Runtime parameter info (name, optional, default)

TypeScript Version:

1.8.9

Code

I'm trying to leverage decorators to create runtime contracts to check against incoming parameters.

Below is the ts code

class Foo {

  @contract
  test (a : integer, b : string) : boolean {
    return true
  }

  @contract
  testOptional (a : integer, b? : string) : boolean {
    return true
  }

  @contract
  testDefault (a : integer, b : string = 'hello') : boolean {
    return true
  }
}

The above generated the following Javascript.

var Foo = (function () {
    function Foo() {
    }
    Foo.prototype.test = function (a, b) {
        return true;
    };
    Foo.prototype.testOptional = function (a, b) {
        return true;
    };
    Foo.prototype.testDefault = function (a, b) {
        if (b === void 0) { b = 'hello'; }
        return true;
    };
    __decorate([
        contract, 
        __metadata('design:type', Function), 
        __metadata('design:paramtypes', [integer, String]), 
        __metadata('design:returntype', Boolean)
    ], Foo.prototype, "test", null);
    __decorate([
        contract, 
        __metadata('design:type', Function), 
        __metadata('design:paramtypes', [integer, String]), // same as above
        __metadata('design:returntype', Boolean)
    ], Foo.prototype, "testOptional", null);
    __decorate([
        contract, 
        __metadata('design:type', Function), 
        __metadata('design:paramtypes', [integer, String]), // same as above
        __metadata('design:returntype', Boolean)
    ], Foo.prototype, "testDefault", null);
    return Foo;
}());

Note that the three different ts functions generated the exact sets of __metadata calls. The design:paramtypes alone cannot distinguish whether a particular parameter is optional or has default values, and thus insufficient for building a runtime contract.

It would be great for TypeScript to support a full parameter info so decorators can be made more capable.

Inizia dall’emissione dei metadati dei decorator mostrata nel JavaScript generato, in particolare dalle chiamate a design:paramtypes e __metadata. Confronta i metadati prodotti per test, testOptional e testDefault. Il lavoro è completato quando i decorator a runtime possono distinguere i nomi dei parametri, i parametri opzionali e i valori predefiniti, e il comportamento rilevante è coperto dai test.