// ==UserScript==
// @name        gh_2215_make_GM_xhr_more_parallel_again
// @namespace   https://github.com/Tampermonkey/tampermonkey/issues/2215
// @version     1.0
// @description Go to https://github.com/Tampermonkey/tampermonkey/issues/2215 for more.
// @author      Tampermonkey
// ==/UserScript==
/*
* https://github.com/Tampermonkey/tampermonkey/issues/2215
*
* This script provides a workaround for a Chrome MV3 issue (https://github.com/w3c/webextensions/issues/694)
* where extensions can't set/delete headers that are preserved over redirects.
*
* By setting `redirect: 'manual'` and following redirects manually, this script ensures request redirects work
* as intended and requests to different URLs are made in parallel (again).
*
* Userscript authors should include this as a `@require` when they need to make parallel requests with GM_xmlhttpRequest,
* especially if requests might take a long time to complete.
*
* Including this script will modify the behavior of GM_xmlhttpRequest and GM.xmlHttpRequest in Tampermonkey only.
*
* Usage:
*
* Add this to the metadata block of your userscript:
*
* // @grant     GM_xmlhttpRequest
* // @require   https://raw.githubusercontent.com/Tampermonkey/utils/refs/heads/main/requires/gh_2215_make_GM_xhr_more_parallel_again.js
*
**/
/* global GM_info, GM_xmlhttpRequest, GM */
const HAS_GM = typeof GM !== 'undefined';
const NEW_GM = ((scope, GM) => {
// Check if running in Tampermonkey and if version supports redirect control
if (GM_info.scriptHandler !== "Tampermonkey" || compareVersions(GM_info.version, "5.3.2") < 0) return;
// Backup original functions
const GM_xmlhttpRequestOrig = GM_xmlhttpRequest;
const GM_xmlHttpRequestOrig = GM.xmlHttpRequest;
function compareVersions(v1, v2) {
const parts1 = v1.split('.').map(Number);
const parts2 = v2.split('.').map(Number);
const length = Math.max(parts1.length, parts2.length);
for (let i = 0; i < length; i++) {
const num1 = parts1[i] || 0;
const num2 = parts2[i] || 0;
if (num1 > num2) return 1;
if (num1 < num2) return -1;
}
return 0;
}
// Wrapper for GM_xmlhttpRequest
function GM_xmlhttpRequestWrapper(odetails) {
// If redirect is manually set, simply pass odetails to the original function
if (odetails.redirect !== undefined) {
return GM_xmlhttpRequestOrig(odetails);
}
// Warn if onprogress is used with settings incompatible with fetch mode used in background
if (odetails.onprogress || odetails.fetch === false) {
console.warn("Fetch mode does not support onprogress in the background.");
}
const {
onload,
onloadend,
onerror,
onabort,
ontimeout,
...details
} = odetails;
// Set redirect to manual and handle redirects
const handleRedirects = (initialDetails) => {
const request = GM_xmlhttpRequestOrig({
...initialDetails,
redirect: 'manual',
onload: function(response) {
if (response.status >= 300 && response.status < 400) {
const m = response.responseHeaders.match(/Location:\s*(\S+)/i);
// Follow redirect manually
const redirectUrl = m && m[1];
if (redirectUrl) {
const absoluteUrl = new URL(redirectUrl, initialDetails.url).href;
handleRedirects({ ...initialDetails, url: absoluteUrl });
return;
}
}
if (onload) onload.call(this, response);
if (onloadend) onloadend.call(this, response);
},
onerror: function(response) {
if (onerror) onerror.call(this, response);
if (onloadend) onloadend.call(this, response);
},
onabort: function(response) {
if (onabort) onabort.call(this, response);
if (onloadend) onloadend.call(this, response);
},
ontimeout: function(response) {
if (ontimeout) ontimeout.call(this, response);
if (onloadend) onloadend.call(this, response);
}
});
return request;
};
return handleRedirects(details);
}
// Wrapper for GM.xmlHttpRequest
function GM_xmlHttpRequestWrapper(odetails) {
let abort;
const p = new Promise((resolve, reject) => {
const { onload, ontimeout, onerror, ...send } = odetails;
send.onerror = function(r) {
if (onerror) {
resolve(r);
onerror.call(this, r);
} else {
reject(r);
}
};
send.ontimeout = function(r) {
if (ontimeout) {
// See comment above
resolve(r);
ontimeout.call(this, r);
} else {
reject(r);
}
};
send.onload = function(r) {
resolve(r);
if (onload) onload.call(this, r);
};
const a = GM_xmlhttpRequestWrapper(send).abort;
if (abort === true) {
a();
} else {
abort = a;
}
});
p.abort =  () => {
if (typeof abort === 'function') {
abort();
} else {
abort = true;
}
};
return p;
}
// Export wrappers
GM_xmlhttpRequest = GM_xmlhttpRequestWrapper;
scope.GM_xmlhttpRequestOrig = GM_xmlhttpRequestOrig;
const gopd = Object.getOwnPropertyDescriptor(GM, 'xmlHttpRequest');
if (gopd && gopd.configurable === false) {
return {
__proto__: GM,
xmlHttpRequest: GM_xmlHttpRequestWrapper,
xmlHttpRequestOrig: GM_xmlHttpRequestOrig
};
} else {
GM.xmlHttpRequest = GM_xmlHttpRequestWrapper;
GM.xmlHttpRequestOrig = GM_xmlHttpRequestOrig;
}
})(this, HAS_GM ? GM : {});
if (HAS_GM && NEW_GM) GM = NEW_GM;