Monorepo

In Getting Started, there was only one root module. Now let's set up a monorepo.

foo/
  tfaction.yaml
  main.tf
  # ...
bar/
  tfaction.yaml
  main.tf
  # ...

In a monorepo, you typically want to run terraform plan and apply only for the root modules changed in a PR. This is easily achieved using GitHub Actions matrix builds and tfaction's list-targets action.

list-targets outputs a list of root modules changed in the PR. It depends on git, so the repository must be checked out before running it. A shallow clone is sufficient.

1. Add a list job

Run list-targets to get the list of target root modules and output it.

jobs:
  list:
    timeout-minutes: 10
    runs-on: ubuntu-24.04
    permissions:
      contents: read
    outputs:
      targets: ${{steps.list-targets.outputs.targets}}
    steps:
      - name: Checkout Repository
        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
        with:
          persist-credentials: false

      - name: List Targets
        uses: suzuki-shunsuke/tfaction@latest
        id: list-targets
        with:
          action: list-targets

1. Run plan using matrix builds after the list job

plan:
  name: "plan (${{matrix.target.target}})" # Different job name per root module
  timeout-minutes: 30
  runs-on: ubuntu-24.04
  needs: [list] # Run after list
  permissions:
    contents: read
  env:
    # Set environment variables per root module
    TFACTION_TARGET: "${{matrix.target.target}}"
    TFACTION_WORKING_DIR: ${{matrix.target.working_directory}}
    TFACTION_JOB_TYPE: ${{matrix.target.job_type}}
  if: "join(fromJSON(needs.list.outputs.targets), '') != ''" # Skip if no root modules changed
  strategy:
    fail-fast: false # Continue other root modules even if one fails
    matrix:
      target: ${{fromJSON(needs.list.outputs.targets)}}

This runs CI via matrix builds only for the root modules changed in the PR.

PR comments and labels include the root module path, making it easy to identify which root module each comment or label belongs to.