Legacy Decorators

Goal

Create a legacy method decorator using the unified context style.

Implementation

import { Methods } from '@litert/decorator/legacy';

function track(label: string): Methods.ICallbackFn {

    return Methods.create((ctx) => {
        Reflect.defineProperty(ctx.constructor, label, {
            configurable: true,
            value: ctx.name,
        });
    });
}

class Service {

    @track('trackedMethod')
    public run(): void {}
}

Metadata

Legacy decorators should use the reflect-metadata module to store and read metadata. Do not use getMetadataContainer — that API is designed for modern (Stage 3) decorators only.

import 'reflect-metadata';
import { Methods } from '@litert/decorator/legacy';

function mark(name: string): Methods.ICallbackFn {

    return Methods.create((ctx) => {
        Reflect.defineMetadata(name, true, ctx.constructor);
    });
}

class Service {

    @mark('tracked')
    public run(): void {}
}

console.log(Reflect.getMetadata('tracked', Service)); // true

Example code

Decorator kind	Example
Class	Class.ts
Method	Method.ts
Property	Property.ts
Accessor	Accessor.ts
Getter	Getter.ts
Setter	Setter.ts
Static method	StaticMethod.ts
Static property	StaticProperty.ts
Static accessor	StaticAccessor.ts
Static getter	StaticGetter.ts
Static setter	StaticSetter.ts
Method parameter	MethodParameter.ts
Static method parameter	StaticMethodParameter.ts
Constructor parameter	ConstructorParameter.ts

Notes

Step	Reason
Use Methods.create	The callback receives one normalized context object instead of raw legacy decorator arguments.
Read ctx.constructor	The unified context always includes the decorated class constructor.
Read ctx.descriptor when available	Method, accessor, getter, and setter decorators expose their property descriptor through the context.