Improve proxyLazy
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@ -16,9 +16,46 @@
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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import { makeLazy } from "./misc";
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// Proxies demand that these properties be unmodified, so proxyLazy
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// will always return the function default for them.
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const unconfigurable = ["arguments", "caller", "prototype"];
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const ProxyDummy = function () { };
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const handler: ProxyHandler<any> = {};
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for (const method of [
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"apply",
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"construct",
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"defineProperty",
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"deleteProperty",
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"get",
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"getOwnPropertyDescriptor",
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"getPrototypeOf",
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"has",
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"isExtensible",
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"ownKeys",
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"preventExtensions",
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"set",
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"setPrototypeOf"
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]) {
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handler[method] =
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(target: any, ...args: any[]) => Reflect[method](target.get(), ...args);
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}
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handler.ownKeys = target => {
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const v = target.get();
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const keys = Reflect.ownKeys(v);
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for (const key of unconfigurable) {
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if (!keys.includes(key)) keys.push(key);
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}
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return keys;
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};
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handler.getOwnPropertyDescriptor = (target, p) => {
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if (typeof p === "string" && unconfigurable.includes(p))
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return Reflect.getOwnPropertyDescriptor(target, p);
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return Reflect.getOwnPropertyDescriptor(target.get(), p);
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};
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/**
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* Wraps the result of {@see makeLazy} in a Proxy you can consume as if it wasn't lazy.
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@ -30,17 +67,10 @@ const ProxyDummy = function () { };
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* @example const mod = proxyLazy(() => findByProps("blah")); console.log(mod.blah);
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*/
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export function proxyLazy<T>(factory: () => T): T {
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const lazy = makeLazy(factory);
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const proxyDummy: { (): void; cachedValue?: T; get(): T; } = function () { };
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return new Proxy(ProxyDummy, {
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get: (_, prop) => lazy()[prop],
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set: (_, prop, value) => lazy()[prop] = value,
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has: (_, prop) => prop in lazy(),
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apply: (_, $this, args) => (lazy() as Function).apply($this, args),
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ownKeys: () => Reflect.ownKeys(lazy() as object),
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construct: (_, args) => Reflect.construct(lazy() as Function, args),
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deleteProperty: (_, prop) => delete lazy()[prop],
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defineProperty: (_, property, attributes) => !!Object.defineProperty(lazy(), property, attributes),
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getPrototypeOf: () => Object.getPrototypeOf(lazy())
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}) as any as T;
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proxyDummy.cachedValue = void 0;
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proxyDummy.get = () => proxyDummy.cachedValue ??= factory();
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return new Proxy(proxyDummy, handler) as any;
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}
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