Provide AbortController implementation for load({ fetch })

[furudean]

Describe the problem

The preferred way to set up timeouts with fetch is to use AbortController. This is a browser API that does not exist in most supported node versions (or other environments) and requires a user provided polyfill to work correctly. abort-controller is what node-fetch suggests as a solution.

The user has to handle both the browser and ssr rendering cases with something like:

const AbortController = globalThis.AbortController || await import('abort-controller')

This is awkward, and I think it's in the spirit of Svelte Kit to help out with this.

Describe the proposed solution

Expose a polyfilled AbortController implementation as a parameter like we did with fetch, i.e. load({ fetch, AbortController }), or as a global.

Alternatives considered

Bring your own polyfill and set up logic yourself.

Importance

would make my life easier

Additional Information

No response

[Rich-Harris]

Yeah, agree with this. Now that WinterCG exists, we could look to this document for guidance on which APIs should be available. install-fetch probably needs to become something like install-runtime (and maybe we need to have different versions of it for different Node versions, since future versions of Node will include more of this stuff).

[Rich-Harris]

Actually, looking at https://developer.mozilla.org/en-US/docs/Web/API/AbortController#browser_compatibility, AbortController is supported in Node in versions 15 and above. As of #4922, SvelteKit only supports Node 16 and above, which means we can guarantee that AbortController is present - no polyfills needed.

[furudean]

What about other environments?

[abdo643-HULK]

What about other environments?

Deno and cloudflare have out of the box support and all other environments officially supported by the sveltekit team run on aws lambda which gets defaulted into using Node 16.