Implement Task priority

Task priority is similar to Synchronous priority. Both are flushed in
the current tick. Synchronous priority is flushed immediately (e.g. sync
work triggered by setState will flush before setState exits), where as
Task is flushed after the current batch of work is committed.

Currently used for batchedUpdates and nested sync updates. Task should
also be used for componentDidUpdate/Mount and error boundary work. I'll
add this in a later commit.

Author: acdlite

scripts/fiber/tests-failing.txt

@@ -554,9 +554,6 @@ src/renderers/shared/stack/reconciler/__tests__/ReactCompositeComponent-test.js
 src/renderers/shared/stack/reconciler/__tests__/ReactCompositeComponentNestedState-test.js
 * should provide up to date values for props
 
-src/renderers/shared/stack/reconciler/__tests__/ReactCompositeComponentState-test.js
-* should support setting state
-
 src/renderers/shared/stack/reconciler/__tests__/ReactEmptyComponent-test.js
 * should still throw when rendering to undefined
 * should be able to switch between rendering null and a normal tag
@@ -565,6 +562,9 @@ src/renderers/shared/stack/reconciler/__tests__/ReactEmptyComponent-test.js
 * throws when rendering null at the top level
 * preserves the dom node during updates
 
+src/renderers/shared/stack/reconciler/__tests__/ReactErrorBoundaries-test.js
+* lets different boundaries catch their own first errors
+
 src/renderers/shared/stack/reconciler/__tests__/ReactMultiChild-test.js
 * should warn for duplicated keys with component stack info
 

scripts/fiber/tests-passing.txt

@@ -1016,6 +1016,7 @@ src/renderers/shared/stack/reconciler/__tests__/ReactCompositeComponentDOMMinima
 * should not render extra nodes for non-interpolated text
 
 src/renderers/shared/stack/reconciler/__tests__/ReactCompositeComponentState-test.js
+* should support setting state
 * should batch unmounts
 
 src/renderers/shared/stack/reconciler/__tests__/ReactEmptyComponent-test.js
@@ -1058,7 +1059,6 @@ src/renderers/shared/stack/reconciler/__tests__/ReactErrorBoundaries-test.js
 * catches errors in componentDidMount
 * catches errors in componentDidUpdate
 * propagates errors inside boundary during componentDidMount
-* lets different boundaries catch their own first errors
 
 src/renderers/shared/stack/reconciler/__tests__/ReactIdentity-test.js
 * should allow key property to express identity

src/renderers/shared/fiber/ReactFiberScheduler.js

@@ -167,7 +167,7 @@ module.exports = function<T, P, I, TI, C>(config : HostConfig<T, P, I, TI, C>) {
           commitInsertion(effectfulFiber);
           // Clear the "placement" from effect tag so that we know that this is inserted, before
           // any life-cycles like componentDidMount gets called.
-          effectfulFiber.effectTag = NoEffect;
+          effectfulFiber.effectTag ^= Placement;
           break;
         }
         case PlacementAndUpdate:
@@ -176,7 +176,7 @@ module.exports = function<T, P, I, TI, C>(config : HostConfig<T, P, I, TI, C>) {
           commitInsertion(effectfulFiber);
           // Clear the "placement" from effect tag so that we know that this is inserted, before
           // any life-cycles like componentDidMount gets called.
-          effectfulFiber.effectTag = Update;
+          effectfulFiber.effectTag ^= Placement;
 
           // Update
           const current = effectfulFiber.alternate;
@@ -250,6 +250,7 @@ module.exports = function<T, P, I, TI, C>(config : HostConfig<T, P, I, TI, C>) {
     if (allTrappedErrors) {
       handleErrors(allTrappedErrors);
     }
+    performTaskWork();
   }
 
   function resetWorkPriority(workInProgress : Fiber) {
@@ -499,9 +500,9 @@ module.exports = function<T, P, I, TI, C>(config : HostConfig<T, P, I, TI, C>) {
     }
   }
 
-  // function performTaskWork() {
-  //   performAndHandleErrors(TaskPriority);
-  // }
+  function performTaskWork() {
+    performAndHandleErrors(TaskPriority);
+  }
 
   function performAndHandleErrors(priorityLevel : PriorityLevel, deadline : null | Deadline) {
     // The exact priority level doesn't matter, so long as it's in range of the
@@ -611,7 +612,14 @@ module.exports = function<T, P, I, TI, C>(config : HostConfig<T, P, I, TI, C>) {
   }
 
   function scheduleWork(root : FiberRoot) {
-    scheduleWorkAtPriority(root, priorityContext);
+    let priorityLevel = priorityContext;
+
+    // If we're in a batch, switch to task priority
+    if (priorityLevel === SynchronousPriority && shouldBatchUpdates) {
+      priorityLevel = TaskPriority;
+    }
+
+    scheduleWorkAtPriority(root, priorityLevel);
   }
 
   function scheduleWorkAtPriority(root : FiberRoot, priorityLevel : PriorityLevel) {
@@ -647,10 +655,8 @@ module.exports = function<T, P, I, TI, C>(config : HostConfig<T, P, I, TI, C>) {
   function scheduleCallbackAtPriority(priorityLevel : PriorityLevel) {
     switch (priorityLevel) {
       case SynchronousPriority:
-        if (!shouldBatchUpdates) {
-          // Unless in batched mode, perform work immediately
-          performSynchronousWork();
-        }
+        // Perform work immediately
+        performSynchronousWork();
         return;
       case TaskPriority:
         // Do nothing. Task work should be flushed after committing.
@@ -667,7 +673,12 @@ module.exports = function<T, P, I, TI, C>(config : HostConfig<T, P, I, TI, C>) {
   }
 
   function scheduleUpdate(fiber : Fiber) {
-    const priorityLevel = priorityContext;
+    let priorityLevel = priorityContext;
+    // If we're in a batch, switch to task priority
+    if (priorityLevel === SynchronousPriority && shouldBatchUpdates) {
+      priorityLevel = TaskPriority;
+    }
+
     while (true) {
       if (fiber.pendingWorkPriority === NoWork ||
           fiber.pendingWorkPriority >= priorityLevel) {
@@ -709,9 +720,9 @@ module.exports = function<T, P, I, TI, C>(config : HostConfig<T, P, I, TI, C>) {
       return fn();
     } finally {
       shouldBatchUpdates = prev;
-      // If we've exited the batch, perform any scheduled sync work
+      // If we've exited the batch, perform any scheduled task work
       if (!shouldBatchUpdates) {
-        performSynchronousWork();
+        performTaskWork();
       }
     }
   }