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// Shared utilities for speculation measurement tests.
function isSpeculationMeasurementEnabled() {
return typeof performance.getSpeculations === 'function';
}
// Static support files for each "as" type, keyed by a unique suffix to allow
// multiple preloads of the same type in one test page without cache collisions.
function supportFileUrl(as, suffix = '') {
const files = {
'script': 'support/preloaded-script.js',
'style': 'support/preloaded-style.css',
'fetch': 'support/preloaded-data.txt',
};
const base = files[as];
if (!base) throw new Error(`No support file for as="${as}"`);
// Append a cache-busting query to avoid collisions between tests.
return new URL(`${base}?v=${suffix || crypto.randomUUID()}`,
location.href).href;
}
// Add a <link rel=preload> and wait for it to finish loading.
// Returns {link, href} once the preload fires onload/onerror.
//
// Options:
// t: test object (for cleanup)
// as: the "as" attribute value (default: "script")
// crossorigin: the crossorigin attribute value, or null for none
// href: explicit URL (auto-generated from support files if omitted)
async function addPreloadAndWait({t, as = 'script', crossorigin = null,
href = null} = {}) {
if (!href) {
href = supportFileUrl(as);
}
const link = document.createElement('link');
link.rel = 'preload';
link.as = as;
link.href = href;
if (crossorigin !== null) {
link.crossOrigin = crossorigin;
}
const loaded = new Promise((resolve, reject) => {
link.onload = resolve;
link.onerror = resolve; // still tracked even on error
});
document.head.appendChild(link);
t.add_cleanup(() => link.remove());
await loaded;
return {link, href: link.href};
}
// Use a previously-preloaded resource by inserting the appropriate element.
// Returns a promise that resolves when the resource is loaded.
async function usePreload({t, as, href, crossorigin = null} = {}) {
let el;
if (as === 'script') {
el = document.createElement('script');
el.src = href;
if (crossorigin !== null) {
el.crossOrigin = crossorigin;
}
} else if (as === 'style') {
el = document.createElement('link');
el.rel = 'stylesheet';
el.href = href;
if (crossorigin !== null) {
el.crossOrigin = crossorigin;
}
} else if (as === 'fetch') {
// For fetch-type preloads, use fetch() API to consume.
const opts = {};
if (crossorigin === 'anonymous') {
opts.mode = 'cors';
opts.credentials = 'same-origin';
} else if (crossorigin === 'use-credentials') {
opts.mode = 'cors';
opts.credentials = 'include';
}
await fetch(href, opts);
return; // no element to clean up
} else {
throw new Error(`usePreload does not support as="${as}" yet`);
}
const loaded = new Promise((resolve, reject) => {
el.onload = resolve;
el.onerror = resolve; // still counts as "used" even on error
});
document.body.appendChild(el);
t.add_cleanup(() => el.remove());
await loaded;
}
// Find a PreloadData entry whose URL contains the given substring.
function findPreloadByUrl(preloads, urlSubstring) {
return preloads.find(p => p.url.includes(urlSubstring));
}
// Map crossorigin attribute value to expected CrossOriginMode enum string.
function expectedCrossOriginMode(crossorigin) {
if (crossorigin === null || crossorigin === undefined) return 'none';
if (crossorigin === '' || crossorigin === 'anonymous') return 'anonymous';
if (crossorigin === 'use-credentials') return 'use-credentials';
return 'none';
}