Terraform PR Commenter

Adds opinionated comments to PR's based on Terraform fmt, init, plan and validate outputs.

Summary

This Docker-based GitHub Action is designed to work in tandem with hashicorp/setup-terraform with the wrapper enabled, taking the output from a fmt, init, plan or validate, formatting it and adding it to a pull request. Any previous comments from this Action are removed to keep the PR timeline clean.

The terraform_wrapper needs to be set to true (which is already the default) for the hashicorp/setup-terraform step as it enables the capturing of stdout, stderr and the exitcode.

Support (for now) is limited to Linux as Docker-based GitHub Actions can only be used on Linux runners.

Usage

This action can only be run after a Terraform fmt, init, plan or validate has completed, and the output has been captured. Terraform rarely writes to stdout and stderr in the same action, so we concatenate the commenter_input:

- uses: robburger/terraform-pr-commenter@v1
  env:
    GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
  with:
    commenter_type: fmt/init/plan/validate # Choose one
    commenter_input: ${{ format('{0}{1}', steps.step_id.outputs.stdout, steps.step_id.outputs.stderr) }}
    commenter_exitcode: ${{ steps.step_id.outputs.exitcode }}

Inputs

Name	Requirement	Description
commenter_type	required	The type of comment. Options: [fmt, init, plan, validate]
commenter_input	required	The comment to post from a previous step output.
commenter_exitcode	required	The exit code from a previous step output.

Environment Variables

Name	Requirement	Description
GITHUB_TOKEN	required	Used to execute API calls. The ${{ secrets.GITHUB_TOKEN }} already has permissions, but if you're using your own token, ensure it has the repo scope.
TF_WORKSPACE	optional	Default: default. This is used to separate multiple comments on a pull request in a matrix run.
EXPAND_SUMMARY_DETAILS	optional	Default: true. This controls whether the comment output is collapsed or not.
HIGHLIGHT_CHANGES	optional	Default: true. This switches ~ to ! in plan diffs to highlight Terraform changes in orange. Set to false to disable.

All of these environment variables can be set at job or step level. For example, you could collapse all outputs but expand on a plan:

jobs:
  terraform:
    name: 'Terraform'
    runs-on: ubuntu-latest
    env:
      EXPAND_SUMMARY_DETAILS: 'false' # All steps will have this environment variable
    steps:
      - name: Checkout
        uses: actions/checkout@v2
...
      - name: Post Plan
        uses: robburger/terraform-pr-commenter@v1
        env:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
          EXPAND_SUMMARY_DETAILS: 'true' # Override global environment variable; expand details just for this step
        with:
          commenter_type: plan
          commenter_input: ${{ format('{0}{1}', steps.plan.outputs.stdout, steps.plan.outputs.stderr) }}
          commenter_exitcode: ${{ steps.plan.outputs.exitcode }}
...

Examples

Single workspace build, full example:

name: 'Terraform'

on:
  pull_request:
  push:
    branches:
      - master

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

      - name: Setup Terraform
        uses: hashicorp/setup-terraform@v1
        with:
          cli_config_credentials_token: ${{ secrets.TF_API_TOKEN }}
          terraform_version: 0.15.0

      - name: Terraform Format
        id: fmt
        run: terraform fmt -check -recursive
        continue-on-error: true

      - name: Post Format
        if: always() && github.ref != 'refs/heads/master' && (steps.fmt.outcome == 'success' || steps.fmt.outcome == 'failure')
        uses: robburger/terraform-pr-commenter@v1
        with:
          commenter_type: fmt
          commenter_input: ${{ format('{0}{1}', steps.fmt.outputs.stdout, steps.fmt.outputs.stderr) }}
          commenter_exitcode: ${{ steps.fmt.outputs.exitcode }}

      - name: Terraform Init
        id: init
        run: terraform init

      - name: Post Init
        if: always() && github.ref != 'refs/heads/master' && (steps.init.outcome == 'success' || steps.init.outcome == 'failure')
        uses: robburger/terraform-pr-commenter@v1
        with:
          commenter_type: init
          commenter_input: ${{ format('{0}{1}', steps.init.outputs.stdout, steps.init.outputs.stderr) }}
          commenter_exitcode: ${{ steps.init.outputs.exitcode }}

