Merge pull request #6988 from sebmarkbage/newreconciler

[Fiber] Minimize abuse of .alternate
(cherry picked from commit 0cafd83834)

src/renderers/shared/fiber/ReactChildFiber.js

@@ -28,7 +28,7 @@ var {
 var ReactFiber = require('ReactFiber');
 var ReactReifiedYield = require('ReactReifiedYield');
 
-function createSubsequentChild(parent : Fiber, nextReusable : ?Fiber, previousSibling : Fiber, newChildren) : Fiber {
+function createSubsequentChild(parent : Fiber, existingChild : ?Fiber, previousSibling : Fiber, newChildren) : Fiber {
   if (typeof newChildren !== 'object' || newChildren === null) {
     return previousSibling;
   }
@@ -36,14 +36,14 @@ function createSubsequentChild(parent : Fiber, nextReusable : ?Fiber, previousSi
   switch (newChildren.$$typeof) {
     case REACT_ELEMENT_TYPE: {
       const element = (newChildren : ReactElement<any>);
-      if (nextReusable &&
-          element.type === nextReusable.type &&
-          element.key === nextReusable.key) {
+      if (existingChild &&
+          element.type === existingChild.type &&
+          element.key === existingChild.key) {
         // TODO: This is not sufficient since previous siblings could be new.
         // Will fix reconciliation properly later.
-        const clone = ReactFiber.cloneFiber(nextReusable);
+        const clone = ReactFiber.cloneFiber(existingChild);
         clone.input = element.props;
-        clone.child = nextReusable.child;
+        clone.child = existingChild.child;
         clone.sibling = null;
         previousSibling.sibling = clone;
         return clone;
@@ -75,12 +75,14 @@ function createSubsequentChild(parent : Fiber, nextReusable : ?Fiber, previousSi
 
   if (Array.isArray(newChildren)) {
     let prev : Fiber = previousSibling;
+    let existing : ?Fiber = existingChild;
     for (var i = 0; i < newChildren.length; i++) {
-      let reusable = null;
-      if (prev.alternate) {
-        reusable = prev.alternate.sibling;
+      prev = createSubsequentChild(parent, existing, prev, newChildren[i]);
+      if (prev && existing) {
+        // TODO: This is not correct because there could've been more
+        // than one sibling consumed but I don't want to return a tuple.
+        existing = existing.sibling;
       }
-      prev = createSubsequentChild(parent, reusable, prev, newChildren[i]);
     }
     return prev;
   } else {
@@ -89,7 +91,7 @@ function createSubsequentChild(parent : Fiber, nextReusable : ?Fiber, previousSi
   }
 }
 
-function createFirstChild(parent, newChildren) {
+function createFirstChild(parent, existingChild, newChildren) {
   if (typeof newChildren !== 'object' || newChildren === null) {
     return null;
   }
@@ -97,7 +99,6 @@ function createFirstChild(parent, newChildren) {
   switch (newChildren.$$typeof) {
     case REACT_ELEMENT_TYPE: {
       const element = (newChildren : ReactElement<any>);
-      const existingChild : ?Fiber = parent.child;
       if (existingChild &&
           element.type === existingChild.type &&
           element.key === existingChild.key) {
@@ -136,16 +137,18 @@ function createFirstChild(parent, newChildren) {
   if (Array.isArray(newChildren)) {
     var first : ?Fiber = null;
     var prev : ?Fiber = null;
+    var existing : ?Fiber = existingChild;
     for (var i = 0; i < newChildren.length; i++) {
       if (prev == null) {
-        prev = createFirstChild(parent, newChildren[i]);
+        prev = createFirstChild(parent, existing, newChildren[i]);
         first = prev;
       } else {
-        let reusable = null;
-        if (prev.alternate) {
-          reusable = prev.alternate.sibling;
-        }
-        prev = createSubsequentChild(parent, reusable, prev, newChildren[i]);
+        prev = createSubsequentChild(parent, existing, prev, newChildren[i]);
+      }
+      if (prev && existing) {
+        // TODO: This is not correct because there could've been more
+        // than one sibling consumed but I don't want to return a tuple.
+        existing = existing.sibling;
       }
     }
     return first;
@@ -155,6 +158,6 @@ function createFirstChild(parent, newChildren) {
   }
 }
 
