fix: correct type inference for props when initialProps is used (#1421)

* fix: correct type inference for props when initialProps is used

* Update src/__tests__/renderHook.test.tsx

* refactor: simplify type of Renderhook options

---------

Co-authored-by: pierrezimmermann <pierrez@nam.tech>
Co-authored-by: Maciej Jastrzebski <mdjastrzebski@gmail.com>

Author: 3 people

src/__tests__/renderHook.test.tsx

@@ -60,3 +60,37 @@ test('allows wrapper components', async () => {
 
   expect(result.current).toEqual('provided');
 });
+
+const useMyHook = (param: number | undefined) => {
+  return param;
+};
+
+test('props type is infered correctly when initial props is defined', () => {
+  const { result, rerender } = renderHook(
+    (num: number | undefined) => useMyHook(num),
+    {
+      initialProps: 5,
+    }
+  );
+
+  expect(result.current).toBe(5);
+
+  rerender(6);
+
+  expect(result.current).toBe(6);
+});
+
+test('props type is inferred correctly when initial props is explicitly undefined', () => {
+  const { result, rerender } = renderHook(
+    (num: number | undefined) => useMyHook(num),
+    {
+      initialProps: undefined,
+    }
+  );
+
+  expect(result.current).toBeUndefined();
+
+  rerender(6);
+
+  expect(result.current).toBe(6);
+});

src/renderHook.tsx

@@ -8,16 +8,10 @@ export type RenderHookResult<Result, Props> = {
   unmount: () => void;
 };
 
-export type RenderHookOptions<Props> = Props extends
-  | object
-  | string
-  | number
-  | boolean
-  ? {
-      initialProps: Props;
-      wrapper?: ComponentType<any>;
-    }
-  : { wrapper?: ComponentType<any>; initialProps?: never } | undefined;
+export type RenderHookOptions<Props> = {
+  initialProps?: Props;
+  wrapper?: ComponentType<any>;
+};
 
 export function renderHook<Result, Props>(
   renderCallback: (props: Props) => Result,