Support for Bluebird coroutines

[guybedford]

If users want to use Bluebird promises for performance, we should provide an easy option to use this transformer without having to do more than setting the option and installing bluebird.

[kirly-af]

Anything new concerning this issue ?

[guybedford]

I'm not sure if output to Bluebird coroutines is still provided in Babel 6 actually? Do you know? If it is, we can certainly add an option here.

Otherwise it may be worth trying to install a third-party Babel plugin to try this out.

[guybedford]

Ok it is still supported via the plugin at http://babeljs.io/docs/plugins/transform-async-to-module-method/.

It would be possible to integrate this manually by installing it and configuring the plugin, but we could integrate this as an option as well potentially.

[kirly-af]

Here is what I did:

jspm install npm:babel-plugin-transform-async-to-module-method
jspm install npm:bluebird

And below is a part of jspm.config.js file:

SystemJS.config({
  transpiler: "plugin-babel",
  packages: {
    "mypackage": {
      "format": "esm",
      "main": "main.js",
      "meta": {
        "*.js": {
          "loader": "plugin-babel",
          "babelOptions": {
            "plugins": [
              ["transform-async-to-module-method", {
                "module": "bluebird",
                "method": "coroutine"
              }]
            ]
          }
        }
      }
    }
  }
});

However, Bluebird library does not seem to be loaded

typeof Promise.setScheduler // undefined

Furthermore, my async functions are still transpiled with async-to-regenerator plugin.

Source:

let foo = async () => {
  let ret = await bar()
}

Transpiled:

foo = function () {
        var ref = _asyncToGenerator(_regeneratorRuntime.mark(function _callee() {
// ...

This happens even when I do not specify any options to the plugin (ie. when I do not try to use bluebird coroutines).

      "meta": {
        "*.js": {
          "loader": "plugin-babel",
          "babelOptions": {
            "plugins": [
              ["transform-async-to-module-method"]
            ]
          }
        }
      }

Being able to set this behavior by passing a simple option sounds good to me. I guess most Angular (< 2) developers who start working with ES6+ will need to use Bluebird coroutines to work with async/await.

[guybedford]

Are you sure the configuration is applying? Because the plugin name should be babel-plugin-transform-async-to-module-method I think?

[kirly-af]

Well, from the plugin documentation that you can find here or here, the usage in .babelrc is the following:

// without options
{
  "plugins": ["transform-async-to-module-method"]
}

// with options
{
  "plugins": [
    ["transform-async-to-module-method", {
      "module": "bluebird",
      "method": "coroutine"
    }]
  ]
}

I tried to replace it with babel-plugin-transform-async-to-module-method and it did not help (same output). I am a bit confused actually. What name should I use ? The one of babel docs, the package name, or the name specified in the map section of the jspm.config.js file ?

This is not clearly explained in JSPM docs:

plugin-babel README:

babelOptions: {
  plugins: [
    [ "react-transform", {
      "transforms": [{"transform": "react-transform-jspm-hmr"}]
    }]
  ]
}

jspm beta docs:

"babelOptions": {
  "plugins": ["babel-plugin-transform-react-jsx"]
}

Btw, would it help if I provide my full jspm.config.js ?

[guybedford]

I've updated the options example at https://github.com/systemjs/plugin-babel#custom-presets-and-transforms to show using bluebird coroutines.

In terms of loading bluebird, it's probably best to have a script tag in the head, but you could also import it via System.import. Then to use the same version of bluebird in SystemJS you could try something like System.set('bluebird', System.newModule({ default: window.bluebird })).