Make request headers immutable

[grahamlyons]

As mentioned in #32 the request headers in miniflare aren't immutable so I was able to introduce a bug that didn't get picked up until it was deployed.

Would you add a feature request to make these immutable so that my mistakes are picked up earlier?

Thanks so much for miniflare! It's changed my life.

Edit: this was actually on the response headers so perhaps that'll be two feature requests.

[mrbbot]

Hey! 👋 Glad you're liking Miniflare! 😊

I'm planning on switching to https://github.com/nodejs/undici for a more spec-compliant fetch implementation in version 2 which should solve this issue. Hang tight! 😄

[mrbbot]

Hey! 👋 The first pre-release of Miniflare 2 has just been released, which makes incoming Request headers immutable. You can find the full changelog here and install it with npm i miniflare@next -D. Please let me know if you have any other issues, and feel free to ask questions in the #miniflare channel of the Cloudflare Workers Discord server.