README.md

About

This subaction generates a multi-dimension matrix that can be used in a GitHub matrix through the include property so you can distribute your builds across multiple runners.

---

• Usage
• Customizing
  • inputs
  • outputs

Usage

List targets

# docker-bake.hcl
group "validate" {
  targets = ["lint", "doctoc"]
}

target "lint" {
  target = "lint"
}

target "doctoc" {
  target = "doctoc"
}

jobs:
  prepare:
    runs-on: ubuntu-latest
    outputs:
      matrix: ${{ steps.generate.outputs.matrix }}
    steps:
      -
        name: Checkout
        uses: actions/checkout@v6
      -
        name: Generate matrix
        id: generate
        uses: docker/bake-action/subaction/matrix@v7
        with:
          target: validate

  validate:
    runs-on: ubuntu-latest
    needs:
      - prepare
    strategy:
      fail-fast: false
      matrix:
        include: ${{ fromJson(needs.prepare.outputs.matrix) }}
    steps:
      -
        name: Validate
        uses: docker/bake-action@v7
        with:
          targets: ${{ matrix.target }}

Platforms split

# docker-bake.hcl
target "lint" {
  dockerfile = "./hack/dockerfiles/lint.Dockerfile"
  output = ["type=cacheonly"]
  platforms = [
    "darwin/amd64",
    "darwin/arm64",
    "linux/amd64",
    "linux/arm64",
    "linux/s390x",
    "linux/ppc64le",
    "linux/riscv64",
    "windows/amd64",
    "windows/arm64"
  ]
}

jobs:
  prepare:
    runs-on: ubuntu-latest
    outputs:
      matrix: ${{ steps.generate.outputs.matrix }}
    steps:
      -
        name: Checkout
        uses: actions/checkout@v6
      -
        name: Generate matrix
        id: generate
        uses: docker/bake-action/subaction/matrix@v7
        with:
          target: lint
          fields: platforms

  lint:
    runs-on: ${{ startsWith(matrix.platforms, 'linux/arm') && 'ubuntu-24.04-arm' || 'ubuntu-latest' }}
    needs:
      - prepare
    strategy:
      fail-fast: false
      matrix:
        include: ${{ fromJson(needs.prepare.outputs.matrix) }}
    steps:
      -
        name: Lint
        uses: docker/bake-action@v7
        with:
          targets: ${{ matrix.target }}
          set: |
            *.platform=${{ matrix.platforms }}

Customizing

inputs

Name	Type	Description
workdir	String	Working directory to use (defaults to .)
files	List/CSV	List of bake definition files
target	String	The target to use within the bake file
fields	String	List of extra fields to include in the matrix

outputs

Name	Type	Description
matrix	JSON	Matrix configuration