Export typeUtils from flipper-common

Reviewed By: passy

Differential Revision: D36098166

fbshipit-source-id: 0f3da1d17da8ff6d08bc05abe73f9657df3bc3b8

desktop/flipper-common/src/index.tsx

@@ -49,6 +49,7 @@ export {
   deserializeRemoteError,
 } from './utils/errors';
 export {createControlledPromise} from './utils/controlledPromise';
+export * from './utils/typeUtils';
 export * from './GK';
 export * from './clientUtils';
 export * from './settings';

desktop/flipper-common/src/utils/typeUtils.tsx

@@ -0,0 +1,14 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ */
+
+// Typescript doesn't know Array.filter(Boolean) won't contain nulls.
+// So use Array.filter(notNull) instead.
+export function notNull<T>(x: T | null | undefined): x is T {
+  return x !== null && x !== undefined;
+}