prepare_release.yml

name: Prepare release notes

on:
  workflow_dispatch:
    inputs:
      version:
        description: 'Release version notes (e.g. 3.2.0)'
        required: true
        type: string
      target_branch:
        description: 'Branch to target'
        required: false
        default: 'main'
        type: string

permissions:
  contents: write
  pull-requests: write

jobs:
  prepare:
    name: Build changelog and open PR
    runs-on: ubuntu-latest
    steps:
      - name: Validate inputs
        run: |
          if [[ ! "$VERSION" =~ ^[0-9]+\.[0-9]+\.[0-9]+([-\.][a-zA-Z0-9]+)*$ ]]; then
            echo "::error::Invalid version format: '$VERSION'"
            exit 1
          fi
          if [[ ! "$TARGET_BRANCH" =~ ^[a-zA-Z0-9._/-]+$ ]]; then
            echo "::error::Invalid branch name: '$TARGET_BRANCH'"
            exit 1
          fi
        env:
          VERSION: ${{ inputs.version }}
          TARGET_BRANCH: ${{ inputs.target_branch }}

      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
        with:
          ref: ${{ inputs.target_branch }}
          fetch-depth: 0
          persist-credentials: false

      - uses: actions/setup-python@a309ff8b426b58ec0e2a45f0f869d46889d02405 # v6.2.0
        with:
          python-version: '3.12'

      - name: Install towncrier
        run: pip install towncrier

      - name: Build changelog
        run: towncrier build --version "$VERSION" --yes
        env:
          VERSION: ${{ inputs.version }}

      - name: Create pull request
        uses: peter-evans/create-pull-request@271a8d0340265f705b14b6d32b9829c1cb33d45e # v7.0.8
        with:
          branch: release/v${{ inputs.version }}
          base: ${{ inputs.target_branch }}
          title: "Release v${{ inputs.version }}"
          body: |
            Automated release preparation for v${{ inputs.version }}.

            This PR was generated by the "Prepare release" workflow. It includes:
            - Rendered changelog via `towncrier build --version ${{ inputs.version }}`
            - Removal of consumed changelog fragments from `changes/`

            ## Checklist

            - [ ] Review the rendered changelog in `docs/release-notes.md`
            - [ ] Downstream tests pass (see [downstream workflow](https://github.com/zarr-developers/zarr-python/actions/workflows/downstream.yml))
            - [ ] Merge this PR, then [draft a GitHub Release](https://github.com/zarr-developers/zarr-python/releases/new) targeting `${{ inputs.target_branch }}` with tag `v${{ inputs.version }}`
          commit-message: "chore: build changelog for v${{ inputs.version }}"
          labels: run-downstream
          delete-branch: true