Implement Early Hints for modulepreload

[itsmatteomanf]

What this PR solves / how to test

This PR adds support for <link rel="modulepreload" href="..."> entries in the HTML, to allow them to be added to the Link header.

Author has addressed the following

• Tests
  • TODO (before merge)
  • Included
  • Not necessary because this feature is already not tested
• Changeset (Changeset guidelines)
  • TODO (before merge)
  • Included
  • Not necessary because:
• Public documentation
  • TODO (before merge)
  • Cloudflare docs PR(s): https://github.com/cloudflare/cloudflare-docs/pull/...
  • Not necessary because it's an expansion of the current feature set, which is already expected. Some more docs might be nice in general, but not related to this specific addition.

[changeset-bot]

🦋 Changeset detected

Latest commit: 6b823f7

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

This PR includes changesets to release 1 package

Name	Type
@cloudflare/pages-shared	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/9172210492/npm-package-wrangler-5674

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

npm install --save-dev https://prerelease-registry.devprod.cloudflare.dev/workers-sdk/prs/5674/npm-package-wrangler-5674

Or you can use npx with this latest build directly:

npx https://prerelease-registry.devprod.cloudflare.dev/workers-sdk/runs/9172210492/npm-package-wrangler-5674 dev path/to/script.js

Additional artifacts:

npx https://prerelease-registry.devprod.cloudflare.dev/workers-sdk/runs/9172210492/npm-package-create-cloudflare-5674 --no-auto-update

npm install https://prerelease-registry.devprod.cloudflare.dev/workers-sdk/runs/9172210492/npm-package-cloudflare-kv-asset-handler-5674

npm install https://prerelease-registry.devprod.cloudflare.dev/workers-sdk/runs/9172210492/npm-package-miniflare-5674

npm install https://prerelease-registry.devprod.cloudflare.dev/workers-sdk/runs/9172210492/npm-package-cloudflare-pages-shared-5674

npm install https://prerelease-registry.devprod.cloudflare.dev/workers-sdk/runs/9172210492/npm-package-cloudflare-vitest-pool-workers-5674

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

---

wrangler@3.57.0 includes the following runtime dependencies:

Package	Constraint	Resolved
miniflare	workspace:*	3.20240512.0
workerd	1.20240512.0	1.20240512.0
workerd --version	1.20240512.0	2024-05-12

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

[petebacondarwin]

Actually there are tests for this...

workers-sdk/packages/pages-shared/__tests__/asset-server/handler.test.ts

Line 520 in f514934

`"</a.png>; rel="preload"; as=image, </b.png>; rel="preload"; as=image"`

[itsmatteomanf]

@petebacondarwin I have merged the changes on main as there was a conflict, tell me if I red it wrong, but there is now a cache control header on the early hints cache, which makes sense, so merged it in here.

[itsmatteomanf]

Actually there are tests for this...

workers-sdk/packages/pages-shared/__tests__/asset-server/handler.test.ts

Line 520 in f514934

`"</a.png>; rel="preload"; as=image, </b.png>; rel="preload"; as=image"`

Does it make sense to test for the specific module preload part? The preconnect one isn't checked either...

[petebacondarwin]

I realised that we were not checking the linting on pages-shared, so I have just pushed an extra commit that cleans that up.
Meanwhile I think it is valuable to add a test for this new feature. It looks like it won't be too difficult. The fact that other features are not tested is not really a good argument for not testing new features.
I'm happy to add that test now, if you don't mind.

[itsmatteomanf]

I'm happy to add that test now, if you don't mind.

Might make sense to just add the preconnect test, too? It's not hard to do and would cover all cases, should I or should you?

[petebacondarwin]

I'm happy to add that test now, if you don't mind.

Might make sense to just add the preconnect test, too? It's not hard to do and would cover all cases, should I or should you?

If you have time, please do. Thanks.

[petebacondarwin]

Added a small fixup commit because some snapshot tests needed updating. But otherwise looks good. We just need a review from a pages team member and then we are good to merge.

[WalshyDev]

I'll get this released along with #5875 hopefully tomorrow or Thursday @itsmatteomanf
Appreciate it!