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:

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.
github.ref != 'refs/heads/master' - prevents the step running on a master branch. PR comments are not possible when there's no PR!
(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

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GitHub Action

Terraform PR Commenter