race continues to subscribe when won via complete or error

[cartant]

Bug Report

This is a re-write of the bug found in #4806.

Current Behavior

When a race is won by a source observable that completes or errors synchronously, the implementation continues to subscribe to subsequent source observables.

This does not happen if the source observable that wins the race does so by emitting a value notification.

Reproduction

This code:

import { defer, EMPTY, of, race, throwError } from "rxjs";
import { delay } from "rxjs/operators";

race(
  defer(() => {
    console.log("subscribed to 1");
    return of(1).pipe(delay(100));
  }),
  defer(() => {
    console.log("subscribed to EMPTY");
    return EMPTY;
  }),
  defer(() => {
    console.log("subscribed to 3");
    return of(3).pipe(delay(300));
  })
).subscribe({
  complete: () => console.log("won"),
  error: () => console.log("won with error")
});

will output:

subscribed to 1
subscribed to EMPTY
won
subscribed to 3

and this code:

race(
  defer(() => {
    console.log("subscribed to 1");
    return of(1).pipe(delay(100));
  }),
  defer(() => {
    console.log("subscribed to error");
    return throwError(new Error("kaboom"));
  }),
  defer(() => {
    console.log("subscribed to 3");
    return of(3).pipe(delay(300));
  })
).subscribe({
  complete: () => console.log("won"),
  error: () => console.log("won with error")
});

will output:

subscribed to 1
subscribed to error
won with error
subscribed to 3

Expected behavior

For races won via completion or error, the behaviour should be like this code and subscriptions to subsequent source observables should not be made:

race(
  defer(() => {
    console.log("subscribed to 1");
    return of(1).pipe(delay(100));
  }),
  defer(() => {
    console.log("subscribed to 2");
    return of(2);
  }),
  defer(() => {
    console.log("subscribed to 3");
    return of(3).pipe(delay(300));
  })
).subscribe({
  complete: () => console.log("won"),
  error: () => console.log("won with error")
});

will output:

subscribed to 1
subscribed to 2
won

Environment

• Runtime: Node
• RxJS version: 6.5.2