feat(Subject.create): Removed the deprecated Subject.create method.

BREAKING CHANGE: Removed the deprecated `Subject.create` method. If you need to create an object that is "half Observable, half Observer", you'll need to either bolt `next`, `error`, and `complete` handlers onto an `Observable` and property type the return... or you'll need to create your own class that is backed by an `Observable`. In any case, if the `Observer` and the `Observable` are so unrelated that you have to bolt them together, you're probably better off with those two objects separately. This is why `Subject.create` has been deprecated for so long.

packages/rxjs/spec/Subject-spec.ts

@@ -1,6 +1,5 @@
 import { expect } from 'chai';
 import { Subject, Observable, AsyncSubject, Observer, of, config, Subscription, Subscriber, noop, operate } from 'rxjs';
-import { AnonymousSubject } from 'rxjs/internal/Subject';
 import { delay } from 'rxjs/operators';
 import { TestScheduler } from 'rxjs/testing';
 import { observableMatcher } from './helpers/observableMatcher';
@@ -448,104 +447,6 @@ describe('Subject', () => {
     expect(subject.observed).to.equal(false);
   });
 
-  it('should have a static create function that works', () => {
-    expect(Subject.create).to.be.a('function');
-    const source = of(1, 2, 3, 4, 5);
-    const nexts: number[] = [];
-    const output: any[] = [];
-
-    let error: any;
-    let complete = false;
-    let outputComplete = false;
-
-    const destination = {
-      closed: false,
-      next: function (x: number) {
-        nexts.push(x);
-      },
-      error: function (err: any) {
-        error = err;
-        this.closed = true;
-      },
-      complete: function () {
-        complete = true;
-        this.closed = true;
-      },
-    };
-
-    const sub: Subject<any> = Subject.create(destination, source);
-
-    sub.subscribe({
-      next: function (x: number) {
-        output.push(x);
-      },
-      complete: () => {
-        outputComplete = true;
-      },
-    });
-
-    sub.next('a');
-    sub.next('b');
-    sub.next('c');
-    sub.complete();
-
-    expect(nexts).to.deep.equal(['a', 'b', 'c']);
-    expect(complete).to.be.true;
-    expect(error).to.be.a('undefined');
-
-    expect(output).to.deep.equal([1, 2, 3, 4, 5]);
-    expect(outputComplete).to.be.true;
-  });
-
-  it('should have a static create function that works also to raise errors', () => {
-    expect(Subject.create).to.be.a('function');
-    const source = of(1, 2, 3, 4, 5);
-    const nexts: number[] = [];
-    const output: number[] = [];
-
-    let error: any;
-    let complete = false;
-    let outputComplete = false;
-
-    const destination = {
-      closed: false,
-      next: function (x: number) {
-        nexts.push(x);
-      },
-      error: function (err: any) {
-        error = err;
-        this.closed = true;
-      },
-      complete: function () {
-        complete = true;
-        this.closed = true;
-      },
-    };
-
-    const sub: Subject<any> = Subject.create(destination, source);
-
-    sub.subscribe({
-      next: function (x: number) {
-        output.push(x);
-      },
-      complete: () => {
-        outputComplete = true;
-      },
-    });
-
-    sub.next('a');
-    sub.next('b');
-    sub.next('c');
-    sub.error('boom');
-
-    expect(nexts).to.deep.equal(['a', 'b', 'c']);
-    expect(complete).to.be.false;
-    expect(error).to.equal('boom');
-
-    expect(output).to.deep.equal([1, 2, 3, 4, 5]);
-    expect(outputComplete).to.be.true;
-  });
-
   it('should be an Observer which can be given to Observable.subscribe', (done) => {
     const source = of(1, 2, 3, 4, 5);
     const subject = new Subject<number>();
@@ -781,30 +682,3 @@ describe('Subject', () => {
     expect(results).to.deep.equal([1, 1, 2, 2, 'complete']);
   });
 });
-
-describe('AnonymousSubject', () => {
-  it('should be exposed', () => {
-    expect(AnonymousSubject).to.be.a('function');
-  });
-
-  it('should not be eager', () => {
-    let subscribed = false;
-
-    const subject = Subject.create(
-      null,
-      new Observable((observer: Observer<any>) => {
-        subscribed = true;
-        const subscription = of('x').subscribe(observer);
-        return () => {
-          subscription.unsubscribe();
-        };
-      })
-    );
-
-    const observable = subject.asObservable();
-    expect(subscribed).to.be.false;
-
-    observable.subscribe();
-    expect(subscribed).to.be.true;
-  });
-});

packages/rxjs/src/internal/Subject.ts

@@ -40,15 +40,6 @@ export class Subject<T> extends Observable<T> implements SubscriptionLike {
   /** @deprecated Internal implementation detail, do not use directly. Will be made internal in v8. */
   thrownError: any = null;
 
-  /**
-   * Creates a "subject" by basically gluing an observer to an observable.
-   *
-   * @deprecated Recommended you do not use. Will be removed at some point in the future. Plans for replacement still under discussion.
-   */
-  static create: (...args: any[]) => any = <T>(destination: Observer<T>, source: Observable<T>): AnonymousSubject<T> => {
-    return new AnonymousSubject<T>(destination, source);
-  };
-
   constructor() {
     // NOTE: This must be here to obscure Observable's constructor.
     super();
@@ -146,31 +137,3 @@ export class Subject<T> extends Observable<T> implements SubscriptionLike {
     return new Observable((subscriber) => this.subscribe(subscriber));
   }
 }
-
-export class AnonymousSubject<T> extends Subject<T> {
-  constructor(
-    /** @deprecated Internal implementation detail, do not use directly. Will be made internal in v8. */
-    public destination?: Observer<T>,
-    /** @internal */
-    protected _source?: Observable<T>
-  ) {
-    super();
-  }
-
-  next(value: T) {
-    this.destination?.next?.(value);
-  }
-
-  error(err: any) {
-    this.destination?.error?.(err);
-  }
-
-  complete() {
-    this.destination?.complete?.();
-  }
-
-  /** @internal */
-  protected _subscribe(subscriber: Subscriber<T>): Subscription {
-    return this._source?.subscribe(subscriber) ?? Subscription.EMPTY;
-  }
-}