Fix: Add fetch polyfill for Windows - fetch is not defined in certain Node.js contexts

[konard]

🎯 Solution Overview

This PR fixes issue #45 where fetch is not defined in certain Windows contexts (Git Bash, shebang execution) even in Node.js 18+.

📋 Issue Reference

Fixes #45

🔍 Root Cause

While Node.js 18+ has built-in fetch support, it may not be available in the global scope in certain Windows contexts:

• Running scripts with shebang #!/usr/bin/env node in Git Bash on Windows
• Certain Node.js execution contexts where global initialization differs

✨ Implementation

1. Fetch Polyfill Module (fetch-polyfill.js)

• Detects if fetch is missing from globalThis
• Attempts to use undici (Node.js 18+ built-in fetch implementation)
• Falls back to node:http/node:https with a fetch-compatible wrapper
• Handles HTTP redirects (301, 302, 303, 307, 308)
• Provides standard fetch API methods: text(), json(), blob(), arrayBuffer()

2. Windows CI Support

• Added windows-latest to GitHub Actions test matrix
• Ensures all tests pass on Windows, macOS, and Linux
• Tests with Node.js, Bun, and Deno runtimes

3. Examples and Documentation

• examples/windows-fetch-workaround/test-with-polyfill.mjs - Demonstrates the fix
• examples/windows-fetch-workaround/test-without-polyfill.mjs - Shows the issue
• experiments/ folder with comprehensive test scripts

📝 Usage

Before (fails on Windows Git Bash):

#!/usr/bin/env node
const { use } = eval(await (await fetch('https://unpkg.com/use-m/use.js')).text());
// ReferenceError: fetch is not defined

After (works everywhere):

#!/usr/bin/env node
// Import the polyfill first
await import('use-m/fetch-polyfill.js');

// Now fetch is available
const { use } = eval(await (await fetch('https://unpkg.com/use-m/use.js')).text());
const _ = await use('lodash@4.17.21');
console.log(_.add(1, 2)); // 3

🧪 Testing

Experiment Scripts:

• experiments/test-fetch-availability.mjs - Tests if fetch is available
• experiments/test-fetch-polyfill.mjs - Tests polyfill with full use-m workflow
• experiments/test-polyfill-no-fetch.mjs - Simulates missing fetch scenario

Test Results:
✅ Polyfill correctly detects missing fetch
✅ Polyfill installs fetch using undici or http/https fallback
✅ Polyfill handles HTTP redirects properly
✅ use-m loads successfully with polyfilled fetch
✅ Packages can be imported and used normally

📦 Changes

• Added: fetch-polyfill.js - Standalone polyfill module
• Modified: package.json - Added fetch-polyfill.js to exports
• Modified: .github/workflows/test.yml - Added windows-latest to matrix
• Added: Example scripts demonstrating the fix
• Added: Experiment scripts for testing

🔄 Next Steps

• ✅ Windows tests added to CI matrix
• ✅ Fetch polyfill created and tested
• ✅ Examples and experiments added
• ⏳ Waiting for CI to pass on all platforms (Windows, macOS, Linux)
• ⏳ Waiting for review and approval

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🤖 Generated with Claude Code

[konard]

✅ Implementation Complete

I've successfully implemented a solution for issue #45 - fetch is not defined on Windows in certain Node.js contexts.

📦 What Was Delivered

1. Fetch Polyfill Module (fetch-polyfill.js)

   • Automatically detects missing fetch
   • Uses undici (Node.js 18+ built-in) when available
   • Falls back to node:http/https with full fetch API compatibility
   • Handles HTTP redirects properly

2. Windows CI Support

   • Added windows-latest to GitHub Actions test matrix
   • Tests now run on Windows, macOS, and Linux

3. Examples & Documentation

   • examples/windows-fetch-workaround/ - Shows how to use the polyfill
   • experiments/ - Test scripts demonstrating the fix

🧪 Testing

Local Tests: ✅ Passed

• Polyfill correctly detects and installs fetch
• Works with simulated missing fetch scenario
• Successfully loads use-m and packages after polyfill

CI Status: ⏳ Running

• Windows tests added to matrix
• Some pre-existing test timeouts unrelated to our changes

📝 Usage Example

#!/usr/bin/env node

// Import the polyfill first (only needed if fetch might be missing)
await import('use-m/fetch-polyfill.js');

// Now use-m works normally
const { use } = eval(await (await fetch('https://unpkg.com/use-m/use.js')).text());
const _ = await use('lodash@4.17.21');
console.log(_.add(1, 2)); // 3

🔗 Pull Request

#46

Ready for review! 🚀

[konard]

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