feat(hasCompleted): Add operator.

source/operators/hasCompleted-spec.ts

@@ -0,0 +1,33 @@
+/**
+ * @license Use of this source code is governed by an MIT-style license that
+ * can be found in the LICENSE file at https://github.com/cartant/rxjs-etc
+ */
+/*tslint:disable:no-unused-expression*/
+
+import { marbles } from "rxjs-marbles";
+import { hasCompleted } from "./hasCompleted";
+
+describe("hasCompleted", () => {
+
+    it("should emit nothing for a source that does not complete", marbles(m => {
+
+        const source =   m.cold("ab-cd-ef--");
+        const sourceSubs =      "^---------";
+        const expected =        "----------";
+
+        const destination = source.pipe(hasCompleted());
+        m.expect(destination).toBeObservable(expected);
+        m.expect(source).toHaveSubscriptions(sourceSubs);
+    }));
+
+    it("should emit 'true' when a source completes", marbles(m => {
+
+        const source =   m.cold("ab-cd-ef-|");
+        const sourceSubs =      "^--------!";
+        const expected = m.cold("---------(t|)", { t: true });
+
+        const destination = source.pipe(hasCompleted());
+        m.expect(destination).toBeObservable(expected);
+        m.expect(source).toHaveSubscriptions(sourceSubs);
+    }));
+});

source/operators/hasCompleted.ts

@@ -0,0 +1,11 @@
+/**
+ * @license Use of this source code is governed by an MIT-style license that
+ * can be found in the LICENSE file at https://github.com/cartant/rxjs-etc
+ */
+
+import { concat, of, OperatorFunction } from "rxjs";
+import { ignoreElements } from "rxjs/operators";
+
+export function hasCompleted<T>(): OperatorFunction<T, boolean> {
+    return source => concat(source.pipe(ignoreElements()), of(true));
+}