Include flow comments in compiled output

[zpao]

This should make it such that we can properly run flow in projects consuming fbjs.

(Sorry for the package.json noise, npm3 sorts on writing)

[zpao]

Well this can't be right… that diff definitely has some syntax errors. https://gist.github.com/zpao/29cc0a4bd03791d08cd1

I'll make this so that we run tests with this transform and catch things like that.

[zpao]

And now it's works because @sebmck is awesome.

[yungsters]

This change causes dependent projects to suddenly have many false flow errors. A cursory investigation shows that 1) flow does not like the code generated by babel (e.g. _createClass assigns properties to an object without a defined shape), and 2) generic types (e.g. Foo<T>) are not preserved and become invalid identifiers.

[zpao]

What's the best move? Revert?

[sebmck]

Setting { "loose": "es6.classes" } should be enough to make Flow understand the class structure. Not entirely clear on Foo<T> but if it's a Babel issue let me know and I'll fix it.

[yungsters]

Cool, I'll try { "loose": "es6.classes" }. Thanks!

I might have found another issue:

function everyObject(
  object: ?Object,
  callback: (value: any, name: string, object: Object) => any,
  context?: any,
): boolean {

...is being transpiled into...

function everyObject(object /*: ?Object*/, callback /*: (value: any, name: string, object: Object) => any*/, context? /*:: ?: any*/) /*: boolean*/ {

The problem is context?, which is invalid syntax.

---

For context, foo?: string is different from foo: ?string. The former is an optional argument that, if supplied, must be a non-null string. The latter is a required argument that is a nullable string. You can also have foo?: ?string, which is an optional argument that, if supplied, is a nullable string.

[sebmck]

That'd be because the flow transformer has been blacklisted which is responsible for stripping those. Fixed via babel-plugins/babel-plugin-flow-comments@df836e49e846fbec375d7f4de5f8c0a182333487 and released as of babel-plugin-flow-comments@1.0.9.

[yungsters]

Great. I'll give babel-plugin-flow-comments@1.0.9 a spin.

I'll open an issue for the generic types on https://github.com/babel-plugins/babel-plugin-flow-comments.

[yungsters]

Opened babel-plugins/babel-plugin-flow-comments#15.