When using a custom decorator on a get accessor, why do I get an error about an 'Invalid property descriptor'?

Issue

For some reason when I use a decorator on a get accessor (as shown below), I pass compilation, but always end up with a runtime error message saying:

Uncaught TypeError: Invalid property descriptor. Cannot both specify accessors and a value or writable attribute

Why does this happen and how can I overcome it? To note: I am only using a getter and not a setter.

Example Code:

class ThingBox {
    private things = [1,2,3,4,5]

    @MyDecorator
    get totalTings(): number { return this.things.length }
}

Playground Link Example

Solution

You have set a get method and value in the descriptor, but this is invalid (you can have accessors or value, not both). In your case, you need to patch the get method inside of the decorator instead of value.

Answered By - izmaylovdev