fix: correctly check for promise in useLoadData (#39)

* fix: correctly check for promise in useLoadData

* simplification

* simplification

* add unit test to ensure useLoadData handles thenable objects as promises

* improved comment

Author: NielsJPeschel

hooks/useLoadData/useLoadData.test.ts

@@ -442,4 +442,13 @@ describe('useLoadData', () => {
     expect(getSuccess).toHaveBeenCalledTimes(2);
     expect(getSuccess).toHaveBeenCalledWith('b');
   });
+
+  it('should treat a thenable object as a Promise', async () => {
+    const getThenableSuccess = jest.fn(() => ({then: (resolve: any) => resolve(successResult)}));
+
+    const {result} = renderHook(() => useLoadData(getThenableSuccess));
+    expect(result.current.isInProgress).toBe(true);
+    await waitFor(() => expect(result.current.isInProgress).toBe(false));
+    expect(result.current.result).toBe(successResult);
+  });
 });

hooks/useLoadData/useLoadData.ts

@@ -1,5 +1,5 @@
 import {useEffect, useState, useMemo} from 'react';
-import {ApiResponse, RetryResponse, ApiResponseBase, OptionalDependency, DependencyBase} from '../../types';
+import {ApiResponse, RetryResponse, ApiResponseBase, OptionalDependency, DependencyBase, Promisable} from '../../types';
 
 import {FetchData, NotUndefined} from './types';
 
@@ -30,6 +30,15 @@ function unboxApiResponse<T>(arg: ApiResponse<T> | T): T {
   }
 }
 
+function isPromise<T>(promisable: Promisable<T>): promisable is Promise<T> {
+  /*
+    Simply checking promisable instanceof Promise is not sufficient. 
+    Certain environments do not use native promises. Checking for promisable
+    to be thenable is a more comprehensive and conclusive test.
+  */
+  return promisable && typeof promisable === 'object' && 'then' in promisable && typeof promisable.then === 'function';
+}
+
 export interface LoadDataConfig {
   fetchWhenDepsChange?: boolean;
   maxRetryCount?: number;
@@ -184,7 +193,7 @@ export function useLoadData<T extends NotUndefined, Deps extends any[]>(
     }
   }, [counter, localFetchWhenDepsChange]);
 
-  const nonPromiseResult = initialPromise.res instanceof Promise ? undefined : initialPromise.res;
+  const nonPromiseResult = isPromise(initialPromise.res) ? undefined : initialPromise.res;
   const initialData = data || nonPromiseResult;
 
   // Initialize our pending data to one of three possible states:

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@optum/react-hooks",
-  "version": "1.0.4",
+  "version": "1.0.5-next.1",
   "description": "A reusable set of React hooks",
   "repository": "https://github.com/Optum/react-hooks",
   "license": "Apache 2.0",