PR Review and CI Fixes

Use This Skill When

• Reviewing CI failures on pull requests
• Diagnosing test failures
• Fixing linting or type check errors
• Resolving build failures
• Understanding security scan results
• Unblocking stalled PRs due to CI issues

When NOT to Use

• Pre-PR testing (run locally first)
• Infrastructure issues (not PR-level)
• Flaky test investigation (broader scope)

Context: CI Fix Capability Maturity

Undeveloped: CI failures unclear; don't know how to fix.

Target: Read CI logs, identify root cause, apply fix.

Optimized: Automated CI fixes, pattern detection, preventive changes.

Core Principle

CI failures are clues, not blockers. Understanding CI output and common error patterns enables quick diagnosis and fixes.

Instructions

Step 1: Understand CI System

Identify the CI system:

System	Log Location	Re-run
GitHub Actions	Actions tab on PR	"Re-run jobs"
GitLab CI	CI/CD → Pipelines	Re-run button
Jenkins	Build console	"Build Again"
CircleCI	Checks tab	Rerun workflow

Step 2: Read CI Logs

Locate and analyze logs:

❌ FAILED: Run tests
  → Look for: error message, stack trace, failed test name
  → Key info: Where exactly did it fail?

Example output:
  FAIL  tests/calculator.test.js
  ● Calculator › should add numbers correctly
    Expected: 5
    Received: NaN
    at test (tests/calculator.test.js:12:5)

Step 3: Categorize Failure Type

Common CI failures:

Type	Example	Fix
Test Failure	"Expected: 5, Received: NaN"	Fix code to match expectation
Linting Error	"Unexpected token ';'"	Run linter locally, fix issues
Type Error	"Cannot find property 'x' on type 'any'"	Add type annotations
Build Error	"Module not found: 'react'"	Install missing dependencies
Security Scan	"High severity: SQL injection"	Fix vulnerability

Step 4: Test Failure Diagnosis

Common test issues:

## Test Failure: "Expected 5, Received NaN"

### Root Cause Analysis

**Step 1**: Identify test file location
- File: tests/calculator.test.js, Line 12

**Step 2**: Review test code
```javascript
test('should add numbers correctly', () => {
  const result = add(2, 3);
  expect(result).toBe(5);  // Line 12 failing here
});

Step 3: Review implementation

function add(a, b) {
  return a + b;  // Currently returns NaN
}

Step 4: Identify issue

• Function returns NaN when called with (2, 3)
• Check: Are parameters being parsed as numbers? Strings?
• Possible fix: return Number(a) + Number(b);

Step 5: Fix and verify locally

npm test tests/calculator.test.js
# ✓ Test passes
# Push fix

### Step 5: Linting Error Fixes

**Common linting issues:**

```markdown
## Linting Error: "Unexpected token ';'"

### Common Causes
- Extra semicolon: Remove
- Missing semicolon: Add
- Quote mismatch: Use consistent quotes
- Unused variable: Remove or use variable

### Auto-fix
```bash
npm run lint -- --fix
# Automatically fixes 80% of errors

### Step 6: Type Check Errors

**TypeScript/Flow issues:**

```markdown
## Type Error: "Cannot find property 'x' on type 'any'"

### Root Cause
- Variable typed as 'any' but property not guaranteed
- Solution: Add proper type annotation

### Fix
```typescript
// Before
const user: any = getUser();
console.log(user.email);  // TS error

// After
interface User {
  id: number;
  email: string;
}

const user: User = getUser();
console.log(user.email);  // TS OK

### Step 7: Build/Dependency Errors

**Module not found errors:**

```markdown
## Build Error: "Module not found: 'react'"

### Causes
- Package not installed
- Wrong import path
- Version conflict

### Fix
```bash
# Check if package is installed
npm list react

# If not, install it
npm install react

# If installed but not found, try clean install
rm package-lock.json node_modules/
npm install

# If import path wrong:
# Change: import React from 'react-dom'  ❌
# To:     import React from 'react'      ✓

### Step 8: Security Scan Failures

**Fix security vulnerabilities:**

```markdown
## Security: "SQL injection vulnerability"

### Scan Output

CRITICAL: SQL injection in queries.js:12 const query = SELECT * FROM users WHERE id = ${userId} ^^^^^^ Risk: User input directly in SQL

### Fix
```javascript
// Before (vulnerable)
const query = `SELECT * FROM users WHERE id = ${userId}`;
db.run(query);

// After (safe)
const query = 'SELECT * FROM users WHERE id = ?';
db.run(query, [userId]);  // Parameterized query

### Step 9: Check If PR Needs Changes

**Once logs are analyzed, determine next step:**

```markdown
## CI Fix Decision Tree

1. **Is the error in my code?**
   - Yes → Fix it
   - No → Check dependencies

2. **Did I add a new dependency?**
   - Yes → Verify package-lock.json is committed
   - No → Proceed

3. **Is the test failing?**
   - Yes → Review test logic
   - No → Check environment setup

4. **Can I reproduce locally?**
   - Yes → Fix locally, push
   - No → Might be environment issue; check CI config

Common Fix Checklist

• Read full CI log (not just error summary)
• Identify failure type (test/lint/type/build/security)
• Reproduce issue locally
• Apply fix
• Run test/check locally to verify
• Push changes
• Monitor CI rerun

Output

Deliver:

1. Failure Diagnosis (root cause identified)
2. Fix Applied (code changes committed)
3. Verification (CI passing, test passing locally)
4. Documentation (if issue was non-obvious)