Warn if findDOMNode is used inside render

Need to reset current owner to null before committing

scripts/fiber/tests-passing-except-dev.txt

@@ -1,6 +1,3 @@
-src/renderers/__tests__/ReactComponentLifeCycle-test.js
-* warns if findDOMNode is used inside render
-
 src/renderers/__tests__/ReactComponentTreeHook-test.js
 * uses displayName or Unknown for classic components
 * uses displayName, name, or ReactComponent for modern components

scripts/fiber/tests-passing.txt

@@ -550,6 +550,7 @@ src/renderers/__tests__/ReactComponentLifeCycle-test.js
 * should correctly determine if a component is mounted
 * should correctly determine if a null component is mounted
 * isMounted should return false when unmounted
+* warns if findDOMNode is used inside render
 * should not throw when updating an auxiliary component
 * should allow state updates in componentDidMount
 * should call nested lifecycle methods in the right order

src/renderers/dom/shared/findDOMNode.js

@@ -26,10 +26,14 @@ let findStack = function(arg) {
 
 const findDOMNode = function(componentOrElement : Element | ?ReactComponent<any, any, any>) : null | Element | Text {
   if (__DEV__) {
-    var owner = ReactCurrentOwner.current;
-    if (owner !== null && '_warnedAboutRefsInRender' in owner) {
+    var owner = (ReactCurrentOwner.current : any);
+    if (owner !== null) {
+      var isFiber = typeof owner.tag === 'number';
+      var warnedAboutRefsInRender = isFiber ?
+        owner.stateNode._warnedAboutRefsInRender :
+        owner._warnedAboutRefsInRender;
       warning(
-        (owner: any)._warnedAboutRefsInRender,
+        warnedAboutRefsInRender,
         '%s is accessing findDOMNode inside its render(). ' +
         'render() should be a pure function of props and state. It should ' +
         'never access something that requires stale data from the previous ' +
@@ -37,7 +41,11 @@ const findDOMNode = function(componentOrElement : Element | ?ReactComponent<any,
         'componentDidUpdate instead.',
         getComponentName(owner) || 'A component'
       );
-      (owner: any)._warnedAboutRefsInRender = true;
+      if (isFiber) {
+        owner.stateNode._warnedAboutRefsInRender = true;
+      } else {
+        owner._warnedAboutRefsInRender = true;
+      }
     }
   }
   if (componentOrElement == null) {

src/renderers/shared/fiber/ReactFiberScheduler.js

@@ -349,6 +349,9 @@ module.exports = function<T, P, I, TI, PI, C, CX, PL>(config : HostConfig<T, P,
       'in React. Please file an issue.'
     );
 
+    // Reset this to null before calling lifecycles
+    ReactCurrentOwner.current = null;
+
     // Updates that occur during the commit phase should have Task priority
     const previousPriorityContext = priorityContext;
     priorityContext = TaskPriority;