Support defaultProps resolution

packages/react-debug-tools/src/ReactDebugHooks.js

@@ -481,6 +481,21 @@ function inspectHooksOfForwardRef<Props, Ref>(
   return buildTree(rootStack, readHookLog);
 }
 
+function resolveDefaultProps(Component, baseProps) {
+  if (Component && Component.defaultProps) {
+    // Resolve default props. Taken from ReactElement
+    const props = Object.assign({}, baseProps);
+    const defaultProps = Component.defaultProps;
+    for (let propName in defaultProps) {
+      if (props[propName] === undefined) {
+        props[propName] = defaultProps[propName];
+      }
+    }
+    return props;
+  }
+  return baseProps;
+}
+
 export function inspectHooksOfFiber(fiber: Fiber) {
   if (
     fiber.tag !== FunctionComponent &&
@@ -495,6 +510,9 @@ export function inspectHooksOfFiber(fiber: Fiber) {
   getPrimitiveStackCache();
   let type = fiber.type;
   let props = fiber.memoizedProps;
+  if (type !== fiber.elementType) {
+    props = resolveDefaultProps(type, props);
+  }
   // Set up the current hook so that we can step through and read the
   // current state from them.
   currentHook = (fiber.memoizedState: Hook);

packages/react-debug-tools/src/__tests__/ReactHooksInspectionIntegration-test.internal.js

@@ -214,4 +214,34 @@ describe('ReactHooksInspectionIntergration', () => {
       },
     ]);
   });
+
+  it('should support defaultProps and lazy', async () => {
+    let Suspense = React.Suspense;
+
+    function Foo(props) {
+      let [value] = React.useState(props.defaultValue.substr(0, 3));
+      return <div>{value}</div>;
+    }
+    Foo.defaultProps = {
+      defaultValue: 'default',
+    };
+
+    async function fakeImport(result) {
+      return {default: result};
+    }
+
+    let LazyFoo = React.lazy(() => fakeImport(Foo));
+
+    let renderer = ReactTestRenderer.create(
+      <Suspense fallback="Loading...">
+        <LazyFoo />
+      </Suspense>,
+    );
+
+    await LazyFoo;
+
+    let childFiber = renderer.root._currentFiber();
+    let tree = ReactDebugTools.inspectHooksOfFiber(childFiber);
+    expect(tree).toEqual([{name: 'State', value: 'def', subHooks: []}]);
+  });
 });