[miniflare] fix: ensure redirects handled correctly with dispatchFetch()

[mrbbot]

What this PR solves / how to test

Fixes #5018.

Previously, if your Worker returned a redirect response, calling dispatchFetch(url) would send another request to the original url rather than the redirect. This happened because...

1. We always used this.#runtimeDispatcher for fetch()ing, which only sends request to the runtime. This meant if a Worker returned a redirect to a different origin, that origin would be ignored and the request would still go to the runtime.
2. The MF-Original-URL header was not cleared/modified during redirects. This meant if a Worker returned a relative/absolute redirect to the same runtime origin, the path would not be updated in the request received by the user.

This change ensures redirects are followed correctly.

• If your Worker returns a relative redirect or an absolute redirect with the same origin as the original url, the request will be sent to the Worker.
• If your Worker instead returns an absolute redirect with a different origin, the request will be sent to the Internet.
• If a redirected request to a different origin returns an absolute redirect with the same origin as the original url, the request will also be sent to the Worker.

Tests have been added to cover the different types of redirect. 👍

Author has addressed the following

• Tests
  • TODO (before merge)
  • Included
  • Not necessary because:
• Changeset (Changeset guidelines)
  • TODO (before merge)
  • Included
  • Not necessary because:
• Public documentation
  • TODO (before merge)
  • Cloudflare docs PR(s):
  • Not necessary because: redirects working is expected behaviour 😅

[changeset-bot]

🦋 Changeset detected

Latest commit: da7ad8f

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 4 packages

Name	Type
miniflare	Patch
@cloudflare/pages-shared	Patch
@cloudflare/vitest-pool-workers	Patch
wrangler	Patch

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[github-actions]

A wrangler prerelease is available for testing. You can install this latest build in your project with:

npm install --save-dev https://prerelease-registry.devprod.cloudflare.dev/workers-sdk/runs/8186988941/npm-package-wrangler-5191

You can reference the automatically updated head of this PR with:

npm install --save-dev https://prerelease-registry.devprod.cloudflare.dev/workers-sdk/prs/5191/npm-package-wrangler-5191

Or you can use npx with this latest build directly:

npx https://prerelease-registry.devprod.cloudflare.dev/workers-sdk/runs/8186988941/npm-package-wrangler-5191 dev path/to/script.js

Additional artifacts:

npx https://prerelease-registry.devprod.cloudflare.dev/workers-sdk/runs/8186988941/npm-package-create-cloudflare-5191 --no-auto-update

npm install https://prerelease-registry.devprod.cloudflare.dev/workers-sdk/runs/8186988941/npm-package-cloudflare-kv-asset-handler-5191

npm install https://prerelease-registry.devprod.cloudflare.dev/workers-sdk/runs/8186988941/npm-package-miniflare-5191

npm install https://prerelease-registry.devprod.cloudflare.dev/workers-sdk/runs/8186988941/npm-package-cloudflare-pages-shared-5191

npm install https://prerelease-registry.devprod.cloudflare.dev/workers-sdk/runs/8186988941/npm-package-cloudflare-vitest-pool-workers-5191

Note that these links will no longer work once the GitHub Actions artifact expires.

---

[email protected] includes the following runtime dependencies:

Package	Constraint	Resolved
miniflare	workspace:*	3.20240223.1
workerd	1.20240304.0	1.20240304.0
workerd --version	1.20240304.0	2024-03-04

Please ensure constraints are pinned, and miniflare/workerd minor versions match.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.37%. Comparing base (84eeee5) to head (da7ad8f).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5191      +/-   ##
==========================================
+ Coverage   70.35%   70.37%   +0.02%     
==========================================
  Files         298      298              
  Lines       15567    15567              
  Branches     4007     4007              
==========================================
+ Hits        10952    10956       +4     
+ Misses       4615     4611       -4     

see 5 files with indirect coverage changes