# MegaLinter Local Execution Guide
This guide provides instructions for running MegaLinter locally on your development machine.
## Quick Start
### Option 1: Docker (Recommended)
Run MegaLinter using the official Docker image:
```bash
docker run --rm \
-v $(pwd):/tmp/lint \
-e VALIDATE_ALL_CODEBASE=true \
-e APPLY_FIXES=all \
oxsecurity/megalinter-javascript:v7
```
### Option 2: npx (Fast)
Run MegaLinter directly with npx (no Docker required):
```bash
npx mega-linter-runner --flavor javascript
```
### Option 3: Install Globally
Install MegaLinter globally for repeated use:
```bash
npm install -g mega-linter-runner
mega-linter-runner --flavor javascript
```
## Common Commands
### Run with Auto-Fix
Apply automatic fixes to your code:
```bash
docker run --rm \
-v $(pwd):/tmp/lint \
-e APPLY_FIXES=all \
oxsecurity/megalinter-javascript:v7
```
### Run Specific Linters Only
Run only JavaScript/TypeScript linters:
```bash
docker run --rm \
-v $(pwd):/tmp/lint \
-e ENABLE=JAVASCRIPT,TYPESCRIPT \
oxsecurity/megalinter-javascript:v7
```
Run only security linters:
```bash
docker run --rm \
-v $(pwd):/tmp/lint \
-e ENABLE=DOCKERFILE,TERRAFORM \
oxsecurity/megalinter-javascript:v7
```
### Run on Specific Files/Directories
Lint only the src directory:
```bash
docker run --rm \
-v $(pwd)/src:/tmp/lint/src \
oxsecurity/megalinter-javascript:v7
```
### Generate Detailed Reports
Run with all reporters enabled:
```bash
docker run --rm \
-v $(pwd):/tmp/lint \
-e FORMATTERS_DISABLE_ERRORS=true \
-e TEXT_REPORTER=true \
-e JSON_REPORTER=true \
-e SARIF_REPORTER=true \
oxsecurity/megalinter-javascript:v7
```
## Pre-Commit Hook Setup
### Using Husky
Install Husky and create a pre-commit hook:
```bash
npm install --save-dev husky
npx husky install
npx husky add .husky/pre-commit "npx mega-linter-runner --flavor javascript --files \$1"
```
### Using Git Hooks Directly
Create `.git/hooks/pre-commit`:
```bash
#!/bin/bash
npx mega-linter-runner --flavor javascript --files $(git diff --cached --name-only)
```
Make it executable:
```bash
chmod +x .git/hooks/pre-commit
```
## IDE Integration
### VS Code
Install the MegaLinter extension:
1. Open VS Code
2. Go to Extensions (Ctrl+Shift+X)
3. Search for "MegaLinter"
4. Install "MegaLinter by Nicolas Vuillamy"
5. Run "MegaLinter: Lint Workspace" from Command Palette (Ctrl+Shift+P)
### JetBrains IDEs (IntelliJ, WebStorm)
Configure as an External Tool:
1. Go to Settings → Tools → External Tools
2. Click "+" to add new tool
3. Name: "MegaLinter"
4. Program: `docker`
5. Arguments: `run --rm -v $ProjectFileDir$:/tmp/lint oxsecurity/megalinter-javascript:v7`
6. Working directory: `$ProjectFileDir$`
## Performance Optimization
### Use Flavor for Faster Execution
The project uses the `javascript` flavor, which is optimized and ~3x faster than the full MegaLinter:
```bash
# Fast (javascript flavor - 68 linters)
docker run --rm -v $(pwd):/tmp/lint oxsecurity/megalinter-javascript:v7
# Slow (full flavor - 120+ linters)
docker run --rm -v $(pwd):/tmp/lint oxsecurity/megalinter:v7
```
### Validate Only Changed Files
```bash
export VALIDATE_ALL_CODEBASE=false
npx mega-linter-runner --flavor javascript
```
### Use Caching
MegaLinter automatically caches results in `.megalinter/` directory. Keep this directory to speed up subsequent runs.
## Linter-Specific Commands
### ESLint Only
```bash
npm run lint
# or with auto-fix
npm run lint:fix
```
### Prettier Only
```bash
npm run format
```
### TypeScript Type Checking
```bash
npm run typecheck
```
### Dockerfile Linting
```bash
docker run --rm -i hadolint/hadolint < Dockerfile
```
### Terraform Validation
```bash
cd terraform/
terraform init
terraform validate
tflint
```
### npm Security Audit
```bash
npm audit
# or fix automatically
npm audit fix
```
## Troubleshooting
### Docker Permission Issues
If you encounter permission issues with Docker:
```bash
# Linux/macOS
docker run --rm -v $(pwd):/tmp/lint -u $(id -u):$(id -g) oxsecurity/megalinter-javascript:v7
# Windows (PowerShell)
docker run --rm -v ${PWD}:/tmp/lint oxsecurity/megalinter-javascript:v7
```
### Out of Memory Errors
Increase Docker memory allocation or disable resource-intensive linters:
```bash
docker run --rm -v $(pwd):/tmp/lint -m 4g oxsecurity/megalinter-javascript:v7
```
### Slow Performance
1. Use the `javascript` flavor (already configured)
2. Enable parallel execution: `PARALLEL=true`
3. Disable unused linters in `.mega-linter.yml`
4. Use `VALIDATE_ALL_CODEBASE=false` for incremental linting
## Configuration Files
The following configuration files are used:
- `.mega-linter.yml` - Main MegaLinter configuration
- `.eslintrc.cjs` - ESLint rules
- `.prettierrc` - Prettier formatting rules
- `.prettierignore` - Prettier ignore patterns
- `.hadolint.yaml` - Dockerfile linting rules
- `.tflint.hcl` - Terraform linting rules
- `.yamllint.yml` - YAML linting rules
- `.markdownlint.json` - Markdown linting rules
- `.cspell.json` - Spell checking dictionary
- `.jscpd.json` - Copy-paste detection config
## Continuous Integration
The GitHub Actions workflow runs automatically on:
- Pull requests to `main` branch
- Pushes to `main` branch
- Daily at 2 AM UTC (scheduled security scans)
- Manual trigger via workflow dispatch
## Expected Runtime
| Execution Mode | Estimated Time | Notes |
|---------------|----------------|-------|
| Local (incremental) | 30-60 seconds | Only changed files |
| Local (full scan) | 2-4 minutes | All files |
| CI/CD (PR) | 3-5 minutes | With npm install + caching |
| CI/CD (main) | 4-6 minutes | Full validation |
| Security scan (scheduled) | 5-8 minutes | Includes Trivy container scan |
## Resources
- [MegaLinter Documentation](https://megalinter.io/)
- [Supported Linters](https://megalinter.io/latest/supported-linters/)
- [Configuration Options](https://megalinter.io/latest/configuration/)
- [GitHub Actions Integration](https://megalinter.io/latest/install-assisted/#github-actions)
