This is one of a suite of terraform related actions - find them at dflook/terraform-github-actions.

This actions generates a terraform plan. If the triggering event relates to a PR it will add a comment on the PR containing the generated plan.

The GITHUB_TOKEN environment variable is must be set for the PR comment to be added. The action can be run on other events, which prints the plan to the workflow log.

The dflook/terraform-apply action can be used to apply the generated plan.

• path

  Path to the terraform configuration

  • Type: string
  • Required

• workspace

  Terraform workspace to run the plan for

  • Type: string
  • Optional
  • Default: default

• label

  An friendly name for the environment the terraform configuration is for. This will be used in the PR comment for easy identification.

  It must be the same as the label used in the corresponding terraform-apply command.

  • Type: string
  • Optional

• var

  Comma separated list of terraform vars to set

  • Type: string
  • Optional

• var_file

  Comma separated list of tfvars files to use. Paths should be relative to the GitHub Actions workspace

  • Type: string
  • Optional

• backend_config

  Comma separated list of terraform backend config values.

  • Type: string
  • Optional

• backend_config_file

  Comma separated list of terraform backend config files to use. Paths should be relative to the GitHub Actions workspace

  • Type: string
  • Optional

• parallelism

  Limit the number of concurrent operations

  • Type: number
  • Optional
  • Default: 10

• add_github_comment

  The default is true, which adds a comment to the PR with the generated plan. Set to false to disable the comment - the plan will still appear in the workflow log.

  • Type: bool
  • Optional
  • Default: true

• GITHUB_TOKEN

  The GitHub authorization token to use to create comments on a PR. The token provided by GitHub Actions can be used - it can be passed by using the ${{ secrets.GITHUB_TOKEN }} expression, e.g.

  env:
    GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

• changes

  Set to 'true' if the plan would apply any changes, 'false' if it wouldn't.

  Note that with terraform <0.13 an apply may still be needed to update any outputs, even if no resources would change. With terraform >=0.13 this is correctly set to 'true' whenever an apply needs to be run.

This example workflow runs on every push to an open pull request, and create or updates a comment with the terraform plan

name: PR Plan

on: [pull_request]

jobs:
  plan:
    runs-on: ubuntu-latest
    name: Create terraform plan
    env:
      GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}            
    steps:
      - name: Checkout
        uses: actions/checkout@v2

      - name: terraform plan
        uses: dflook/terraform-plan@v1
        with:
          path: my-terraform-config

This workflow generates a plan on demand, triggered by someone commenting terraform plan on the PR. The action will create or update a comment on the PR with the generated plan.

name: Terraform Plan

on: [issue_comment]

jobs:
  plan:
    if: github.event.issue.pull_request && contains(github.event.comment.body, 'terraform plan')
    runs-on: ubuntu-latest
    name: Create terraform plan
    env:
      GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
    steps:
      - name: Checkout
        uses: actions/checkout@v2
        with:
          ref: refs/pull/${{ github.event.issue.number }}/merge

      - name: terraform plan
        uses: dflook/terraform-plan@v1
        with:
          path: my-terraform-config