bun-ready

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CLI that estimates whether a repository will "survive" migrating to Bun — quickly.
It inspects package.json, lockfiles, scripts, and can run bun install --dry-run in a temp directory. It then generates a green / yellow / red Markdown report with reasons.

Why

Bun moves fast. People need a fast risk signal before they try to migrate a repo.

Install

Run without installing (recommended)

bunx bun-ready scan .

Install globally

bun install -g bun-ready
bun-ready scan .

Usage

bun-ready scan <path> [--format md|json|sarif] [--out <file>] [--no-install] [--no-test] [--verbose] [--detailed] [--scope root|packages|all] [--fail-on green|yellow|red] [--ci] [--output-dir <dir>] [--rule <id>=<action>] [--max-warnings <n>] [--baseline <file>] [--update-baseline] [--changed-only] [--since <ref>]

Examples:

bun-ready scan .
bun-ready scan . --out bun-ready.md
bun-ready scan ./packages/api --format json
bun-ready scan . --no-install --no-test
bun-ready scan . --detailed

Exit codes

• 0 → GREEN
• 2 → YELLOW
• 3 → RED

Monorepo / Workspaces Support

bun-ready now supports scanning monorepo projects with multiple workspace packages.

Workspace Discovery

If your package.json contains a workspaces field (array or object), bun-ready will:

• Discover all workspace packages automatically
• Analyze each package individually
• Aggregate results into a single report

Configuration

You can create a bun-ready.config.json file in your repository root to customize the scan:

{
  "ignorePackages": ["packages/legacy"],
  "ignoreFindings": ["scripts.pm_assumptions"],
  "nativeAddonAllowlist": ["fsevents"],
  "failOn": "yellow"
}

Options

| Option | Description | Default | |---------|-------------|----------| | ignorePackages | Array of package paths to ignore | [] | | ignoreFindings | Array of finding IDs to ignore | [] | | nativeAddonAllowlist | Packages to exclude from native addon checks | [] | | failOn | When to return non-zero exit code | "red" | | detailed | Enable detailed package usage analysis | false |

New CLI Flags

--scope root|packages|all

• root: Scan only the root package.json
• packages: Scan only workspace packages
• all: Scan root and all workspace packages (default)

--fail-on green|yellow|red

• Controls when bun-ready exits with a failure code
• green: Fail on anything not green (exit 3)
• yellow: Fail on red only (exit 3), yellow passes (exit 0)
• red: Default behavior - green=0, yellow=2, red=3

--detailed

• Enables detailed package usage analysis
• Shows which packages are used in which files
• Provides file-by-file breakdown of imports
• Output is written to bun-ready-detailed.md instead of bun-ready.md
• Requires scanning of all .ts, .js, .tsx, .jsx files in the project
• Note: This operation is slower as it needs to read and parse all source files

Detailed Reports

When using the --detailed flag, bun-ready provides comprehensive package usage information:

What it analyzes:

• All source files with extensions: .ts, .js, .tsx, .jsx, .mts, .mjs
• Import patterns supported:
  • ES6 imports: import ... from 'package-name'
  • Namespace imports: import * as name from 'package-name'
  • Dynamic imports: import('package-name')
  • CommonJS requires: require('package-name')
• Local imports (starting with ./ or ../) are ignored
• Skips node_modules and hidden directories

Output format:

The detailed report shows:

1. Package Summary - Total files analyzed and packages used
2. Per-package usage - For each package in your dependencies:
   • How many files import it
   • List of all file paths where it's used
3. Regular findings - All migration risk findings from standard analysis

Example:

bun-ready scan . --detailed

This generates bun-ready-detailed.md with sections like:

### @nestjs/common (15 files)
- src/main.ts
- src/app.module.ts
- src/auth/auth.service.ts
...

Configuration:

You can also enable detailed reports via config file:

{
  "detailed": true
}

When detailed is set in config, it acts as if --detailed was passed, unless overridden by CLI flags.

How Scoring Works

bun-ready uses a combination of heuristics to determine migration readiness:

Severity Levels

🟢 GREEN - Ready to migrate

• No critical issues detected
• Bun install succeeds
• Tests pass (if compatible)
• No native addon risks or properly handled

🟡 YELLOW - Migration possible with manual fixes

• Lifecycle scripts present (verify npm compatibility)
• Native addons detected (may need updates)
• Package manager assumptions in scripts
• Node version < 18
• Dev tools that may need configuration

🔴 RED - Migration blocked

• Bun install fails
• Native build tools (node-gyp, node-sass)
• Critical missing dependencies
• Tests fail

Findings Categories

• scripts.lifecycle - Lifecycle scripts in root or dependencies
• scripts.npm_specific - npm/yarn/pnpm-specific commands
• scripts.pm_assumptions - Package manager assumptions
• deps.native_addons - Native addon dependencies
• runtime.node_version - Node.js version requirements
• runtime.dev_tools - Testing frameworks (jest, vitest, etc.)
• runtime.build_tools - Build tools (webpack, babel, etc.)
• runtime.ts_execution - TypeScript runtime execution
• lockfile.missing - No lockfile detected
• lockfile.migration - Non-Bun lockfile present
• install.blocked_scripts - Scripts blocked by Bun
• install.trusted_deps - Trusted dependencies mentioned

FAQ

Why yellow when there's a postinstall script?

Bun runs your project's lifecycle scripts during install, but does not run lifecycle scripts of dependencies unless they're in trustedDependencies. The yellow warning reminds you to verify these scripts work correctly with Bun.

What are trustedDependencies?

