Node polyfills

[Rich-Harris]

This replaces @sveltejs/kit/install-fetch with @sveltejs/kit/node/polyfills, and adds crypto to the list of web APIs that are guaranteed to be present.

• add AbortController (prevent scroll when resetting page focus (#4065) #4846)
• add web streams (Handling streaming request/response bodies #3419)
• add other interfaces listed on Minimum Common Web Platform API? if we wanted to get really sophisticated we'd detect which APIs were used, so that adapters could only bundle those
• swap out node-fetch for undici, which is more standards compliant (though I think we're blocked on Undici strips out set-cookie headers, even when "credentials: 'include'" is set nodejs/undici#1262)
• only add polyfills if they're not already there (since Node 18 provides a lot of stuff anyway. in future maybe we should have @sveltejs/kit/node/polyfills/16 and @sveltejs/kit/node/polyfills/18)
• document which APIs are guaranteed to be present

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[changeset-bot]

🦋 Changeset detected

Latest commit: 453bc68

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

This PR includes changesets to release 4 packages

Name	Type
@sveltejs/adapter-netlify	Patch
@sveltejs/adapter-node	Patch
@sveltejs/adapter-vercel	Patch
@sveltejs/kit	Patch

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[ghostdevv]

Will this mean that libraries that rely on node dependencies in a non-node environment such as CloudFlare Pages have a chance of working? i.e. stripe

[Rich-Harris]

No, it's the opposite — it's bringing the Node environment up to date with other more web-like ones, where fetch and crypto etc are already universally supported. If people need to use Node-specific dependencies in non-Node environments, they will need to use things like https://www.npmjs.com/package/rollup-plugin-node-builtins (though some of these have significant caveats).

Ideally, those libraries should be updated to use web APIs, instead of assuming they're running in Node.

[benmccann]

Just FYI, Vite is likely switching to node-native-fetch: vitejs/vite#8157

[Rich-Harris]

We really need to use undici, since that unblocks #3419 — node-fetch-native won't work for us

[Rich-Harris]

Added crypto to the web standards section of the docs, so marking this ready for review. The other stuff (upgrading to undici, etc) can wait until another time, no point waiting on that for everything else.