[Emitter] Wrong design:type metadata for decorated fields

[pcan]

When I compile this code:

class A {
    constructor() { console.log('new A'); }
}

type AType = A;

function decorator(target: Object, propertyKey: string) {
}

export class B {

    @decorator
    x: AType = new A();
}

The emitter produces the following code:

var A = (function () {
    function A() {
        console.log('new A');
    }
    return A;
})();
function decorator(target, propertyKey) {
}
var B = (function () {
    function B() {
        this.x = new A();
    }
    __decorate([
        decorator, 
        __metadata('design:type', Object)
    ], B.prototype, "x");
    return B;
})();
exports.B = B;

But the expected output for metadata should be __metadata('design:type', A). Furthermore, if I change the param declaration to x: A = new A();, the emitter will output __metadata('design:type', ) (type not specified at all).

[fopsdev]

i think i'm running into the same issue here:

import {bindable} from 'aurelia-framework';

export class NavBar {
  @bindable router = null ;
}

gets translated to:

...
        __decorate([
            aurelia_framework_1.bindable, 
            __metadata('design:type', )
...

[mhegazy]

This is by design. the intended behavior is not doable for the general case. one thing to keep in mind is we are serializing the type using the constructor function. if you alias it, the constructor function might not be, and probably is not, in scope.

consider this:

// a.ts
class A {
}

export type TypeA = A;
export function getA() {  return new A(); } 

and

// b.ts
import {AType, getA} from "a";
export class B {
    @decorator
    x: AType = getA(); // 'A' is not in scope here, the value will be undefined.
}

Solutions, either you use import aliasForA = A, which will generate a variable aliasForA = A so the serialization would work, or not use type aliases.

[mhegazy]

@fopsdev this is a different issue. i will file a different bug to track it

[wwwsevolod]

@mhegazy what about @fopsdev issue? can't find created bug ;( im stuck with this bug too =
but little bit different:

class TestAction extends ActionCreator {
    dispatch(a: number) {
        return a;
    }
}

function InjectAction(target: any, a: any) {
    console.log(target);
    console.log(typeof a);
    // Reflect.getMetadata('design:type', target)
}

class Test extends Component<any, any> {
    @InjectAction
    testAction: TestAction;

    render() {
        return <div>
            123
        </div>;
    }
}

produces

   40 | __decorate([
   41 |     InjectAction, 
> 42 |     __metadata('design:type', )
    |                               ^
   43 | ], Test.prototype, "testAction");