How do you share Terraform plans in PRs before applying changes ?

 Sharing Terraform plans in Pull Requests (PRs) is a standard DevOps practice designed to give reviewers visibility into infrastructure changes before they are applied. You can achieve this using specialized GitOps tools, managed platforms, or custom CI/CD pipelines. [1, 2, 3, 4, 5]

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1. Dedicated GitOps Tools (Recommended)

Dedicated GitOps tools specialize in integrating Terraform operations directly into your repository's PR comment section. They handle plan visibility and state-locking natively. [1, 2, 3]

• Atlantis: An open-source, self-hosted framework that automates Terraform via PR comments. When you open a PR, Atlantis automatically runs terraform plan and prints the output as a Markdown comment. Reviewers can type atlantis apply directly in the comment section to deploy the changes. [1, 2, 3, 4, 5]
• Digger: An open-source alternative that allows you to orchestrate Terraform within your existing CI/CD provider (like GitHub Actions) rather than hosting a separate backend. It previews plans natively inside the PR and handles state-locking to prevent concurrent execution conflicts. [1, 2, 3, 4]

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2. Managed Platforms (TACOS)

Terraform Automation and Collaboration Offerings (TACOS) are enterprise-ready, managed ecosystems that provide deep integration with GitHub, GitLab, and Bitbucket. [1, 2, 3]

• Terraform Cloud / Enterprise: HashiCorp's official platform streams live plans straight into your PR interface. It shows a high-level summary (e.g., resources to add, change, or destroy) directly on the PR status check line. [1, 2, 3, 4, 5]
• Spacelift / Scalr / Env0: Alternative cloud solutions that capture terraform plan outputs. They attach an interactive, expandable summary to your PR, allowing you to click through to their dedicated dashboards for full plan exploration. [1, 2, 3, 4]

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3. Custom CI/CD Workflows (GitHub Actions & GitLab CI)

If you prefer not to use third-party tools, you can script your CI/CD platform to capture the CLI terminal output and write it to a PR comment. [1, 2]

GitHub Actions Approach

You can leverage community actions like actions/github-script or specialized marketplace extensions to inject text formatting into your workflow. A standard workflow utilizes: [1, 2]

1. terraform plan -no-color: Generates the plan without terminal ANSI color codes so it remains readable as raw text.
2. towardsthecloud/terraform-plan-pr-commenter: A popular GitHub action that formats and posts the output under an expandable Markdown <details> tag. [1, 2, 3]

yaml

# Simplified snippet for GitHub Actions
- name: Terraform Plan
  id: plan
  run: terraform plan -no-color -out=tfplan

- name: Post Plan to PR
  uses: towardsthecloud/terraform-plan-pr-commenter@v1
  with:
    github_token: ${{ secrets.GITHUB_TOKEN }}
    plan_output: ${{ steps.plan.outputs.stdout }}

GitLab CI / Merge Request Approach

In GitLab, you can utilize built-in infrastructure tracking. By configuring your pipeline to output a artifact file named blueprint.json using terraform show -json, GitLab natively parses the file and creates a structured graphical widget directly inside your Merge Request interface.

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Key Best Practices

• Use Collapsible Formatting: Raw plan files can exceed thousands of lines. Wrap the text inside HTML <details> and <summary> tags to keep your PR interface clean. [1, 2, 3]
• Mask Sensitive Data: Terraform plans sometimes display plain-text environment variables, tokens, or private certificates. Ensure your pipeline scripts strip out sensitive strings or pass files securely. [1, 2, 3, 4, 5]
• Enforce Concurrency Locks: If multiple PRs modify the same cloud environment simultaneously, their plans will overlap and become inaccurate. Configure your workflow to process plans sequentially or implement branch locks. [1, 2]

Would you like help writing a complete pipeline script for a specific CI platform, or are you interested in setting up a particular tool like Atlantis?