Module not imported for meta-data references.

[mhegazy]

From #12888 (comment)

after upgrading to TypeScript 2.1.5.
the issue regressed in different place.

when 'strictNullCheck' option is false the following typescript emitt invalid javascript code.

file: auxiliry.ts

export class SomeClass {
    field: string;
}

file: main.ts

import { SomeClass } from './auxiliry';

function annotation(): PropertyDecorator {
    return (target: any): void => { };
}

export class ClassA {
    @annotation() array: SomeClass | null;
}

Emitted code:

"use strict";
var __decorate = (this && this.__decorate) || function (decorators, target, key, desc) {
    var c = arguments.length, r = c < 3 ? target : desc === null ? desc = Object.getOwnPropertyDescriptor(target, key) : desc, d;
    if (typeof Reflect === "object" && typeof Reflect.decorate === "function") r = Reflect.decorate(decorators, target, key, desc);
    else for (var i = decorators.length - 1; i >= 0; i--) if (d = decorators[i]) r = (c < 3 ? d(r) : c > 3 ? d(target, key, r) : d(target, key)) || r;
    return c > 3 && r && Object.defineProperty(target, key, r), r;
};
var __metadata = (this && this.__metadata) || function (k, v) {
    if (typeof Reflect === "object" && typeof Reflect.metadata === "function") return Reflect.metadata(k, v);
};
function annotation() {
    return function (target) { };
}
var ClassA = (function () {
    function ClassA() {
    }
    return ClassA;
}());
__decorate([
    annotation(),
    __metadata("design:type", auxiliry_1.SomeClass) // <-- auxiliry_1 is not emitted as require statement
], ClassA.prototype, "array", void 0);
exports.ClassA = ClassA;

[larrifax]

I'm having the same problem with strictNullChecks turned on.

@Input() employee: Employee | undefined; // This crashes at runtime
@Input() employee?: Employee; // Workaround

@Input() set employee(value: Employee | undefined) { // This crashes at runtime
    ...
}
@Input() set employee(value?: Employee) { // Compiler error
    ...
}

I can work around the problem on regular fields (line 1 & 2), but the workaround isn't applicable for properties as they don't allow optional parameters.

Will there be a bugfix for this in 2.2, or do I have to wait for 2.3? I'm currently stuck at 2.1 because of this problem.

[evmar]

Just wanted to note we have more than ten instances of this bug coming up within Google in various user code, which means we are needing to teach our users to sprinkle

const workaround = Import;

in their code to make some Import symbol not get dropped.

[studds]

When will this be released?