Automate GitHub PR linting with Google Gemini AI and auto-fix PRs

LintGuardian: Automated PR Linting with n8n & AI

What It Does

LintGuardian is an n8n workflow template that automates code quality enforcement for GitHub repositories. When a pull request is created, the workflow automatically analyzes the changed files, identifies linting issues, fixes them, and submits a new PR with corrections. This eliminates manual code style reviews, reduces back-and-forth comments, and lets your team focus on functionality rather than formatting.

How It Works

The workflow is triggered by a GitHub webhook when a PR is created. It fetches all changed files from the PR using the GitHub API, processes them through an AI-powered linting service (Google Gemini), and automatically generates fixes. The AI agent then creates a new branch with the corrected files and submits a "linting fixes" PR against the original branch. Developers can review and merge these fixes with a single click, keeping code consistently formatted with minimal effort.

Prerequisites

To use this template, you'll need:

1. n8n instance: Either self-hosted or using n8n.cloud
2. GitHub repository: Where you want to enforce linting standards
3. GitHub Personal Access Token: With permissions for repo access (repo, workflow, admin:repo_hook)
4. Google AI API Key: For the Gemini language model that powers the linting analysis
5. GitHub webhook: Configured to send PR creation events to your n8n instance

Setup Instructions

1. Import the template into your n8n instance
2. Configure credentials:
   • Add your GitHub Personal Access Token under Credentials → GitHub API
   • Add your Google AI API key under Credentials → Google Gemini API
3. Update repository information:
   • Locate the "Set Common Fields" code node at the beginning of the workflow
   • Change the gitHubRepoName and gitHubOrgName values to match your repository

   const commonFields = {
     'gitHubRepoName': 'your-repo-name',
     'gitHubOrgName': 'your-org-name'
   }
   

4. Configure the webhook: Create a file named .github/workflows/lint-guardian.yml in your repository replacing the Trigger n8n Workflow step with your webhook:

   name: Lint Guardian
   
   on:
     pull_request:
       types: [opened, synchronize]
   
   jobs:
     trigger-linting:
       runs-on: ubuntu-latest
       steps:
         - name: Trigger n8n Workflow
           uses: fjogeleit/http-request-action@v1
           with:
             url: 'https://your-n8n-instance.com/webhook/1da5a6e1-9453-4a65-bbac-a1fed633f6ad'
             method: 'POST'
             contentType: 'application/json'
             data: |
               {
                 "pull_request_number": ${{ github.event.pull_request.number }},
                 "repository": "${{ github.repository }}",
                 "branch": "${{ github.event.pull_request.head.ref }}",
                 "base_branch": "${{ github.event.pull_request.base.ref }}"
               }
             preventFailureOnNoResponse: true
   

5. Customize linting rules (optional):
   • Modify the AI Agent's system message to specify your team's linting preferences
   • Adjust file handling if you have specific file types to focus on or ignore

Security Considerations

When creating your GitHub Personal Access Token, remember to:

• Choose the minimal permissions needed (repo, workflow, admin:repo_hook)
• Set an appropriate expiration date
• Treat your token like a password and store it securely
• Consider using GitHub's fine-grained personal access tokens for more limited scope

As GitHub documentation notes: "Personal access tokens are like passwords, and they share the same inherent security risks."

Extending the Template

You can enhance this workflow by:

• Adding Slack notifications when linting fixes are submitted
• Creating custom linting rules specific to your team's needs
• Expanding it to handle different types of code quality checks
• Adding approval steps for more controlled environments

This template provides an excellent starting point that you can customize to fit your team's exact workflow and code style requirements.