action.yml

name: "Pre-commit"
description: |
  Runs the consuming repo's .pre-commit-config.yaml hooks in CI — the non-bypassable
  counterpart to a developer's local pre-commit hook. Language-agnostic: all hook
  configuration lives in the consuming repo's config.

  On a pull_request it runs hooks only against the changed files
  (--from-ref/--to-ref); otherwise it runs against all files. Fails on any hook
  that exits non-zero.

  Required permissions on calling job: contents: read
inputs:
  version:
    description: "pre-commit version to install (no leading 'v')."
    default: "4.6.0"
  config-path:
    description: "Path to the pre-commit config in the consuming repo."
    default: ".pre-commit-config.yaml"
  from-ref:
    description: "Lower bound of the diff to scan. Defaults to the PR base SHA."
    default: ${{ github.event.pull_request.base.sha || '' }}
  to-ref:
    description: "Upper bound of the diff to scan. Defaults to the PR head SHA."
    default: ${{ github.event.pull_request.head.sha || '' }}
runs:
  using: "composite"
  steps:
    - name: Run pre-commit
      shell: bash
      env:
        PRE_COMMIT_VERSION: ${{ inputs.version }}
        CONFIG_PATH: ${{ inputs.config-path }}
        FROM_REF: ${{ inputs.from-ref }}
        TO_REF: ${{ inputs.to-ref }}
      run: |
        set -euo pipefail
        if [ ! -f "${CONFIG_PATH}" ]; then
          echo "::error::pre-commit config not found at ${CONFIG_PATH}"
          exit 1
        fi
        ARGS=(run --config "${CONFIG_PATH}" --show-diff-on-failure --color always)
        if [ -n "${FROM_REF}" ] && [ -n "${TO_REF}" ]; then
          echo "Running pre-commit on changed files ${FROM_REF}..${TO_REF}"
          ARGS+=(--from-ref "${FROM_REF}" --to-ref "${TO_REF}")
        else
          echo "Running pre-commit on all files"
          ARGS+=(--all-files)
        fi
        # pipx is preinstalled on GitHub-hosted runners; `pipx run` executes a
        # pinned pre-commit in an ephemeral env — no GITHUB_PATH write and no
        # PEP-668 "externally-managed" pip error on the system Python.
        pipx run --spec "pre-commit==${PRE_COMMIT_VERSION}" pre-commit "${ARGS[@]}"