tc39-weakrefs-shim/module/index.js

Shim for TC39 Weakrefs proposal

import globalAvailable from "./global/available.js";
import nodeAvailable from "./node/available.js";
import spidermonkeyAvailable from "./spidermonkey/available.js";
function testKnownImplementationIssues(WeakRef, FinalizationGroup) {
    try {
        const finalizationGroup = new FinalizationGroup(() => { });
        if (finalizationGroup.unregister({}) !== false)
            return false;
        try {
            finalizationGroup.cleanupSome({});
            return false;
        }
        catch (err) { }
    }
    catch (err) {
        return false;
    }
    return true;
}
export const available = globalAvailable || spidermonkeyAvailable || nodeAvailable;
export async function shim(wrapBrokenImplementation = true) {
    let implementation;
    if (globalAvailable) {
        implementation = await import("./global/index.js");
        if (wrapBrokenImplementation &&
            !testKnownImplementationIssues(implementation.WeakRef, implementation.FinalizationGroup)) {
            implementation = (await import("./wrapper.js")).wrap(implementation.WeakRef, implementation.FinalizationGroup, implementation.gc);
        }
    }
    else if (spidermonkeyAvailable) {
        implementation = await import("./spidermonkey/index.js");
    }
    else if (nodeAvailable) {
        implementation = await import("./node/index.js");
    }
    else {
        implementation = { WeakRef: undefined, FinalizationGroup: undefined };
    }
    return implementation;
}
let asyncImportPromise;
// Easy use of the shim with dynamic import
export function then(onfulfilled, onrejected) {
    if (!asyncImportPromise)
        asyncImportPromise = shim().then(exports => ({
            shim,
            available,
            ...exports,
        }));
    return asyncImportPromise.then(onfulfilled, onrejected);
}
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