Fix shallow renderer not allowing hooks in forwardRef render functions (facebook#15100)

* test: Add test for shallow + forwardRef + hook

* fix(react-test-renderer): shallow forwardRef hooks

Author: eps1lon

packages/react-test-renderer/src/ReactShallowRenderer.js

@@ -521,9 +521,7 @@ class ReactShallowRenderer {
     if (this._instance) {
       this._updateClassComponent(element, this._context);
     } else {
-      if (isForwardRef(element)) {
-        this._rendered = element.type.render(element.props, element.ref);
-      } else if (shouldConstruct(element.type)) {
+      if (shouldConstruct(element.type)) {
         this._instance = new element.type(
           element.props,
           this._context,
@@ -565,11 +563,15 @@ class ReactShallowRenderer {
         ReactCurrentDispatcher.current = this._dispatcher;
         this._prepareToUseHooks(element.type);
         try {
-          this._rendered = element.type.call(
-            undefined,
-            element.props,
-            this._context,
-          );
+          if (isForwardRef(element)) {
+            this._rendered = element.type.render(element.props, element.ref);
+          } else {
+            this._rendered = element.type.call(
+              undefined,
+              element.props,
+              this._context,
+            );
+          }
         } finally {
           ReactCurrentDispatcher.current = prevDispatcher;
         }

packages/react-test-renderer/src/__tests__/ReactShallowRendererHooks-test.js

@@ -304,4 +304,22 @@ describe('ReactShallowRenderer with hooks', () => {
       </div>,
     );
   });
+
+  it('should work with with forwardRef + any hook', () => {
+    const SomeComponent = React.forwardRef((props, ref) => {
+      const randomNumberRef = React.useRef({number: Math.random()});
+
+      return (
+        <div ref={ref}>
+          <p>The random number is: {randomNumberRef.current.number}</p>
+        </div>
+      );
+    });
+
+    const shallowRenderer = createRenderer();
+    let firstResult = shallowRenderer.render(<SomeComponent />);
+    let secondResult = shallowRenderer.render(<SomeComponent />);
+
+    expect(firstResult).toEqual(secondResult);
+  });
 });