Swap .child and .stateNode in coroutines

It is slightly more useful this way because when we want to find host nodes
we typically want to do so in the second phase. That's the real tree where
as the first phase is more of a virtual part of the tree.

Author: sebmarkbage

src/renderers/shared/fiber/ReactFiberBeginWork.js

@@ -296,7 +296,41 @@ module.exports = function<T, P, I, TI, C>(
     if (!coroutine) {
       throw new Error('Should be resolved by now');
     }
-    reconcileChildren(current, workInProgress, coroutine.children);
+
+    const nextChildren = coroutine.children;
+    const priorityLevel = workInProgress.pendingWorkPriority;
+    // At this point any memoization is no longer valid since we'll have changed
+    // the children.
+    workInProgress.memoizedProps = null;
+    if (!current) {
+      workInProgress.stateNode = mountChildFibersInPlace(
+        workInProgress,
+        workInProgress.stateNode,
+        nextChildren,
+        priorityLevel
+      );
+    } else if (current.child === workInProgress.child) {
+      clearDeletions(workInProgress);
+
+      workInProgress.stateNode = reconcileChildFibers(
+        workInProgress,
+        workInProgress.stateNode,
+        nextChildren,
+        priorityLevel
+      );
+
+      transferDeletions(workInProgress);
+    } else {
+      workInProgress.stateNode = reconcileChildFibersInPlace(
+        workInProgress,
+        workInProgress.stateNode,
+        nextChildren,
+        priorityLevel
+      );
+
+      transferDeletions(workInProgress);
+    }
+    // markChildAsProgressed(current, workInProgress, priorityLevel);
   }
 
   function updatePortalComponent(current, workInProgress) {
@@ -462,9 +496,7 @@ module.exports = function<T, P, I, TI, C>(
         // Intentionally fall through since this is now the same.
       case CoroutineComponent:
         updateCoroutineComponent(current, workInProgress);
-        // This doesn't take arbitrary time so we could synchronously just begin
-        // eagerly do the work of workInProgress.child as an optimization.
-        return workInProgress.child;
+        return workInProgress.stateNode;
       case YieldComponent:
         // A yield component is just a placeholder, we can just run through the
         // next one immediately.

src/renderers/shared/fiber/ReactFiberCommitWork.js

@@ -112,7 +112,6 @@ module.exports = function<T, P, I, TI, C>(
       while (node.tag !== HostComponent && node.tag !== HostText) {
         // If it is not host node and, we might have a host node inside it.
         // Try to search down until we find one.
-        // TODO: For coroutines, this will have to search the stateNode.
         if (node.effectTag & Placement) {
           // If we don't have a child, try the siblings instead.
           continue siblings;
@@ -151,7 +150,6 @@ module.exports = function<T, P, I, TI, C>(
         // down its children. Instead, we'll get insertions from each child in
         // the portal directly.
       } else if (node.child) {
-        // TODO: Coroutines need to visit the stateNode.
         node = node.child;
         continue;
       }
@@ -178,7 +176,6 @@ module.exports = function<T, P, I, TI, C>(
     while (true) {
       commitUnmount(node);
       if (node.child) {
-        // TODO: Coroutines need to visit the stateNode.
         node.child.return = node;
         node = node.child;
         continue;
@@ -218,7 +215,6 @@ module.exports = function<T, P, I, TI, C>(
       } else {
         commitUnmount(node);
         if (node.child) {
-          // TODO: Coroutines need to visit the stateNode.
           node.child.return = node;
           node = node.child;
           continue;

src/renderers/shared/fiber/ReactFiberCompleteWork.js

@@ -51,6 +51,18 @@ module.exports = function<T, P, I, TI, C>(config : HostConfig<T, P, I, TI, C>) {
   const createTextInstance = config.createTextInstance;
   const prepareUpdate = config.prepareUpdate;
 
+  function markChildAsProgressed(current, workInProgress, priorityLevel) {
+    // We now have clones. Let's store them as the currently progressed work.
+    workInProgress.progressedChild = workInProgress.child;
+    workInProgress.progressedPriority = priorityLevel;
+    if (current) {
+      // We also store it on the current. When the alternate swaps in we can
+      // continue from this point.
+      current.progressedChild = workInProgress.progressedChild;
+      current.progressedPriority = workInProgress.progressedPriority;
+    }
+  }
+
   function markUpdate(workInProgress : Fiber) {
     // Tag the fiber with an update effect. This turns a Placement into
     // an UpdateAndPlacement.
@@ -63,15 +75,14 @@ module.exports = function<T, P, I, TI, C>(config : HostConfig<T, P, I, TI, C>) {
   }
 
   function appendAllYields(yields : Array<ReifiedYield>, workInProgress : Fiber) {
-    let node = workInProgress.child;
+    let node = workInProgress.stateNode;
     while (node) {
       if (node.tag === HostComponent || node.tag === HostText ||
           node.tag === Portal) {
         throw new Error('A coroutine cannot have host component children.');
       } else if (node.tag === YieldComponent) {
         yields.push(node.type);
       } else if (node.child) {
-        // TODO: Coroutines need to visit the stateNode.
         node.child.return = node;
         node = node.child;
         continue;
@@ -113,16 +124,17 @@ module.exports = function<T, P, I, TI, C>(config : HostConfig<T, P, I, TI, C>) {
     var props = coroutine.props;
     var nextChildren = fn(props, yields);
 
-    var currentFirstChild = current ? current.stateNode : null;
+    var currentFirstChild = current ? current.child : null;
     // Inherit the priority of the returnFiber.
     const priority = workInProgress.pendingWorkPriority;
-    workInProgress.stateNode = reconcileChildFibers(
+    workInProgress.child = reconcileChildFibers(
       workInProgress,
       currentFirstChild,
       nextChildren,
       priority
     );
-    return workInProgress.stateNode;
+    markChildAsProgressed(current, workInProgress, priority);
+    return workInProgress.child;
   }
 
   function appendAllChildren(parent : I, workInProgress : Fiber) {
@@ -137,7 +149,6 @@ module.exports = function<T, P, I, TI, C>(config : HostConfig<T, P, I, TI, C>) {
         // down its children. Instead, we'll get insertions from each child in
         // the portal directly.
       } else if (node.child) {
-        // TODO: Coroutines need to visit the stateNode.
         node = node.child;
         continue;
       }

src/renderers/shared/fiber/ReactFiberScheduler.js

@@ -294,7 +294,7 @@ module.exports = function<T, P, I, TI, C>(config : HostConfig<T, P, I, TI, C>) {
 
       const returnFiber = workInProgress.return;
 
-      if (returnFiber) {
+      if (returnFiber && !next) {
         // Append all the effects of the subtree and this fiber onto the effect
         // list of the parent. The completion order of the children affects the
         // side-effect order.

src/renderers/shared/fiber/ReactFiberTreeReflection.js

@@ -112,7 +112,6 @@ exports.findCurrentHostFiber = function(parent : Fiber) : Fiber | null {
     if (node.tag === HostComponent || node.tag === HostText) {
       return node;
     } else if (node.child) {
-      // TODO: Coroutines need to visit the stateNode.
       node = node.child;
       continue;
     }

src/renderers/shared/fiber/__tests__/ReactCoroutine-test.js

@@ -143,10 +143,8 @@ describe('ReactCoroutine', () => {
 
     expect(ops).toEqual([
       'Unmount Parent',
-      // TODO: This should happen in the order Child, Continuation which it
-      // will once we swap stateNode and child positions of these.
-      'Unmount Continuation',
       'Unmount Child',
+      'Unmount Continuation',
     ]);
 
   });