some suggestions about emitDecoratorMetadata

[berbar]

TypeScript Version: 3.7.0-dev.20191009

Search Terms:

It sets that 'emitDecoratorMetadata' is true in the 'tsconfig.json'.

If the classes depend on one another, It will occur exception.

Code

function TestReflect()
{
    return function( target: any, methodName?: string ): any
    {
    }
}

class Apple
{
    // Need Banana
    @TestReflect()
    public Some( banana: Banana )
    {
    }
}

@TestReflect()
class Banana
{
    // Need Apple
    public constructor( apple: Apple )
    {
    }
}

Expected behavior:

function TestReflect() {
    return function (target, methodName) {
    };
}
class Apple {
    Some(banana) {
    }
}
__decorate([
    TestReflect(),
    __metadata("design:type", Function),
    // __metadata("design:paramtypes", [Banana]),

    // i wish there is another new option to emit metadata like this
    // add a function '()=>Banana' into metadata
    __metadata("design:paramtypes:delay", [ ()=>Banana ] ),
    // or this
    // with more type informations
    __metadata("design:paramtypes:new", [ { GenericTypeDefinition: ()=>Banana, GenericArguments: [ () => Number ] }]),

    __metadata("design:returntype", void 0)
], Apple.prototype, "Some", null);
let Banana = class Banana {
    constructor(apple) {
    }
};
Banana = __decorate([
    TestReflect(),
    __metadata("design:paramtypes", [Apple])
], Banana);

Actual behavior:

function TestReflect() {
    return function (target, methodName) {
    };
}
class Apple {
    Some(banana) {
    }
}
__decorate([
    TestReflect(),
    __metadata("design:type", Function),
    // it will occur exception here.
    // Uncaught ReferenceError: Banana is not defined.
    __metadata("design:paramtypes", [Banana]),
    __metadata("design:returntype", void 0)
], Apple.prototype, "Some", null);
let Banana = class Banana {
    constructor(apple) {
    }
};
Banana = __decorate([
    TestReflect(),
    __metadata("design:paramtypes", [Apple])
], Banana);

Playground Link:

Related Issues:

[berbar]

    // option to emit the name of parameters
    __metadata("design:paramnames", [ "banana" ] ),

[MartinJohns]

Looks like a duplicate of #27519.

And quoting @mhegazy:

The meta-data emit, continues to be an experimental feature tied to decorators, and has a very limited scope (i.e. classes and primitives). we have no plans to expand that scope either.

[typescript-bot]

This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.