Allow non-global helper functions

[vladima]

Original issue: systemjs/builder#178

[pkozlowski-opensource]

@vladima is this issue is going to cover having some kind of runtime file with all the helpers? Currently using the noEmitHelpers: true flag will remove emitting helpers (like __decorate, __metadata etc.) from individual files. Still it would be great to have a file (as part of the TS npm distribution) that includes all those helpers.

Currently I'm hand-crafting this file on my end by moving generated helpers functions to one file checked-in in my project repo. Is there is a better way of doing this today? Or is it going to be covered by this issue?

[mhegazy]

Is this issue still needed?

[daniel-a-melo]

If helpers functions are emitted right before a System.register call it prevents this module from being loaded from SystemJS. As it seems to be a valid use case it would be nice to have some config option to prevent that

[mhegazy]

the helpers emit have been moved in 1.6 to inside the System.register call. so

export class B {}
export class C extends B {}

emits:

System.register([], function(exports_1) {
    var __extends = (this && this.__extends) || function (d, b) {
        for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
        function __() { this.constructor = d; }
        d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
    };
    var B, C;
    return {
        setters:[],
        execute: function() {
            B = (function () {
                function B() {
                }
                return B;
            })();
            exports_1("B", B);
            C = (function (_super) {
                __extends(C, _super);
                function C() {
                    _super.apply(this, arguments);
                }
                return C;
            })(B);
            exports_1("C", C);
        }
    }
});

[mhegazy]

I chatted with @vladima offline, this issue is tracking moving the helpers into a module, and alloing the compiler to emit imports to that module, e.g. the above code would emit:

System.register(["ts_helpers"], function(exports_1) {
    var __extends;
    var B, C;
    return {
        setters:[function(ts_helpers) {
            __extends = ts_helpers.__extends;
        }],
        execute: function() {
            B = (function () {
                function B() {
                }
                return B;
            })();
            exports_1("B", B);
            C = (function (_super) {
                __extends(C, _super);
                function C() {
                    _super.apply(this, arguments);
                }
                return C;
            })(B);
            exports_1("C", C);
        }
    }
});