[pull] master from facebook:master

packages/react-noop-renderer/src/createReactNoop.js

@@ -533,6 +533,13 @@ function createReactNoop(reconciler: Function, useMutation: boolean) {
           newChildren: Array<Instance | TextInstance>,
         ): void {
           container.pendingChildren = newChildren;
+          if (
+            newChildren.length === 1 &&
+            newChildren[0].text === 'Error when completing root'
+          ) {
+            // Trigger an error for testing purposes
+            throw Error('Error when completing root');
+          }
         },
 
         replaceContainerChildren(

packages/react-reconciler/src/ReactFiberWorkLoop.js

@@ -1285,6 +1285,13 @@ function handleError(root, thrownValue) {
         // boundary.
         workInProgressRootExitStatus = RootFatalErrored;
         workInProgressRootFatalError = thrownValue;
+        // Set `workInProgress` to null. This represents advancing to the next
+        // sibling, or the parent if there are no siblings. But since the root
+        // has no siblings nor a parent, we set it to null. Usually this is
+        // handled by `completeUnitOfWork` or `unwindWork`, but since we're
+        // interntionally not calling those, we need set it here.
+        // TODO: Consider calling `unwindWork` to pop the contexts.
+        workInProgress = null;
         return null;
       }
 

packages/react-reconciler/src/__tests__/ReactIncrementalErrorHandling-test.internal.js

@@ -1658,4 +1658,16 @@ describe('ReactIncrementalErrorHandling', () => {
         'Please update the following components: Provider',
     ]);
   });
+
+  if (global.__PERSISTENT__) {
+    it('regression test: should fatal if error is thrown at the root', () => {
+      const root = ReactNoop.createRoot();
+      root.render('Error when completing root');
+      expect(Scheduler).toFlushAndThrow('Error when completing root');
+
+      const blockingRoot = ReactNoop.createBlockingRoot();
+      blockingRoot.render('Error when completing root');
+      expect(Scheduler).toFlushAndThrow('Error when completing root');
+    });
+  }
 });

packages/shared/forks/ReactFeatureFlags.testing.www.js

@@ -48,6 +48,7 @@ export const disableUnstableRenderSubtreeIntoContainer = __EXPERIMENTAL__;
 export const warnUnstableRenderSubtreeIntoContainer = false;
 export const disableUnstableCreatePortal = __EXPERIMENTAL__;
 export const deferPassiveEffectCleanupDuringUnmount = false;
+export const runAllPassiveEffectDestroysBeforeCreates = false;
 export const isTestEnvironment = true;
 
 // Only used in www builds.