feat(react-dom): Add async act (#37554)

* feat(react-dom): Add async act typings

* Update version

* Normalize typing with react-test-renderer

types/react-dom/index.d.ts

@@ -1,4 +1,4 @@
-// Type definitions for React (react-dom) 16.8
+// Type definitions for React (react-dom) 16.9
 // Project: http://facebook.github.io/react/
 // Definitions by: Asana <https://asana.com>
 //                 AssureSign <http://www.assuresign.com>

types/react-dom/react-dom-tests.tsx

@@ -185,9 +185,8 @@ describe('React dom test utils', () => {
         it('accepts a sync callback that is void', () => {
             ReactTestUtils.act(() => {});
         });
-        it('rejects an async callback even if void', () => {
-            // $ExpectError
-            ReactTestUtils.act(async () => {});
+        it('accepts an async callback that is void', async () => {
+            await ReactTestUtils.act(async () => {});
         });
         it('rejects a callback that returns null', () => {
             // $ExpectError

types/react-dom/test-utils/index.d.ts

@@ -291,8 +291,10 @@ export function createRenderer(): ShallowRenderer;
  * @see https://reactjs.org/blog/2019/02/06/react-v16.8.0.html#testing-hooks
  */
 // the "void | undefined" is here to forbid any sneaky "Promise" returns.
-// the actual return value is always a "DebugPromiseLike".
 export function act(callback: () => void | undefined): DebugPromiseLike;
+// the "void | undefined" is here to forbid any sneaky return values
+// tslint:disable-next-line: void-return
+export function act(callback: () => Promise<void | undefined>): Promise<undefined>;
 
 // Intentionally doesn't extend PromiseLike<never>.
 // Ideally this should be as hard to accidentally use as possible.

types/react-dom/tslint.json

@@ -7,4 +7,4 @@
         "no-unnecessary-generics": false,
         "no-unnecessary-type-assertion": false
     }
-}
+}