Move 'behavior' to be a method on ObservableScope

src/state/Behavior.ts

@@ -5,9 +5,7 @@ SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
 Please see LICENSE in the repository root for full details.
 */
 
-import { BehaviorSubject, distinctUntilChanged, Observable } from "rxjs";
-
-import { type ObservableScope } from "./ObservableScope";
+import { BehaviorSubject } from "rxjs";
 
 /**
  * A stateful, read-only reactive value. As an Observable, it is "hot" and
@@ -26,38 +24,3 @@ export type Behavior<T> = Omit<BehaviorSubject<T>, "next" | "observers">;
 export function constant<T>(value: T): Behavior<T> {
   return new BehaviorSubject(value);
 }
-
-declare module "rxjs" {
-  interface Observable<T> {
-    /**
-     * Converts this Observable into a Behavior. This requires the Observable to
-     * synchronously emit an initial value.
-     */
-    behavior(scope: ObservableScope): Behavior<T>;
-  }
-}
-
-const nothing = Symbol("nothing");
-
-Observable.prototype.behavior = function <T>(
-  this: Observable<T>,
-  scope: ObservableScope,
-): Behavior<T> {
-  const subject$ = new BehaviorSubject<T | typeof nothing>(nothing);
-  // Push values from the Observable into the BehaviorSubject.
-  // BehaviorSubjects have an undesirable feature where if you call 'complete',
-  // they will no longer re-emit their current value upon subscription. We want
-  // to support Observables that complete (for example `of({})`), so we have to
-  // take care to not propagate the completion event.
-  this.pipe(scope.bind(), distinctUntilChanged()).subscribe({
-    next(value) {
-      subject$.next(value);
-    },
-    error(err) {
-      subject$.error(err);
-    },
-  });
-  if (subject$.value === nothing)
-    throw new Error("Behavior failed to synchronously emit an initial value");
-  return subject$ as Behavior<T>;
-};