github-release.yml

name: Create release

# Tags and releases the method library when a version bump lands on `main`.
#
# The library publishes no package: the repository is the distribution channel,
# and an address pinned to a tag (`github.com/Pipelex/methods/<name>@vX.Y.Z`)
# resolves against the annotated `vX.Y.Z` tag. That tag IS the release artifact,
# which is why this workflow creates it with `git tag -a` and then passes
# `--verify-tag` to `gh release create`: letting `gh` create the tag implicitly
# would produce a *lightweight* tag.
#
# The version is the one every `methods/*/METHODS.toml` declares, in lockstep,
# so a manifest left behind fails this workflow before anything is tagged.
#
# Pushes to `main` that carry no version bump are normal here — `main` is the
# default branch, which an address without a tag runs, and it is moved forward
# between releases — so every step is guarded on "does this tag / release
# already exist" rather than assuming the push is a release.
#
# The tag goes on the release pull request's merge commit, looked up from the
# merged pull request, never on the commit this run happens to be on. A release
# run can be cancelled while pending (a concurrency group keeps one pending run
# and cancels it when another push queues), can fail before tagging, or can be
# re-dispatched after `main` has moved; in each case the run that does the
# tagging is on a later commit, which may carry work the release does not.

on:
  push:
    branches:
      - main
  workflow_dispatch:

concurrency:
  group: ${{ github.workflow }}
  cancel-in-progress: false

jobs:
  github-release:
    name: Tag and release
    runs-on: ubuntu-latest
    permissions:
      contents: write # mandatory for pushing tags and making GitHub Releases
      pull-requests: read # to find the release pull request's merge commit

    steps:
      - name: Refuse a ref other than main
        if: github.ref != 'refs/heads/main'
        run: |
          echo "::error::This workflow releases what main carries. Dispatch it from main: a run on $GITHUB_REF could tag a release branch before its merge, and the merge would then find the tag taken."
          exit 1

      - uses: actions/checkout@v4
        with:
          fetch-depth: 0 # need the tag list to know what has already shipped

      - name: Read the version every manifest declares
        run: |
          VERSIONS=$(grep -h '^version = ' methods/*/METHODS.toml | sort -u)
          if [ "$(printf '%s\n' "$VERSIONS" | grep -c .)" -ne 1 ]; then
            echo "::error::The manifests disagree on the version, so there is no single version to release:"
            grep -H '^version = ' methods/*/METHODS.toml
            exit 1
          fi
          VERSION=$(printf '%s' "$VERSIONS" | cut -d '"' -f 2)
          if [ -z "$VERSION" ]; then
            echo "::error::Could not read a version from methods/*/METHODS.toml"
            exit 1
          fi
          echo "VERSION=$VERSION" >> "$GITHUB_ENV"
          echo "Version on main: $VERSION"

      - name: Check what already exists
        env:
          GITHUB_TOKEN: ${{ github.token }}
        run: |
          if git rev-parse -q --verify "refs/tags/v$VERSION" >/dev/null; then
            echo "TAG_EXISTS=1" >> "$GITHUB_ENV"
            echo "Tag v$VERSION already exists."
          fi
          if gh release view "v$VERSION" --repo "$GITHUB_REPOSITORY" >/dev/null 2>&1; then
            echo "RELEASE_EXISTS=1" >> "$GITHUB_ENV"
            echo "Release v$VERSION already exists."
          fi

      - name: Nothing to do
        if: env.TAG_EXISTS == '1' && env.RELEASE_EXISTS == '1'
        run: echo "v$VERSION is already tagged and released — this push carried no version bump."

      - name: Resolve the release commit
        if: env.TAG_EXISTS != '1' || env.RELEASE_EXISTS != '1'
        env:
          GITHUB_TOKEN: ${{ github.token }}
        run: |
          if [ "$TAG_EXISTS" = "1" ]; then
            TARGET=$(git rev-list -n 1 "v$VERSION")
            echo "v$VERSION is already on $TARGET; only the Release is missing."
          else
            TARGET=$(gh pr list --repo "$GITHUB_REPOSITORY" --state merged --base main --head "release/v$VERSION" \
              --json mergeCommit --jq '.[0].mergeCommit.oid // empty')
            if [ -z "$TARGET" ]; then
              echo "::error::The manifests declare $VERSION, which is not tagged, but no pull request from release/v$VERSION was merged into main — refusing to tag a commit no release pull request produced."
              exit 1
            fi
            if ! git merge-base --is-ancestor "$TARGET" HEAD; then
              echo "::error::The release pull request's merge commit $TARGET is not in main's history at $(git rev-parse HEAD) — refusing to tag."
              exit 1
            fi
            echo "The release pull request for v$VERSION merged as $TARGET."
          fi
          echo "TARGET=$TARGET" >> "$GITHUB_ENV"

      - name: Verify changelog entry exists
        if: env.TAG_EXISTS != '1' || env.RELEASE_EXISTS != '1'
        run: |
          if ! git show "$TARGET:CHANGELOG.md" | grep -q "^## \[v$VERSION\] - "; then
            echo "::error::No changelog entry for v$VERSION in CHANGELOG.md at $TARGET — refusing to tag."
            exit 1
          fi

      - name: Create and push annotated tag
        if: env.TAG_EXISTS != '1'
        run: |
          git config user.name "github-actions[bot]"
          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
          git tag -a "v$VERSION" "$TARGET" -m "Library snapshot v$VERSION"
          git push origin "v$VERSION"
          echo "Tagged $(git rev-parse --short "$TARGET") as v$VERSION"

      - name: Extract changelog notes for this version
        if: env.RELEASE_EXISTS != '1'
        run: |
          git show "$TARGET:CHANGELOG.md" > "$RUNNER_TEMP/CHANGELOG.md"
          CHANGELOG="$RUNNER_TEMP/CHANGELOG.md"
          START_LINE=$(grep -n "^## \[v$VERSION\] - " "$CHANGELOG" | cut -d: -f1)
          NEXT_VERSION_LINE=$(tail -n +$((START_LINE + 1)) "$CHANGELOG" | grep -n "^## \[v.*\] - " | head -1 | cut -d: -f1)

          if [ -z "$NEXT_VERSION_LINE" ]; then
            NOTES=$(tail -n +$((START_LINE + 1)) "$CHANGELOG")
          else
            NOTES=$(sed -n "$((START_LINE + 1)),$((START_LINE + NEXT_VERSION_LINE - 1))p" "$CHANGELOG")
          fi

          {
            echo "CHANGELOG_NOTES<<CHANGELOG_EOF"
            echo "$NOTES"
            echo "CHANGELOG_EOF"
          } >> "$GITHUB_ENV"

      - name: Create GitHub Release
        if: env.RELEASE_EXISTS != '1'
        env:
          GITHUB_TOKEN: ${{ github.token }}
        run: |
          gh release create "v$VERSION" \
            --repo "$GITHUB_REPOSITORY" \
            --title "v$VERSION" \
            --verify-tag \
            --notes "$CHANGELOG_NOTES"