/** * We extend `Date` during builds and revalidates to ensure that prerenders don't observe the clock as a source of IO * When cacheComponents is enabled. The current time is a form of IO even though it resolves synchronously. When cacheComponents is * enabled we need to ensure that clock time is excluded from prerenders unless it is cached. * * There is tension here because time is used for both output and introspection. While arbitrary we intend to reserve * `Date` for output use cases and `performance` for introspection use cases. If you want to measure * how long something takes use `performance.timeOrigin` and `performance.now()` rather than `Date.now()` for instance. * * The extensions here never error nor alter the underlying Date objects, strings, and numbers created and thus should be transparent to callers. */ import { io } from './utils' function createNow(originalNow: typeof Date.now) { return { now: function now() { io('`Date.now()`', 'time') return originalNow() }, }['now'.slice() as 'now'].bind(null) } function createDate(originalConstructor: typeof Date): typeof Date { const properties = Object.getOwnPropertyDescriptors(originalConstructor) properties.now.value = createNow(originalConstructor.now) const apply = Reflect.apply const construct = Reflect.construct const newConstructor = Object.defineProperties( // Ideally this should not minify the name. function Date() { if (new.target === undefined) { io('`Date()`', 'time') return apply(originalConstructor, undefined, arguments) } if (arguments.length === 0) { io('`new Date()`', 'time') } return construct(originalConstructor, arguments, new.target) }, properties ) Object.defineProperty(originalConstructor.prototype, 'constructor', { value: newConstructor, }) return newConstructor as typeof Date } try { // eslint-disable-next-line no-native-reassign Date = createDate(Date) } catch { console.error( 'Failed to install `Date` class extension. When using `experimental.cacheComponents`, APIs that read the current time will not correctly trigger dynamic behavior.' ) }