make the hooks returned iter type more concrete with a non-optional .return method and more

Author: shtaif

spec/tests/useSharedAsyncIter.spec.ts

@@ -72,7 +72,7 @@ describe('`useSharedAsyncIter` hook', () => {
       const yieldP2 = iterator2.next();
 
       {
-        await iterator1.return!();
+        await iterator1.return();
         const promiseStates = await Promise.all([yieldP1, yieldP2].map(checkPromiseState));
         expect(promiseStates).toStrictEqual([
           { state: 'FULFILLED', value: { done: true, value: undefined } },
@@ -81,7 +81,7 @@ describe('`useSharedAsyncIter` hook', () => {
       }
 
       {
-        await iterator2.return!();
+        await iterator2.return();
         const promiseStates = await Promise.all([yieldP1, yieldP2].map(checkPromiseState));
         expect(promiseStates).toStrictEqual([
           { state: 'FULFILLED', value: { done: true, value: undefined } },
@@ -174,16 +174,16 @@ describe('`useSharedAsyncIter` hook', () => {
         await Promise.all(iterators.map(it => it.next()));
         expect(mockSourceIterator.return).not.toHaveBeenCalled();
 
-        await iterators[2].return!();
+        await iterators[2].return();
         expect(mockSourceIterator.return).not.toHaveBeenCalled();
 
-        await iterators[1].return!();
+        await iterators[1].return();
         expect(mockSourceIterator.return).not.toHaveBeenCalled();
 
-        await iterators[0].return!();
+        await iterators[0].return();
         expect(mockSourceIterator.return).toHaveBeenCalledOnce();
 
-        await Promise.all(iterators.map(it => it.return!()));
+        await Promise.all(iterators.map(it => it.return()));
         expect(mockSourceIterator.return).toHaveBeenCalledOnce();
       });
 
@@ -205,12 +205,12 @@ describe('`useSharedAsyncIter` hook', () => {
         await Promise.all(iterators.map(it => it.next()));
         expect(mockSourceIterator.return).not.toHaveBeenCalled();
 
-        const returnCallsPromise = Promise.all(iterators.map(it => it.return!()));
+        const returnCallsPromise = Promise.all(iterators.map(it => it.return()));
         expect(mockSourceIterator.return).toHaveBeenCalledOnce();
 
         await returnCallsPromise;
 
-        await Promise.all(iterators.map(it => it.return!()));
+        await Promise.all(iterators.map(it => it.return()));
         expect(mockSourceIterator.return).toHaveBeenCalledOnce();
       });
     }

src/useSharedAsyncIter/index.ts

@@ -74,13 +74,16 @@ export { useSharedAsyncIter };
  * }
  * ```
  */
-function useSharedAsyncIter<T>(value: AsyncIterable<T>): AsyncIterable<T>;
+function useSharedAsyncIter<T>(value: AsyncIterable<T>): {
+  [Symbol.asyncIterator](): {
+    next(): Promise<IteratorResult<T, undefined>>;
+    return(): Promise<IteratorReturnResult<undefined>>;
+  };
+};
 function useSharedAsyncIter<T>(value: T): T;
 function useSharedAsyncIter(value: unknown): MaybeAsyncIterable<unknown> {
   return useAsyncIterMemo(
     value => (!isAsyncIter(value) ? value : asyncIterShare<unknown>()(value)),
     [value]
   );
 }
-
-// TODO: Enhance `useSharedAsyncIter`'s returned iter to have the `.return` method as NOT optional?