Declaration files for ESM and ES2015 builds

[OliverJAsh]

When I try to import from rxjs-etc/esm2015/operators/delayUntil, I get an error: Could not find a declaration file for module 'rxjs-etc/esm2015/operators/delayUntil'.

My workaround:

// modules.d.ts
declare module 'rxjs-etc/esm2015/operators/delayUntil' {
  export { delayUntil } from 'rxjs-etc/operators/delayUntil';
}

Perhaps this library should enable declaration for the ESM and ES2015 builds, so we don't have to do this?

[cartant]

Hmm, the intention is for those to be consumed by the bundler, rather than directly.

[OliverJAsh]

I guess that makes sense when importing from the root, since the package manifest will redirect the bundler to one of the builds, but in this case I want to import from a sub module. Unless I use something webpack configuration to rewrite my paths.

[cartant]

Bundler configurations are the worst. There should be a package.json in the operators directory, though, so maybe - just maybe - using that import location might work?

import { delayUntil } from "rxjs-etc/esm2015/operators";

[OliverJAsh]

For that to work I think we would need to add a package.json and declarations inside that folder?

[cartant]

I just had a look at the dist and there isn't a package.json in the esm2015/operators directory. Yeah, if you create one it might solve the problem. You should be able to tell it the relative path to the declarations. Have a look at the package.json that's in source/operators for an example:

https://github.com/cartant/rxjs-etc/blob/master/source/operators/package.json

[cartant]

I've had the chance to play with it. If the following package.json is added to esm2015/operators it works fine, for me:

{
  "name": "rxjs-etc/operators",
  "main": "./index.js",
  "typings": "../../operators/index.d.ts",
  "sideEffects": false
}

I suppose I can add those to the distributions, but, TBH, I'm also inclined to bump all of my packages by a major version and publish them as ES modules targeting es2019. I'm so over this stuff.

[OliverJAsh]

IIUC, that would allow importing rxjs-etc/esm2015/operators, but not from rxjs-etc/esm2015/operators/{subModule}? That's why I wonder if it's better to just emit declarations into all build folders. 🤔

I'm so over this stuff.

Completely agree. We're using these modules on Node as well, so not sure how exactly ESM work there yet.

[cartant]

That's why I wonder if it's better to just emit declarations into all build folders. 🤔

Yeah, I'm inclined to agree.

[cartant]

FYI, I'm giving serious consideration to exporting es2020 CommonJS via main and es2020 ES modules via exports. Hopefully, that would fix this stuff once and for all.

See https://nodejs.org/api/esm.html#esm_package_exports

This allows defining a different entry point for Node.js versions that support ECMAScript modules and versions that don't, for example

{
  "main": "./main-legacy.cjs",
  "exports": {
    ".": "./main-modern.cjs"
  }
}

Also https://nodejs.org/api/esm.html#esm_conditional_exports

And https://medium.com/@nodejs/announcing-core-node-js-support-for-ecmascript-modules-c5d6dc29b663

And webpack/webpack#9509