Stage 3 Decorators not applying defineProperty

[augustsaintfreytag]

Deno 2.2.6
Node 23.6.1

Description

Defining a Stage 3 class property decorator that mutates its class property from data field to a getter/setter field seems to silently fail to mutate the type. The mutation the decorator does is effectively an Object.defineProperty(this, name, {…}) call. The get and set blocks are never called on the instance and inspecting the instance’s getOwnPropertyDescriptor also confirms that no get or set exists on the type.

When running the code with deno run file.ts, the decorator is effectively not applied at all. Compiling the exact same code with tsc and running it with node file.js works as expected.

Preview

export function InstanceProperty() {
	return function (_value: unknown, context: ClassFieldDecoratorContext) {
		const { name } = context
		const dataPropertyName = `__${String(name)}`

		return function (this: any, initialValue: unknown) {
			this[dataPropertyName] = initialValue

			Object.defineProperty(this, name, {
				get() {
					console.log(`Reading and returning value for property ${String(name)}, ${this[dataPropertyName]}`)
					return this[dataPropertyName]
				},
				set(newValue) {
					console.log(`Setting value for property ${String(name)} to ${newValue}`)
					this[dataPropertyName] = newValue
				},
				enumerable: true,
				configurable: true
			})

			return undefined
		}
	}
}

Reproduction

Here’s a reproduction: https://github.com/augustsaintfreytag/repro-deno-decorators