Compile TS to native JS modules

RxJS version: 5.4.3

Code to reproduce:

<script type="module">
import * as Rx from './node_modules/rxjs/Rx.js'
</script>

Expected behavior: There should be a way to load RxJS via native JS module

Actual behavior: Can’t access Rx when using JS modules (error: require is not defined)

[phaux]

Let’s sum up all the ES module quirks again:

1. Imports must include .js extensions, because they are basically relative urls that the browser will use to download scripts.
2. Imports of other libraries must use relative path (../node_modules/some-lib/dist/lib.js instead of just some-lib)
3. Typings (.d.ts files) should be in the same directory that the js files are. "typings" property of package.json is used only when importing a library using node syntax (using only the package name as the path, so it doesn’t work with ES modules)

(3) is actually the default behavior of TS. (1) and (2) would need a post processing script if TS wont implement it.

Post processing script pseudo code:

for (every Import statement) {

    if (Import points to other package) {
        
        path = find_relative_path_to('node_modules') + path
        path += read('package.json')['main'] // read main property from module's package.json

    }
    
    if (path points to directory) { path += '/index.js' }
    else { path += '.js' }

}

[phaux]

about extension

Take a look at the file @reactivex/rxjs/dist/esm2015/Observable.js. All the imports there should have .js extensions. Otherwise importing Observable into your app will fail with 404 error (e.g. ./util/root should be ./util/root.js). I worked around that by setting up URL rewriting in apache/nginx.

typings

Example code:

import {Observable} from '../node_modules/@reactivex/rxjs/dist/esm2015/Observable.js'

The detected type of Observable is any. It should work if the declarations from /dist/typings were also copied to /dist/esm2015.

It seems that tsc will only look at "typings" in package.json when importing a module using CJS/Node syntax (import "@reactivex/rxjs" without mentioning node_modules or subpath)