Bun's trustedDependencies configuration controls which packages are allowed to run their lifecycle scripts. You can add trusted packages to this field in your package.json:

{
  "trustedDependencies": ["some-package"]
}

How do I handle monorepo scanning?

For monorepos, bun-ready automatically detects workspaces and scans all packages. Use --scope to control what's scanned:

# Scan everything (default)
bun-ready scan .

# Scan only root package
bun-ready scan . --scope root

# Scan only workspace packages
bun-ready scan . --scope packages

Can I ignore certain findings?

Yes! Create a bun-ready.config.json file:

{
  "ignoreFindings": ["scripts.pm_assumptions"]
}

What if a package is in the native addon list but works with Bun?

Add it to the allowlist:

{
  "nativeAddonAllowlist": ["fsevents"]
}

Some packages have optional native modules that can be disabled or work fine with Bun.

v0.3 New Features

CI Mode

Run in CI mode for stable, machine-friendly output:

bun-ready scan . --ci --output-dir .bun-ready-artifacts

CI Mode Benefits:

• Reduced "human noise" in stdout
• Stable section ordering in reports
• CI summary block with top findings and next actions
• Automatic artifact generation when --output-dir is specified

SARIF Export

Generate SARIF 2.1.0 format for GitHub Code Scanning:

bun-ready scan . --format sarif --out bun-ready.sarif.json

Policy-as-Code

Enforce organization-specific migration policies:

# CLI flags
bun-ready scan . --rule deps.native_addons=fail --max-warnings 5

# Or in config file
{
  "rules": [
    { "id": "deps.native_addons", "action": "fail" },
    { "id": "scripts.lifecycle", "action": "off" }
  ],
  "thresholds": {
    "maxWarnings": 10,
    "maxPackagesRed": 2
  }
}

Policy Sources (priority order):

1. CLI flags (--rule, --max-warnings)
2. bun-ready.config.json file
3. Default rules

Policy Actions:

• fail - Mark finding as failure
• warn - Downgrade to warning
• off - Disable this finding
• ignore - Ignore this finding (don't report)

Baseline / Regression Detection

Prevent regressions by comparing against a baseline:

# Create baseline (first time)
bun-ready scan . --baseline bun-ready-baseline.json --update-baseline

# In CI - compare against baseline
bun-ready scan . --baseline bun-ready-baseline.json --ci

Baseline Features:

• Detects new findings
• Detects resolved findings
• Detects severity changes (upgrades/downgrades)
• Regression verdict: fails if new red findings or increased failures
• Update baseline with --update-baseline

Changed-Only Scanning (Monorepos)

Scan only changed packages to speed up large monorepo PRs:

bun-ready scan . --changed-only --since main

Changed-Only Verdict Types:

• Partial verdict (no baseline): Warning about partial coverage
• Regression verdict (with baseline): OK - comparing only changed packages

GitHub Action Integration

Use bun-ready as a GitHub Action:

name: bun-ready Check
on: [pull_request]
jobs:
  bun-ready:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: oven-sh/setup-bun@v1
      - uses: ./  # Uses action.yml from repo
        with:
          fail-on: yellow
          baseline: bun-ready-baseline.json

Action Features:

• Automatic artifact upload
• GitHub job summary generation
• PR comment support
• SARIF export for Code Scanning
• Policy and baseline support

v0.4 New Features - Extended Analysis

Node.js API Compatibility Analysis

Analyze your codebase for Node.js built-in module usage and Bun compatibility:

# Enable full extended analysis
bun-ready scan . --extended
bun-ready scan . -x  # shorthand

# Selective analysis
bun-ready scan . --analyze api       # Only API analysis
bun-ready scan . --analyze modules   # Only module analysis

Module Compatibility Zones:

| Zone | Description | Examples | |------|-------------|----------| | 🟢 Green | Fully compatible | fs, path, crypto, events, stream | | 🟡 Yellow | Partial differences | child_process, http, worker_threads | | 🔴 Red | Limited support | vm, v8, inspector, wasi |

New Finding IDs:

• api.node_builtins - Node.js built-in modules detected
• api.node_prefix - Recommendation to use node: prefix
• modules.esm_cjs_mixed - Mixed ESM/CJS imports
• modules.cjs_globals - CJS globals (__dirname, __filename)

What it checks (MVP)

• package.json presence & shape
• lockfiles (npm/yarn/pnpm/bun)
• scripts (postinstall/prepare, npm-specific patterns)
• heuristics for native addons / node-gyp risk
• optional: bun install --dry-run in a temp dir
• optional: bun test if tests appear Bun-compatible

Contributing

See CONTRIBUTING.md. For security issues, see SECURITY.md.

Support

If this tool saves you time, consider supporting:

• Ko-fi: https://ko-fi.com/pas7studio
• PayPal: https://www.paypal.com/ncp/payment/KDSSNKK8REDM8

About Pas7 Studio

bun-ready is developed and maintained by Pas7 Studio, a software development company specializing in modern JavaScript/TypeScript solutions, runtime migrations, and developer tools.

Why Bun?

Interested in migrating from Node.js to Bun? Read our article on Bun vs Node.js in 2026 to understand the benefits, challenges, and best practices for making the switch.

Need Help?

If you need assistance with:

• 🚀 Bun migration for your projects
• 🔧 Custom development and consulting
• 📊 Team training on modern runtimes

Contact Pas7 Studio - we're here to help!

Links

• 🌐 Website: https://pas7.com.ua/
• 📧 Contact: https://pas7.com.ua/contact
• 📝 Blog: Bun vs Node.js 2026
• 💼 LinkedIn: Pas7 Studio