-exports.reconcileChildFibers = function(parent : Fiber, firstChild : ?Fiber, newChildren : ReactNodeList) : ?Fiber {
-  return createFirstChild(parent, newChildren);
+exports.reconcileChildFibers = function(parent : Fiber, currentFirstChild : ?Fiber, newChildren : ReactNodeList) : ?Fiber {
+  return createFirstChild(parent, currentFirstChild, newChildren);
 };

src/renderers/shared/fiber/ReactFiberBeginWork.js

@@ -27,31 +27,30 @@ var {
   YieldComponent,
 } = ReactTypesOfWork;
 
-function updateFunctionalComponent(workInProgress) {
+function reconcileChildren(current, workInProgress, nextChildren) {
+  workInProgress.child = ReactChildFiber.reconcileChildFibers(
+    workInProgress,
+    current ? current.child : null,
+    nextChildren
+  );
+}
+
+function updateFunctionalComponent(current, workInProgress) {
   var fn = workInProgress.type;
   var props = workInProgress.input;
   console.log('update fn:', fn.name);
   var nextChildren = fn(props);
-
-  workInProgress.child = ReactChildFiber.reconcileChildFibers(
-    workInProgress,
-    workInProgress.child,
-    nextChildren
-  );
+  reconcileChildren(current, workInProgress, nextChildren);
 }
 
-function updateHostComponent(workInProgress) {
+function updateHostComponent(current, workInProgress) {
   console.log('host component', workInProgress.type, typeof workInProgress.input.children === 'string' ? workInProgress.input.children : '');
 
   var nextChildren = workInProgress.input.children;
-  workInProgress.child = ReactChildFiber.reconcileChildFibers(
-    workInProgress,
-    workInProgress.child,
-    nextChildren
-  );
+  reconcileChildren(current, workInProgress, nextChildren);
 }
 
-function mountIndeterminateComponent(workInProgress) {
+function mountIndeterminateComponent(current, workInProgress) {
   var fn = workInProgress.type;
   var props = workInProgress.input;
   var value = fn(props);
@@ -64,34 +63,30 @@ function mountIndeterminateComponent(workInProgress) {
     // Proceed under the assumption that this is a functional component
     workInProgress.tag = FunctionalComponent;
   }
-  workInProgress.child = ReactChildFiber.reconcileChildFibers(
-    workInProgress,
-    workInProgress.child,
-    value
-  );
+  reconcileChildren(current, workInProgress, value);
 }
 
-function updateCoroutineComponent(workInProgress) {
+function updateCoroutineComponent(current, workInProgress) {
   var coroutine = (workInProgress.input : ?ReactCoroutine);
   if (!coroutine) {
     throw new Error('Should be resolved by now');
   }
   console.log('begin coroutine', workInProgress.type.name);
-  workInProgress.child = ReactChildFiber.reconcileChildFibers(
-    workInProgress,
-    workInProgress.child,
-    coroutine.children
-  );
+  reconcileChildren(current, workInProgress, coroutine.children);
 }
 