      - name: Terraform Validate
        id: validate
        run: terraform validate

      - name: Post Validate
        if: always() && github.ref != 'refs/heads/master' && (steps.validate.outcome == 'success' || steps.validate.outcome == 'failure')
        uses: robburger/terraform-pr-commenter@v1
        with:
          commenter_type: validate
          commenter_input: ${{ format('{0}{1}', steps.validate.outputs.stdout, steps.validate.outputs.stderr) }}
          commenter_exitcode: ${{ steps.validate.outputs.exitcode }}

      - name: Terraform Plan
        id: plan
        run: terraform plan -out workspace.plan

      - name: Post Plan
        if: always() && github.ref != 'refs/heads/master' && (steps.plan.outcome == 'success' || steps.plan.outcome == 'failure')
        uses: robburger/terraform-pr-commenter@v1
        with:
          commenter_type: plan
          commenter_input: ${{ format('{0}{1}', steps.plan.outputs.stdout, steps.plan.outputs.stderr) }}
          commenter_exitcode: ${{ steps.plan.outputs.exitcode }}

      - name: Terraform Apply
        id: apply
        if: github.ref == 'refs/heads/master' && github.event_name == 'push'
        run: terraform apply workspace.plan

Multi-workspace matrix/parallel build:

...
jobs:
  terraform:
    name: 'Terraform'
    runs-on: ubuntu-latest
    strategy:
      matrix:
        workspace: [audit, staging]
    env:
      GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
      TF_IN_AUTOMATION: true
      TF_WORKSPACE: ${{ matrix['workspace'] }}
    steps:
      - name: Checkout
        uses: actions/checkout@v2

      - name: Setup Terraform
        uses: hashicorp/setup-terraform@v1
        with:
          cli_config_credentials_token: ${{ secrets.TF_API_TOKEN }}
          terraform_version: 0.15.0

      - name: Terraform Init - ${{ matrix['workspace'] }}
        id: init
        run: terraform init

      - name: Post Init - ${{ matrix['workspace'] }}
        if: always() && github.ref != 'refs/heads/master' && (steps.init.outcome == 'success' || steps.init.outcome == 'failure')
        uses: robburger/terraform-pr-commenter@v1
          with:
            commenter_type: init
            commenter_input: ${{ format('{0}{1}', steps.init.outputs.stdout, steps.init.outputs.stderr) }}
            commenter_exitcode: ${{ steps.init.outputs.exitcode }}

      - name: Terraform Plan - ${{ matrix['workspace'] }}
        id: plan
        run: terraform plan -out ${{ matrix['workspace'] }}.plan

      - name: Post Plan - ${{ matrix['workspace'] }}
        if: always() && github.ref != 'refs/heads/master' && (steps.plan.outcome == 'success' || steps.plan.outcome == 'failure')
        uses: robburger/terraform-pr-commenter@v1
        with:
          commenter_type: plan
          commenter_input: ${{ format('{0}{1}', steps.plan.outputs.stdout, steps.plan.outputs.stderr) }}
          commenter_exitcode: ${{ steps.plan.outputs.exitcode }}
...

"What's the crazy-looking if: doing there?" Good question! It's broken into 3 logic groups separated by &&, so all need to return true for the step to run:

1. always() - ensures that the step is run regardless of the outcome in any previous steps. i.e. We don't want the build to quit after the previous step before we can write a PR comment with the failure reason.
2. github.ref != 'refs/heads/master' - prevents the step running on a master branch. PR comments are not possible when there's no PR!
3. (steps.step_id.outcome == 'success' || steps.step_id.outcome == 'failure') - ensures that this step only runs when step_id has either a success or failed outcome.

In English: "Always run this step, but only on a pull request and only when the previous step succeeds or fails...and then stop the build."

Screenshots

fmt

init

plan

validate

Troubleshooting & Contributing

Feel free to head over to the Issues tab to see if the issue you're having has already been reported. If not, open a new one and be sure to include as much relevant information as possible, including code-samples, and a description of what you expect to be happening.

License

MIT