WIP: Adding lettable operators

[benlesh]

This is a WIP, do not merge.

Just planting a flag so people see progress being made.

The overall idea here is that inevitably you'll be able to do this:

import { map, filter } from 'rxjs/operators';

myObservable
  .let(filter(x => x % 2 === 0))
  .let(map(x => x + x))
  .subscribe(x => console.log(x))

I've got a lot of plans here, and there's clearly a lot of work to do. I'd just ask people to refrain from making PRs against this branch until they've chatted with me about it first, I'm still getting this idea to gel within this repository, and how we're going to migrate things toward a more T-Rx project.

[benlesh]

Also of note: There should be NO BREAKING CHANGES in in this PR. This should be able to ship with the next minor version

[rxjs-bot]

	Warnings
⚠️	❗ Big PR (1)

	Messages
📖

(1) : Pull Request size seems relatively large. If Pull Request contains multiple changes, split each into separate PR will helps faster, easier review.

CJS: 3646.0KB, global: 688.1KB (gzipped: 129.5KB), min: 139.4KB (gzipped: 30.0KB)

Generated by 🚫 dangerJS

[coveralls]

Coverage decreased (-0.003%) to 97.731% when pulling 2cc5d75 on benlesh:lettable-start into 70eaafc on ReactiveX:master.

[coveralls]

Coverage decreased (-0.001%) to 97.733% when pulling cd7e7dd on benlesh:lettable-start into 70eaafc on ReactiveX:master.

[coveralls]

Coverage increased (+0.0006%) to 97.735% when pulling cd7e7dd on benlesh:lettable-start into 70eaafc on ReactiveX:master.

[coveralls]

Coverage decreased (-0.001%) to 97.733% when pulling 9974fc2 on benlesh:lettable-start into 70eaafc on ReactiveX:master.

[coveralls]

Coverage increased (+0.0003%) to 97.734% when pulling 4ccf794 on benlesh:lettable-start into 70eaafc on ReactiveX:master.

[coveralls]

Coverage increased (+0.002%) to 97.736% when pulling 408a2af on benlesh:lettable-start into 70eaafc on ReactiveX:master.

[coveralls]

Coverage increased (+0.004%) to 97.738% when pulling 408a2af on benlesh:lettable-start into 70eaafc on ReactiveX:master.

[coveralls]

Coverage increased (+0.005%) to 97.739% when pulling 2f12572 on benlesh:lettable-start into 70eaafc on ReactiveX:master.

[coveralls]

Coverage decreased (-0.003%) to 97.731% when pulling 2f12572 on benlesh:lettable-start into 70eaafc on ReactiveX:master.

[kwonoj]

I think we can move forward for now as changes are mostly non-breaking and no blocking issues to be changes in this specific PR. As discussed probably we need small chunk of PR for easier change tracking.

[kwonoj]

nit: we'll likely to have OperatorFunction<T, R=T> in next if we pick this up into, possible candidate for breaking changes.

[coveralls]

Coverage decreased (-0.4%) to 97.377% when pulling 762a4f9 on benlesh:lettable-start into d2a32f9 on ReactiveX:master.

[jasonaden]

It looks like both compose and pipe are left-to-right implementations. I believe most functional implementations of compose are right-to-left (so the value ends up being the return of the first function) and pipe (or a pipe operator) is used for left-to-right. Should this just be a pipe function as well as the current pipe on Observable.prototype? This would be more consistent for those coming from other functional languages/libraries.

[benlesh]

@jasonaden... you're exactly right... Ramda's compose is right to left. On it's own, it's not quite "pipe"... hmm

[coveralls]

Coverage increased (+0.002%) to 97.736% when pulling 408a2af on benlesh:lettable-start into 70eaafc on ReactiveX:master.

[marcinnajder]

hi

when I saw the fallowing code myObservable .let(filter(x => x % 2 === 0)) first time, I was wondering, is really type inference in TypeScript so good that the type of variable x will be inferred correctly ?

I did some investigation and it turned out that TypeScript version 2.4 is required. Does it mean that since RxJS 5.5 TS 2.4 will be required ?

marcin

[niieani]

Hi @benlesh. What you've done here is awesome!

I've started working on a project already using the lettable operators, however it's a bit of a hassle having to manually build rxjs on each computer that I checkout the source. Would you consider releasing a beta with what's currently on master, so that people could start playing with the new lettables?

Also, I take it all operators will eventually become lettables? I was missing some, like startWith, so I had to write my own for the time being, like this:

import {startWith as startWithOnThis} from 'rxjs/dist/cjs/operator/startWith'
export const startWith = (...elements) => (observable) => startWithOnThis.apply(observable, elements)

One more thing, aside from ramda using compose RTL, is there any other reason for renaming to pipe? I personally think compose sounds better. To me, pipe is an operation you specify after the command, not before the actual command, at least that's how I'm used to it in shell (i.e. a | b | c). Also, compose is used LTR in recompose, and I think in lodash it's called flow (that's a bad name, though).

PS
Love the "This is a WIP, do not merge." annotation next to a violet "MERGED" status. 🤣

[benlesh]

@nileani ... This will all be in 5.5 as soon as we're done porting them over. It shouldn't be too long. Sorry for the inconvenience.

[lock]

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