PR-03 at Hacktoberfest: Implementing a Credit Card Validator for Terraform Provider

My First Open Source Contribution: Implementing a Credit Card Validator for Terraform Provider

How It Started

I recently found an interesting GitHub project — terraform-provider-validatefx, a Terraform provider that adds validation functions for HCL. One open issue (#37) asked for a credit card validator. It looked like a great opportunity to learn and make my first open-source pull request.

Understanding the Project

Before coding, I learned how a Terraform Provider works:

• Terraform is an “Infrastructure as Code” tool by HashiCorp.
• Providers are plugins that extend Terraform with new resources or functions.
• ValidateFX provides validation helpers (like validatefx_email() or validatefx_uuid()).

Implementing the Validator

Each validator follows the same pattern:

1. Implement the frameworkvalidator.String interface.
2. Add descriptions.
3. Write ValidateString() for actual checks.

I implemented the Luhn algorithm to validate card numbers:

• Remove spaces and hyphens.
• Ensure 13–19 digits and numeric only.
• Reject all zeros.
• Perform Luhn checksum validation.

Writing Tests

I added comprehensive tests for:

✅ Valid cards (Visa, MasterCard, Amex)

✅ Formatted inputs (spaces, hyphens)

❌ Invalid cases (checksum, wrong length, letters, all zeros)

and edge cases (empty, null, unknown).

Technical Challenges

• Line endings: Git detected false changes → fixed with core.autocrlf.
• Integration tests: some Docker tests failed due to existing repo issues.
• Unimplemented functions: the repo references validatefx_email() etc., so I focused only on the validator logic.

What I Learned

Technical:

• Terraform Plugin Framework basics.
• Luhn algorithm logic.
• Cross-platform setup and test-driven development.

Collaboration:

• Reading existing patterns before adding code.
• Scoping work to one issue.
• Communicating clearly in PRs.

Result

My PR included:

• 1 new validator file
• 1 complete test file
• Full Luhn-based validation logic

Takeaways

This first contribution taught me both coding and collaboration.

If you want to start with open source:

• Pick a small, well-defined issue.
• Understand the project first.
• Write clear tests.
• Be patient — every issue is a learning opportunity.