File size: 2,754 Bytes
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let registry: FinalizationRegistry<WeakRef<ReadableStream>> | undefined
if (globalThis.FinalizationRegistry) {
registry = new FinalizationRegistry((weakRef: WeakRef<ReadableStream>) => {
const stream = weakRef.deref()
if (stream && !stream.locked) {
stream.cancel('Response object has been garbage collected').then(noop)
}
})
}
/**
* Clones a response by teeing the body so we can return two independent
* ReadableStreams from it. This avoids the bug in the undici library around
* response cloning.
*
* After cloning, the original response's body will be consumed and closed.
*
* @see https://github.com/vercel/next.js/pull/73274
*
* @param original - The original response to clone.
* @returns A tuple containing two independent clones of the original response.
*/
export function cloneResponse(original: Response): [Response, Response] {
// If the response has no body, then we can just return the original response
// twice because it's immutable.
if (!original.body) {
return [original, original]
}
const [body1, body2] = original.body.tee()
const cloned1 = new Response(body1, {
status: original.status,
statusText: original.statusText,
headers: original.headers,
})
Object.defineProperty(cloned1, 'url', {
value: original.url,
// How the original response.url behaves
configurable: true,
enumerable: true,
writable: false,
})
// The Fetch Standard allows users to skip consuming the response body by
// relying on garbage collection to release connection resources.
// https://github.com/nodejs/undici?tab=readme-ov-file#garbage-collection
//
// To cancel the stream you then need to cancel both resulting branches.
// Teeing a stream will generally lock it for the duration, preventing other
// readers from locking it.
// https://developer.mozilla.org/en-US/docs/Web/API/ReadableStream/tee
// cloned2 is stored in a react cache and cloned for subsequent requests.
// It is the original request, and is is garbage collected by a
// FinalizationRegistry in Undici, but since we're tee-ing the stream
// ourselves, we need to cancel clone1's stream (the response returned from
// our dedupe fetch) when clone1 is reclaimed, otherwise we leak memory.
if (registry && cloned1.body) {
registry.register(cloned1, new WeakRef(cloned1.body))
}
const cloned2 = new Response(body2, {
status: original.status,
statusText: original.statusText,
headers: original.headers,
})
Object.defineProperty(cloned2, 'url', {
value: original.url,
// How the original response.url behaves
configurable: true,
enumerable: true,
writable: false,
})
return [cloned1, cloned2]
}
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