Nitpick: Shouldn't Rx.pipe with no arguments return identity instead of noop?

[leewz]

https://github.com/ReactiveX/rxjs/blob/6.5.2/src/internal/util/pipe.ts#L25

if (!fns) {
    return noop as UnaryFunction<any, any>;
}

The composition of zero things should be the identity under composition, which is Rx.identity, not Rx.noop. That allows pipe(pipe(), pipe(f)) to be equivalent to pipe([].concat([], [f]), which is equivalent to f.

I'm new to RxJS, so I don't know if people rely on this behavior.

[cartant]

Yes, you're right. It should be identity, IMO, too.

Note that the pipe method returns this - the source observable - when called with no arguments:

rxjs/src/internal/Observable.ts

Lines 342 to 344 in 8cc6491

	if (operations.length === 0) {
	return this as any;
	}

[cartant]

Would you be able to open a PR with the fix?

[leewz]

Actually, the conditional in my issue is not a check for the empty array, but for no array at all.

There is no test for pipeFromArray(undefined) = noop. The function is marked as @internal. The conditional is actually unreachable from client code.