Emitted decorator metadata is different when --isolatedModules is set

[jpsfs]

Hi,

I'm facing an issue while compiling an Angular 2 application with the IsolatedModules flag set to true.
If IsolatedModules is set to false everything works as expect.

The emitted decorator metadata is different. Is this by design or a bug?

My problem is that my module is getting bigger by the day and using this flag I can greatly improve the CompileOnSave experience.

TypeScript Version:

1.8.7

Code

import * as ng from "angular2/core";

@ng.Decorator({
...
})
export class MyClass{
     constructor(private el: ng.ElementRef) {
     }
}

Expected behavior:
If the isolatedModules flag is set to false:

...
MyClass = __decorate([
      ng.Directive({
            selector: '[my-selector]',
      }), 
      __metadata('design:paramtypes', [ng.ElementRef]) // <<<<<<<<<<<<<<<<<<<
], MyClass);

Actual behavior:

If the isolatedModules flag is set to true:

...
MyClass = __decorate([
      ng.Directive({
            selector: '[my-selector]',
      }), 
      __metadata('design:paramtypes', [Object]) // <<<<<<<<<<<<<<<<<<<<<<<
], MyClass);

[mhegazy]

there are differences that are expected in the emit when using this flag, but it should not be functionally different. this sample looks like a bug.

I can not get the different emitted code just using the snippet provided, so there is something else going on. can you share more context from this file.

[jpsfs]

Sorry, it seems that it is a problem within gulp-typescript and not typescript itself.
I'm closing the issue for now.

Nevertheless, here is a repo that can reproduce the bug:
https://github.com/jpsfs/typescript-angular-samples

[ivogabe]

@mhegazy I'm confused, has the behavior of isolatedModules been changed? I thought that the project would be compiled file by file, like what transpile does. But that doesn't seem to be what tsc really does?

[mhegazy]

The output should be the same as that of transpile. if not it is a bug.

[ivogabe]

Gulp-typescript uses transpile, and that emits Object, whereas tsc emits ng.ElementRef. So I think this would be a bug of TypeScript, as I have no idea why gulp-typescript would give a different result otherwise.

[yuit]

@Andy-MS you mind if I take this bug

[ghost]

OK. Here's what I was testing with:

// @experimentalDecorators: true
// @emitDecoratorMetadata: true
// @target: es5
// @isolatedModules: true

// @Filename: a.ts
export interface X {}

// @Filename: user.ts
import {X} from './a'
declare const decorator: MethodDecorator
export class C {
    @decorator
    myMethod(x: X) {}
}

When a.ts declares X as an interface, the parameter type is output as Object, but when X is a class, it is emitted as a_1.X.
So it appears that even with --isolatedModules, we are looking at information from a different module to affect emit.

[rbuckton]

@Andy-MS That is expected. We always serialize an interface as Object.

[yuit]

@rbuckton is this because interface has no value that one can refer to during run-time ?

[yuit]

@ivogabe so there is some inconsistency in our emitted results for sure. I am currently investigating. Though some quick clarification, just wonder why --isolatedModules specified by users make gulp-typescript behaves different since you guys call into TypeScript' api transpile function here and that function will always set isolatedModules to be true. let me know if I misunderstand something here...

[ivogabe]

Gulp-typescript has two different compile strategies. When you set isolatedModules, it will use a file based compiler, by calling the transpile function. With incremental compilation this is very fast, since only changed files will be recompiled. If you don't set isolatedModules, it will use a project based compiler. This works with a CompilerHost etcetera, and all files are passed to the compiler.
tsc always takes that second approach.

[ivogabe]

The problem is probably that only type information of the containing file is present with transpile. tsc does have type information of all source files but it shouldn't use that in the emit.