Dart should support interoperability with TypeScript & CoffeeScript libraries

[DartBot]

This issue was originally filed by @Emasoft

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I post this as a separate proposal. The issue arised first in response to 20189 ( https://code.google.com/p/dart/issues/detail?id=20189 ).

PROBLEM: Interoperating with large JS libraries from Dart is challenging and painful. Many js libraries use scripts like TypeScript or CoffeScript to help improve type checking and usability. Dart is not able to understand those scripts files, making very difficult to migrate projects to Dart and making the transition without wasting to much time.

SOLUTION: Dart should support TypeScript for interoperability. This would allow an easier migration from the .Net ecosystem to Dart. It would allow the users to immediatly include and reuse their TypeScript libraries in Dart projects without wasting years of work. Supporting CoffeScript should also be very important, many very important libraries are written in CoffeScript todays.

To do a proper support of Typescript the following requisites have to be meet:

1. User should just "drag&drop" a Typescript library in the DartEditor and it should automatically recognize it and make it works as a interop package. No configuration necessary.

2. Typescript types and classes should be recognized when called from Dart code and included in the static type checking analysis at compile time. The errors should be marked on the Typescript source, not on the derived javascript code.

3. Autocompletition of the Dart Analyzer should support Typescript autocompletitions when editing Typescript files.

4. Interop syntax should be completely automated and hidden to the user. API access from Dart to Typescript and from Typescript to Dart should not require to write or regenerate additional code. Typescript sources should be modified at any time without being forced to modify/update the Dart code that import them.

5. Typescript source files should be debugged, imported and exported to pub packages with yaml files the same way the Dart source files are.

6. When called from Dart sources, all autocompletition, function declarations and auto-discovery informations of TypeScript analyzer should be still available and integrated with the Dart Analyzer. It should be possible to choose from an autocompletition list and call any class, variable or function availables in the imported Typescript library.

7. Static type checking should be applied to ensure that the correct types are passed as arguments to (or from) the TypeScript libraries.

The same requisites should be meet in adding CoffeeScript support.

Dart should not only be able to "eat" the javascript world, it should also be able to absorb the huge CoffeeScript and TypeScript ecosystem, because almost all modern web projects are made with a mix of these.

[sethladd]

I wonder if this is an issue for https://github.com/dart-lang/js-interop ?

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cc @justinfagnani.
Added Library-JS, Area-Library, Triaged labels.

[DartBot]

This comment was originally written by jdav...@pcprogramming.com

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Please escalate, this is a big deal.

[jacob314]

Set owner to @jacob314.
Added Accepted label.

[DavidSouther]

Is the opposite story going to be supported? EG if someone has an Angular2 component library written in Dart, should I just be able to take their output and link against it in my TS project?

[zoechi]

I think the https://github.com/dart-lang/dev_compiler project is supposed to support your scenario.

[jacob314]

The dev compiler is the best option for your scenario.

[denisoby]

I've tried to make my implementation of .d.ts -> dart2js annotations converter. Please, see https://github.com/denis-aes/DefinitelyTyped.dart

[sigmundch]

I'm about to close this issue as obsolete. Just want to provide some context:

There has been many efforts in this area since this bug was filed. We have improved the declarative @JS interop (aka package:js) and teams have been successful using tools like js_facade_gen to automatically generate Dart interop stubs from .d.ts declarations as well.

We don't have plans to make our compilers and tools to automatically recognize .d.ts or coffeescript, but instead we are investing in improving the building blocks that will make it very easy to create and maintain such language integrations outside our tools.

Next steps on our JS-interop journey is to support zero-cost static wrappers. Being static, these abstractions will add extra flexibility we need to adapt APIs when bridging between Dart and JS, but at the same time they are analyzable by our compilers and allows for a very low-cost interop at runtime.