[Fiber] Swap .child and .stateNode in coroutines

src/renderers/shared/fiber/ReactFiberBeginWork.js

@@ -518,11 +518,49 @@ module.exports = function<T, P, I, TI, PI, C, CX, PL>(
     } else if (nextCoroutine === null || workInProgress.memoizedProps === nextCoroutine) {
       return bailoutOnAlreadyFinishedWork(current, workInProgress);
     }
-    reconcileChildren(current, workInProgress, nextCoroutine.children);
+
+    const nextChildren = nextCoroutine.children;
+    const priorityLevel = workInProgress.pendingWorkPriority;
+
+    // The following is a fork of reconcileChildrenAtPriority but using
+    // stateNode to store the child.
+
+    // At this point any memoization is no longer valid since we'll have changed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);
+    }
+
     memoizeProps(workInProgress, nextCoroutine);
     // 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;
   }
 
   function updatePortalComponent(current, workInProgress) {

src/renderers/shared/fiber/ReactFiberCommitWork.js

@@ -136,7 +136,6 @@ module.exports = function<T, P, I, TI, PI, C, CX, PL>(
       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;
@@ -198,7 +197,6 @@ module.exports = function<T, P, I, TI, PI, C, CX, PL>(
         // 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.child.return = node;
         node = node.child;
         continue;
@@ -229,7 +227,6 @@ module.exports = function<T, P, I, TI, PI, C, CX, PL>(
       // Visit children because they may contain more composite or host nodes.
       // Skip portals because commitUnmount() currently visits them recursively.
       if (node.child && node.tag !== HostPortal) {
-        // TODO: Coroutines need to visit the stateNode.
         node.child.return = node;
         node = node.child;
         continue;
@@ -273,7 +270,6 @@ module.exports = function<T, P, I, TI, PI, C, CX, PL>(
         commitUnmount(node);
         // Visit children because we may find more host components below.
         if (node.child) {
-          // TODO: Coroutines need to visit the stateNode.
           node.child.return = node;
           node = node.child;
           continue;

src/renderers/shared/fiber/ReactFiberCompleteWork.js

@@ -66,22 +66,33 @@ module.exports = function<T, P, I, TI, PI, C, CX, PL>(
     popHostContainer,
   } = hostContext;
 
+  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.
     workInProgress.effectTag |= Update;
   }
 
   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 === HostPortal) {
         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;
@@ -123,16 +134,17 @@ module.exports = function<T, P, I, TI, PI, C, CX, PL>(
     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) {
@@ -147,7 +159,6 @@ module.exports = function<T, P, I, TI, PI, C, CX, PL>(
         // 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

@@ -434,6 +434,8 @@ module.exports = function<T, P, I, TI, PI, C, CX, PL>(config : HostConfig<T, P,
       newPriority = getPendingPriority(queue);
     }
 
+    // TODO: Coroutines need to visit stateNode
+
     // progressedChild is going to be the child set with the highest priority.
     // Either it is the same as child, or it just bailed out because it choose
     // not to do the work.

src/renderers/shared/fiber/ReactFiberTreeReflection.js

@@ -168,7 +168,6 @@ exports.findCurrentHostFiber = function(parent : Fiber) : Fiber | null {
       return node;
     } else if (node.child) {
       // TODO: If we hit a Portal, we're supposed to skip it.
-      // TODO: Coroutines need to visit the stateNode.
       node.child.return = node;
       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',
     ]);
 
   });

src/test/ReactTestUtils.js

@@ -97,7 +97,6 @@ function findAllInRenderedFiberTreeInternal(fiber, test) {
       }
     }
     if (node.child) {
-      // TODO: Coroutines need to visit the stateNode.
       node.child.return = node;
       node = node.child;
       continue;