Terraform Change Pull Request Commenter Action

This GitHub Action reads changes from your Terraform plan JSON output, summarizes the changes, and posts them in a single GitHub Pull Request comment.

We recommend using this in your Infrastructure as Code delivery workflow to make any change visible and acclerate the PR review process.

Why is this GitHub Action different than the other Terraform Plan commenters?

Implementing this Action is super simple and the comments are consise and easy to read. Other implementations may be heavily opinionated or require adding multiple jobs to your workflow.

Features

• Display changes in a Terraform plan without posting larger sections of the plan change log. This approach will, in most cases, avoid the situation where plan contents are too large for a single PR comment.
• Collapsed as a summary by default, when expanded, the comment is broken up into sections for deletion, creation, and resource changes. The changes are also color-coded to help draw attention to each proposed modification.
• This JavaScript GitHub Action runs directly on a host runner and executes faster than a Docker container Action.

Example Comment

Inputs

expand-comment

Optional Boolean defaults to false

• Will expand the changes in comments by default rather than having them collapsed beneath the summary

json-file

Optional Defaults to tfplan.json

• The location of the JSON file created by running terraform show -no-color -json tfplan.plan > tfplan.json (Or whatever you choose to name your plan or json outputs)

• Multiple files can be provided using a text block.

Example usage

Single plan file:

uses: liatrio/terraform-change-pr-commenter@v1.4.0
with:
  json-file: my-tfplan.json
  expand-comment: 'true' 

Multiple plan files:

uses: liatrio/terraform-change-pr-commenter@v1.4.0
with:
  json-file: |
    core-infra-tfplan.json
    shared-infra-tfplan.json

Include plan output to the Actions workflow job summary:

uses: liatrio/terraform-change-pr-commenter@v1.4.0
with:
  json-file: my-tfplan.json
  expand-comment: 'true'
  include-plan-job-summary: 'true'

Note:

• When include-plan-job-summary = true, if the action is executed in non-Pull Request workflows, the plan output will also be posted to the job summary of that run. If you do not wish to have this behavior, apply conditional logic to your workflow file.

Example Job Summary Output

Terraform Configuration / Known Issues

Known issue when including the Terraform Wrapper script

• Execution may error with Error: Unexpected token c in JSON at position 1
  • Cause: Terraform wrapper enabled (default behavior) causes invalid JSON in Terraform output.
  • Fix: Exclude the Terraform Wrapper when setting up Terraform (GitHub Actions example)

    - name: Setup Terraform
      uses: hashicorp/setup-terraform@v2
      with:
        terraform_wrapper: false

Contributing or Submitting Issues

Contributions are welcome!

If you'd like to suggest changes, feel free to submit a Pull Request or open an issue.

Otherwise if things aren't working as expected, please open a new issue. Pleae include code references, a description of the issue, and expected behavior.

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