@jspm/generator/lib/common/fetch.js

Package Import Map Generation Tool

// @ts-ignore
import { fetch as fetchImpl, clearCache } from '#fetch';
let retryCount = 5, poolSize = 100;
export function setRetryCount(count) {
    retryCount = count;
}
export function setFetchPoolSize(size) {
    poolSize = size;
}
/**
 * Allows customizing the fetch implementation used by the generator.
 */ export function setFetch(fetch) {
    _fetch = wrappedFetch(fetch);
}
const virtualSources = {};
/**
 * Allows virtual sources to be defined into the wrapped fetch implementation.
 */ export function setVirtualSourceData(urlBase, sourceData) {
    virtualSources[urlBase.endsWith('/') ? urlBase : urlBase + '/'] = sourceData;
}
const emptyHeaders = new Headers();
const jsonHeaders = new Headers([
    [
        'content-type',
        'application/json'
    ]
]);
function sourceResponse(url, buffer) {
    return {
        url,
        ok: true,
        headers: url.endsWith('.json') ? jsonHeaders : emptyHeaders,
        status: 200,
        async text () {
            return buffer.toString();
        },
        async json () {
            return JSON.parse(buffer.toString());
        },
        arrayBuffer () {
            if (typeof buffer === 'string') return new TextEncoder().encode(buffer.toString()).buffer;
            return new Uint8Array(buffer);
        }
    };
}
/**
 * Wraps a fetch request with pooling, retry logic on exceptions (emfile / network errors),
 * and source virtualization.
 */ function wrappedFetch(fetch) {
    const wrappedFetch = async function(url, ...args) {
        url = url.toString();
        let matchedVirtual = false;
        for (const virtualBase of Object.keys(virtualSources)){
            if (url.startsWith(virtualBase)) {
                const virtualFileData = virtualSources[virtualBase];
                let subdir = url.slice(virtualBase.length);
                const source = virtualFileData[subdir];
                if (source) return sourceResponse(url, source);
                // check if we have files within this virtual source path as a folder
                // and if so return the file listing as a 204 listing (internal non-public convention)
                let dirFiles = null;
                if (!subdir.endsWith('/') && subdir.length) subdir += '/';
                for (const file of Object.keys(virtualFileData)){
                    if (file.startsWith(subdir)) {
                        dirFiles = dirFiles || [];
                        let filename = file.slice(subdir.length);
                        if (filename.indexOf('/') !== -1) {
                            filename = filename.slice(0, filename.indexOf('/'));
                            if (dirFiles.includes(filename)) continue;
                        }
                        dirFiles.push(filename);
                    }
                }
                if (dirFiles) {
                    return {
                        // we use a 204 status for directory responses on the filesystem
                        // which support listing. This is only a local internal convention,
                        // not intended for external URLs.
                        ok: true,
                        status: 204,
                        headers: emptyHeaders,
                        async text () {
                            return '';
                        },
                        async json () {
                            return dirFiles;
                        },
                        arrayBuffer () {
                            return new ArrayBuffer(0);
                        }
                    };
                }
                // we allow fallthrough to other virtual source bases
                // that is, virtual source bases are allowed to nest eachother
                // this may not be useful in which case we can remove
                matchedVirtual = true;
            }
        }
        if (matchedVirtual) {
            return {
                url,
                ok: false,
                headers: emptyHeaders,
                status: 404,
                statusText: 'Virtual source not found'
            };
        }
        let retries = 0;
        try {
            await pushFetchPool();
            while(true){
                try {
                    return await fetch(url, ...args);
                } catch (e) {
                    if (retries++ >= retryCount) throw e;
                }
            }
        } finally{
            popFetchPool();
        }
    };
    return wrappedFetch;
}
// restrict in-flight fetches to a pool of 100
let p = [];
let c = 0;
function pushFetchPool() {
    if (++c > poolSize) return new Promise((r)=>p.push(r));
}
function popFetchPool() {
    c--;
    if (p.length) p.shift()();
}
let _fetch = wrappedFetch(fetchImpl);
export { clearCache, _fetch as fetch };


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