Es6 default import support

[bobzhang]

It seems we already support export default.

export {
   $$default,
   $$default as default
}

See http://exploringjs.com/es6/ch_modules.html

const __default__ = «expression»;
export { __default__ as default }; 

That's what we did for default export

For default import,

external myFunction : unit -> unit = "my-module" [@@bs.default]
let () = myFunction ()

Expect generated ES6 code:

import myFunction from "my-module"
myFunction()

For commonjs

var myModule = require("my-module")
myModule.default ()

[kennetpostigo]

@bobzhang not sure if this is priority, it is a major factor for the public and internal apps we build at my job with bucklescript but first class support for dynamic imports would be great, there was an issue that @glennsl opened after we discussed this at length on discord: #2364

It was closed because someone made a library to enable dynamic imports in BS but it be nice to have this "embedded" in the bucklescript platform:
https://github.com/kMeillet/bs-dynamic-import/blob/master/src/DynamicImport.re

[kennetpostigo]

Heres the spec:
https://github.com/tc39/proposal-dynamic-import

Heres some writing on the feature:

• https://developers.google.com/web/updates/2017/11/dynamic-import
• http://2ality.com/2017/01/import-operator.html

It's been implemented in all major bundlers in the Javascript world and it allows shipping only code that needs to be executed per page, reducing overall js that needs to be loaded & parsed at a time. Making webapps snappier overall.

[bobzhang]

hi @kennetpostigo would you discuss it in another issue, this issue is just for default import, thanks!

[Gregoirevda]

@bobzhang would external myFunction : unit -> unit = "my-module" [@@bs.default] fix this issue?
apollographql/reason-apollo#80

[schutm]

Any progress on this one?