n8n Automated AI Code Review: Lint + Gemini Scoring + Google Sheets Logging + Slack Alerts

Google Sheets code input → n8n triggers dual-layer lint and AI review → outputs red-marked corrections with scores to spreadsheet and notifies Slack

Who

Software engineers, QA teams, and tech leads

You get

Automatically trigger code reviews in Google Sheets, get lint results, AI red-marked correction suggestions, a 0-10 composite score, and push summaries to Slack

You need

n8n · Google Sheets · Slack

Steps

1. Connect credentials and replace placeholders

   In n8n, connect Google Sheets OAuth2 and Slack OAuth2 credentials. After importing the template, replace all placeholders with actual values: - `<YOUR_SPREADSHEET_ID>` → your Google Sheet document ID - `<YOUR_SHEET_GID_OR_NAME>` → input code worksheet name (e.g., 「対象コード」) and review results worksheet name (e.g., 「レビュー結果」) - `<YOUR_SLACK_CHANNEL_ID>` → your Slack channel ID Confirm the Google Sheets nodes have credentials selected and the Slack node has authentication set to oAuth2.

2. Configure AI Agent and optional conventions sheet

   Confirm the AI Agent node is connected to Google Gemini Chat Model as its language model. Check whether the 'Get row(s) in sheet in Google Sheets' tool node points to your coding conventions worksheet (コード規約); this tool is invoked by the AI Agent to retrieve project guidelines. Adjust documentId and sheetName if needed.

3. Adjust review prompt and lint rules (optional)

   Modify the AI Agent node prompt or Lint Check function node rules based on project needs. The source prompt is mixed Japanese-English and requires HTML red-tag formatting. When extending lint rules, maintain compatible output format (lintErrors array with type and msg fields, lintScore 0-10).

   Execution prompt · Source text。AI Agent node text parameter (promptType=define)

   Copy prompt

   =Lint summary (consider in review):
   {{ JSON.stringify($('Lint Check').first().json.lintErrors) }}
   
   Lint score: {{ $('Lint Check').first().json.lintScore }} / 10
   
   =あなたはコードレビューの専門家です。以下のコードをレビューし、修正が必要な箇所を赤字で示してください。元のコードに対して、修正案を赤字（HTMLの<span style="color:red">タグ）で追記した形式で出力してください。
   
   {{ $json.reviewPrompt }}
   
   コード:
   {{ $('コード入力シート監視').item.json.code }}
   
   【Review Rules】
   - Classify issues as Critical / Major / Minor
   - Use <span style="color:red">red</span> for critical fixes; <span style="color:orange">orange</span> for minor suggestions
   - Append JSON at end: {"overall_score": <0-10 number>}

4. Trigger workflow by entering code in the sheet

   Add a new row in the 「対象コード」 worksheet, ensuring it includes a code field (column name must match trigger configuration). The n8n Google Sheets Trigger node (コード入力シート監視) polls every minute for new or edited rows and automatically starts the workflow.

5. Observe dual-layer review execution

   The workflow executes in this order: 1. Lint Check function node runs static analysis, outputting lintErrors (Critical/Major/Minor classification) and lintScore (0-10). 2. AI Agent node sends code, lint summary, and conventions sheet content to Gemini, requesting red/orange HTML-marked corrections and appending {"overall_score": N} JSON at the end. 3. Format Review Output function node parses AI output, extracts overall_score, and averages it with lintScore to produce overallScore. 4. Aggregate Review Stats function node counts severity levels and generates summaryText.

6. Review outputs: spreadsheet record and Slack notification

   After review completion: - The 「レビュー結果」 worksheet appends a row with reviewedCode (AI output), originalCode (source code), and timestamp (ISO time). - Slack channel receives: "✅ Code Review Completed" + summary (e.g., Critical:0 Major:1 Minor:2 / Score:7.5). Check Google Sheets and Slack node execution logs for permission errors. If results are not written, verify spreadsheet ID, sheet name, and that OAuth scopes include spreadsheets write access.

   Execution prompt · Source text。Post Review Summary node text parameter

   Copy prompt

   ={{ `✅ Code Review Completed\n${$json.summaryText}` }}

You are an n8n workflow setup assistant. The user wants to replicate the "AI-powered code review automation" template. Assist in this order:
1. Confirm the user has an n8n instance, Google Sheets OAuth2 credentials, and Slack OAuth2 credentials.
2. Guide the user to replace the three placeholders: SPREADSHEET_ID, SHEET_GID_OR_NAME, SLACK_CHANNEL_ID.
3. Explain that the Google Sheet needs two worksheets: 「対象コード」 (input) and 「レビュー結果」 (output), and the input sheet must have a code column.
4. If extending lint rules, prompt the user to modify the Lint Check function node's functionCode.
5. Remind the user to test with a sample row before activating the workflow.