Monorepo

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

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

In a monorepo, you likely want to run terraform plan and apply only for the root modules changed in a PR. You can easily achieve this using GitHub Actions matrix builds and tfaction's list-targets action. list-targets outputs a list of root modules changed in the PR. Since list-targets depends on git, you need to checkout the repository before running it. However, 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

2. Run plan with matrix builds after the list job

  plan:
    name: "plan (${{matrix.target.target}})" # Use a different job name for each root module
    timeout-minutes: 60
    runs-on: ubuntu-24.04
    needs: [list] # Run after list
    permissions:
      contents: read
    env:
      # Set environment variables for each root module
      TFACTION_TARGET: "${{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 were changed
    strategy:
      fail-fast: false # Continue running other root modules even if one fails
      matrix:
        target: ${{fromJSON(needs.list.outputs.targets)}}

This way, CI runs only for the root modules changed in the PR using matrix builds.

PR comments and labels also include the root module path, making it easy to distinguish which root module they relate to.