: last-successful-commit-push
      with:
        main-branch-name: ${{ inputs.main-branch-name }}
    - name: Determine what changed
      id: changed-files
      shell: python
      env:
        INPUT_BASE: ${{ steps.last-successful-commit-push.outputs.base }}
        INPUT_HEAD: ${{ steps.last-successful-commit-push.outputs.head }}
        INPUT_FILEPATHS: ${{ inputs.files }}
      run: |
        # Generated code below, DO NOT EDIT THIS LINE OR BELOW
        import glob
        import logging
        import os
        import subprocess
        from dataclasses import dataclass
        from itertools import chain

        LOG = logging.getLogger(__name__)


        @dataclass
        class Options:
            base: str
            head: str
            filepaths: str


        def setup_logging():
            logging.basicConfig(level=logging.DEBUG, format="::%(levelname)s::%(message)s")
            # GitHub wants lowercase levelnames for workflow commands mapping
            for level in logging.getLevelNamesMapping().values():
                logging.addLevelName(level, logging.getLevelName(level).lower())


        def main(options):
            setup_logging()
            cmd = ["git", "diff", "--name-only", options.base, options.head]
            changed_files = set(subprocess.run(cmd, capture_output=True, text=True).stdout.splitlines())
            LOG.debug("Changed files: %r", changed_files)
            input_files = set(chain(*(glob.glob(f) for f in options.filepaths.split(","))))
            LOG.debug("Input files: %r", input_files)

            if changed_files.issubset(input_files):
                LOG.info("Only inputs have been changed")
                output = "only-inputs"
            elif input_files.isdisjoint(changed_files):
                LOG.info("No inputs have been changed")
                output = "non-inputs"
            else:
                LOG.info("Both inputs and other files have been changed")
                output = "both"

            output_file = os.getenv("GITHUB_OUTPUT")
            if output_file:
                with open(output_file, "a") as f:
                    f.write(f"changed={output}\n")
            else:
                LOG.info("No GITHUB_OUTPUT environment variable found, printing to stdout")
                LOG.info(f"changed={output}")


        if __name__ == '__main__':
            options = Options(
                os.getenv("INPUT_BASE"),
                os.getenv("INPUT_HEAD"),
                os.getenv("INPUT_FILEPATHS"),
            )
            main(options)