Why is the "v" prefix ignored for alpha or beta releases?

[eliasbenb]

I'm hoping to get some insight into why my tags don't get processed as intended. My workflow is run on Git tag pushes where my tags follow semantic versioning (e.g. v0.1.0, v0.1.0-beta.1, v0.1.0-alpha.1).

      - name: Extract Docker Metadata
        id: meta
        uses: docker/metadata-action@v5
        with:
          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
          flavor: |
            latest=false
          tags: |
            type=semver,pattern=v{{version}}
            type=semver,pattern=v{{major}}.{{minor}}
            type=semver,pattern=v{{major}}
            type=raw,value=alpha,enable=${{ github.ref_type == 'tag' && contains(github.ref, 'alpha') }}
            type=raw,value=beta,enable=${{ github.ref_type == 'tag' && contains(github.ref, 'beta') }}
            type=raw,value=latest,enable=${{ github.ref_type == 'tag' && !contains(github.ref, 'alpha') && !contains(github.ref, 'beta') }}
            type=ref,event=branch

I expect my workflow to output these Docker tags for these GitHub tags:

v0.1.0 -> v0.1.0, v0.1, v0, latest, branch-name
v0.1.0-beta.1 -> v0.1.0-beta.1, beta, branch-name
v0.1.0-alpha.1 -> v0.1.0-alpha.1, alpha, branch-name

However, these are the actual outputs I'm getting:

v0.1.0 -> v0.1.0, v0.1, v0, latest, branch-name ✅
v0.1.0-beta.1 -> 0.1.0-beta.1, beta, branch-name ❌
v0.1.0-alpha.1 -> 0.1.0-alpha.1, alpha, branch-name ❌

The problem is in the "v" prefix for alpha and beta tags. For some reason, if my GitHub tag contains alpha or beta, there is no "v" prefix on the v{{version}} pattern. The prefix is correctly applied for non-alpha/beta releases.

Any thoughts? Thanks!

[polarathene]

semver will match on the tag pattern, and it strips away the v prefix which the docs kind of mention (unless you prepend the v to the pattern as you did).

For the pre-release semver tags they are intentionally not supported for major/major.minor patterns: https://github.com/docker/metadata-action#typesemver

Pre-release (rc, beta, alpha) will only extend {{version}} (or {{raw}} if specified) as tag because they are updated frequently, and contain many breaking changes that are (by the author's design) not yet fit for public consumption.

[eliasbenb]

Thanks for the reply @polarathene! This has been my solution since making the post:

- name: Set version variables
  run: |
      echo "IS_STABLE=${{ github.ref_type == 'tag' && !contains(github.ref, '-alpha.') && !contains(github.ref, '-beta.') }}" >> $GITHUB_ENV
      echo "IS_ALPHA=${{ github.ref_type == 'tag' && contains(github.ref, '-alpha.') }}" >> $GITHUB_ENV
      echo "IS_BETA=${{ github.ref_type == 'tag' && contains(github.ref, '-beta.') }}" >> $GITHUB_ENV
      echo "IS_PRERELEASE=${{ github.ref_type == 'tag' && (contains(github.ref, '-alpha.') || contains(github.ref, '-beta.')) }}" >> $GITHUB_ENV

- name: Extract Docker Metadata
  id: meta
  uses: docker/metadata-action@v5
  with:
      images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
      flavor: |
          latest=false
      tags: |
          # X.Y.Z, X.Y, X
          type=semver,pattern={{version}},enable=${{ env.IS_STABLE }}
          type=semver,pattern={{major}}.{{minor}},enable=${{ env.IS_STABLE }}
          type=semver,pattern={{major}},enable=${{ env.IS_STABLE }}
          # vX.Y.Z, vX.Y, vX
          type=semver,pattern=v{{version}},enable=${{ env.IS_STABLE }}
          type=semver,pattern=v{{major}}.{{minor}},enable=${{ env.IS_STABLE }}
          type=semver,pattern=v{{major}},enable=${{ env.IS_STABLE }}
          # X.Y.Z-alpha.W, X.Y.Z-beta.W
          type=semver,pattern={{version}},enable=${{ env.IS_PRERELEASE }}
          # vX.Y.Z-alpha.W, vX.Y.Z-beta.W
          type=semver,pattern={{raw}},enable=${{ env.IS_PRERELEASE }}
          # alpha, beta
          type=raw,value=alpha,enable=${{ env.IS_ALPHA }}
          type=raw,value=beta,enable=${{ env.IS_BETA }}
          # main, develop, experimental
          type=ref,event=branch
          # latest
          type=raw,value=latest,enable=${{ env.IS_STABLE }}

Definitely not perfect, it just passes the raw value when using a pre-release semvar pattern X.Y.Z-(alpha|beta).W, but it works for my needs.