next/dist/esm/server/lib/dedupe-fetch.js

The React Framework

/**
 * Based on https://github.com/facebook/react/blob/d4e78c42a94be027b4dc7ed2659a5fddfbf9bd4e/packages/react/src/ReactFetch.js
 */ import * as React from 'react';
import { cloneResponse } from './clone-response';
import { InvariantError } from '../../shared/lib/invariant-error';
const simpleCacheKey = '["GET",[],null,"follow",null,null,null,null]' // generateCacheKey(new Request('https://blank'));
;
function generateCacheKey(request) {
    // We pick the fields that goes into the key used to dedupe requests.
    // We don't include the `cache` field, because we end up using whatever
    // caching resulted from the first request.
    // Notably we currently don't consider non-standard (or future) options.
    // This might not be safe. TODO: warn for non-standard extensions differing.
    // IF YOU CHANGE THIS UPDATE THE simpleCacheKey ABOVE.
    return JSON.stringify([
        request.method,
        Array.from(request.headers.entries()),
        request.mode,
        request.redirect,
        request.credentials,
        request.referrer,
        request.referrerPolicy,
        request.integrity
    ]);
}
export function createDedupeFetch(originalFetch) {
    const getCacheEntries = React.cache(// eslint-disable-next-line @typescript-eslint/no-unused-vars -- url is the cache key
    (url)=>[]);
    return function dedupeFetch(resource, options) {
        if (options && options.signal) {
            // If we're passed a signal, then we assume that
            // someone else controls the lifetime of this object and opts out of
            // caching. It's effectively the opt-out mechanism.
            // Ideally we should be able to check this on the Request but
            // it always gets initialized with its own signal so we don't
            // know if it's supposed to override - unless we also override the
            // Request constructor.
            return originalFetch(resource, options);
        }
        // Normalize the Request
        let url;
        let cacheKey;
        if (typeof resource === 'string' && !options) {
            // Fast path.
            cacheKey = simpleCacheKey;
            url = resource;
        } else {
            // Normalize the request.
            // if resource is not a string or a URL (its an instance of Request)
            // then do not instantiate a new Request but instead
            // reuse the request as to not disturb the body in the event it's a ReadableStream.
            const request = typeof resource === 'string' || resource instanceof URL ? new Request(resource, options) : resource;
            if (request.method !== 'GET' && request.method !== 'HEAD' || request.keepalive) {
                // We currently don't dedupe requests that might have side-effects. Those
                // have to be explicitly cached. We assume that the request doesn't have a
                // body if it's GET or HEAD.
                // keepalive gets treated the same as if you passed a custom cache signal.
                return originalFetch(resource, options);
            }
            cacheKey = generateCacheKey(request);
            url = request.url;
        }
        const cacheEntries = getCacheEntries(url);
        for(let i = 0, j = cacheEntries.length; i < j; i += 1){
            const [key, promise] = cacheEntries[i];
            if (key === cacheKey) {
                return promise.then(()=>{
                    const response = cacheEntries[i][2];
                    if (!response) throw Object.defineProperty(new InvariantError('No cached response'), "__NEXT_ERROR_CODE", {
                        value: "E579",
                        enumerable: false,
                        configurable: true
                    });
                    // We're cloning the response using this utility because there exists
                    // a bug in the undici library around response cloning. See the
                    // following pull request for more details:
                    // https://github.com/vercel/next.js/pull/73274
                    const [cloned1, cloned2] = cloneResponse(response);
                    cacheEntries[i][2] = cloned2;
                    return cloned1;
                });
            }
        }
        // We pass the original arguments here in case normalizing the Request
        // doesn't include all the options in this environment.
        const promise = originalFetch(resource, options);
        const entry = [
            cacheKey,
            promise,
            null
        ];
        cacheEntries.push(entry);
        return promise.then((response)=>{
            // We're cloning the response using this utility because there exists
            // a bug in the undici library around response cloning. See the
            // following pull request for more details:
            // https://github.com/vercel/next.js/pull/73274
            const [cloned1, cloned2] = cloneResponse(response);
            entry[2] = cloned2;
            return cloned1;
        });
    };
}

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