node-to-bun

Node.js to Bun Migration

You are assisting with migrating an existing Node.js project to Bun. This involves analyzing dependencies, updating configurations, and ensuring compatibility.

Migration Workflow

1. Pre-Migration Analysis

Check if Bun is installed:

bun --version

Analyze current project:

# Check Node.js version
node --version

# Check package manager
ls -la | grep -E "package-lock.json|yarn.lock|pnpm-lock.yaml"

Read package.json to understand the project structure.

2. Dependency Compatibility Check

Read and analyze all dependencies from package.json:

cat package.json

Check for known incompatible native modules:

Common problematic packages (check against current dependencies):

• bcrypt → Use bcryptjs or @node-rs/bcrypt instead
• sharp → Bun has native support, but may need version check
• node-canvas → Limited support, check version compatibility
• sqlite3 → Use bun:sqlite instead
• node-gyp dependent packages → May require alternative pure JS versions
• fsevents → macOS-specific, usually optional dependency
• esbuild → Bun has built-in bundler, may be redundant

Check workspace configuration (for monorepos):

# Check if workspaces are defined
grep -n "workspaces" package.json

3. Generate Compatibility Report

Create a migration report file BUN_MIGRATION_REPORT.md:

# Bun Migration Analysis Report

## Project Overview
- **Name**: [project name]
- **Current Node Version**: [version]
- **Package Manager**: [npm/yarn/pnpm]
- **Project Type**: [app/library/monorepo]

## Dependency Analysis

### ✅ Compatible Dependencies
[List dependencies that are Bun-compatible]

### ⚠️ Potentially Incompatible Dependencies
[List dependencies that may have issues]

**Recommended Actions:**
- [Specific migration steps for each incompatible dependency]

### 🔄 Recommended Replacements
[List suggested package replacements]

## Configuration Changes Needed

### package.json
- [ ] Update scripts to use `bun` instead of `npm`/`yarn`
- [ ] Review and update `engines` field
- [ ] Check `type` field (ESM vs CommonJS)

### tsconfig.json
- [ ] Update `moduleResolution` to `"bundler"`
- [ ] Add `bun-types` to types array
- [ ] Set `allowImportingTsExtensions` to `true`

### Build Configuration
- [ ] Review webpack/rollup/esbuild config (may use Bun bundler)
- [ ] Update test runner config (use Bun test instead of Jest)

## Migration Steps

1. Install Bun dependencies
2. Update configuration files
3. Run tests to verify compatibility
4. Update CI/CD pipelines
5. Update documentation

## Risk Assessment

**Low Risk:**
[List low-risk changes]

**Medium Risk:**
[List items needing testing]

**High Risk:**
[List critical compatibility concerns]