-function beginWork(workInProgress : Fiber) : ?Fiber {
-  const alt = workInProgress.alternate;
-  if (alt && workInProgress.input === alt.memoizedInput) {
+function beginWork(current : ?Fiber, workInProgress : Fiber) : ?Fiber {
+  // The current, flushed, state of this fiber is the alternate.
+  // Ideally nothing should rely on this, but relying on it here
+  // means that we don't need an additional field on the work in
+  // progress.
+  if (current && workInProgress.input === current.memoizedInput) {
     // The most likely scenario is that the previous copy of the tree contains
     // the same input as the new one. In that case, we can just copy the output
     // and children from that node.
-    workInProgress.output = alt.output;
-    workInProgress.child = alt.child;
+    workInProgress.output = current.output;
+    workInProgress.child = current.child;
+    workInProgress.stateNode = current.stateNode;
     return null;
   }
   if (workInProgress.input === workInProgress.memoizedInput) {
@@ -101,40 +96,45 @@ function beginWork(workInProgress : Fiber) : ?Fiber {
   }
   switch (workInProgress.tag) {
     case IndeterminateComponent:
-      mountIndeterminateComponent(workInProgress);
-      break;
+      mountIndeterminateComponent(current, workInProgress);
+      return workInProgress.child;
     case FunctionalComponent:
-      updateFunctionalComponent(workInProgress);
-      break;
+      updateFunctionalComponent(current, workInProgress);
+      return workInProgress.child;
     case ClassComponent:
       console.log('class component', workInProgress.input.type.name);
-      break;
+      return workInProgress.child;
     case HostComponent:
-      updateHostComponent(workInProgress);
-      break;
+      updateHostComponent(current, workInProgress);
+      return workInProgress.child;
     case CoroutineHandlerPhase:
       // This is a restart. Reset the tag to the initial phase.
       workInProgress.tag = CoroutineComponent;
       // Intentionally fall through since this is now the same.
     case CoroutineComponent:
-      updateCoroutineComponent(workInProgress);
+      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.
       if (workInProgress.child) {
-        return beginWork(workInProgress.child);
+        return beginWork(
+          workInProgress.child.alternate,
+          workInProgress.child
+        );
       }
-      break;
+      return workInProgress.child;
     case YieldComponent:
       // A yield component is just a placeholder, we can just run through the
       // next one immediately.
       if (workInProgress.sibling) {
-        return beginWork(workInProgress.sibling);
+        return beginWork(
+          workInProgress.sibling.alternate,
+          workInProgress.sibling
+        );
       }
       return null;
     default:
       throw new Error('Unknown unit of work tag');
   }
-  return workInProgress.child;
 }
 
 exports.beginWork = beginWork;

src/renderers/shared/fiber/ReactFiberCompleteWork.js

@@ -54,7 +54,7 @@ function recursivelyFillYields(yields, output : ?Fiber | ?ReifiedYield) {
   }
 }
 
-function moveCoroutineToHandlerPhase(workInProgress : Fiber) {
+function moveCoroutineToHandlerPhase(current : ?Fiber, workInProgress : Fiber) {
   var coroutine = (workInProgress.input : ?ReactCoroutine);
   if (!coroutine) {
     throw new Error('Should be resolved by now');
@@ -81,15 +81,16 @@ function moveCoroutineToHandlerPhase(workInProgress : Fiber) {
   var props = coroutine.props;
   var nextChildren = fn(props, yields);
 
+  var currentFirstChild = current ? current.stateNode : null;
   workInProgress.stateNode = ReactChildFiber.reconcileChildFibers(
     workInProgress,
-    workInProgress.stateNode,
+    currentFirstChild,
     nextChildren
   );
   return workInProgress.stateNode;
 }
 
-exports.completeWork = function(workInProgress : Fiber) : ?Fiber {
+exports.completeWork = function(current : ?Fiber, workInProgress : Fiber) : ?Fiber {
   switch (workInProgress.tag) {
     case FunctionalComponent:
       console.log('/functional component', workInProgress.type.name);
@@ -104,7 +105,7 @@ exports.completeWork = function(workInProgress : Fiber) : ?Fiber {
       break;
     case CoroutineComponent:
       console.log('/coroutine component', workInProgress.input.handler.name);
-      return moveCoroutineToHandlerPhase(workInProgress);
+      return moveCoroutineToHandlerPhase(current, workInProgress);
     case CoroutineHandlerPhase:
       transferOutput(workInProgress.stateNode, workInProgress);
       // Reset the tag to now be a first phase coroutine.

src/renderers/shared/fiber/ReactFiberReconciler.js

@@ -51,7 +51,12 @@ module.exports = function<T, P, I>(config : HostConfig<T, P, I>) : Reconciler {
 
   function completeUnitOfWork(workInProgress : Fiber) : ?Fiber {
     while (true) {
-      var next = completeWork(workInProgress);
+      // The current, flushed, state of this fiber is the alternate.
+      // Ideally nothing should rely on this, but relying on it here
+      // means that we don't need an additional field on the work in
+      // progress.
+      const current = workInProgress.alternate;
+      const next = completeWork(current, workInProgress);
       if (next) {
         // If completing this work spawned new work, do that next.
         return next;
@@ -74,7 +79,12 @@ module.exports = function<T, P, I>(config : HostConfig<T, P, I>) : Reconciler {
   }
 
   function performUnitOfWork(workInProgress : Fiber) : ?Fiber {
-    var next = beginWork(workInProgress);
+    // The current, flushed, state of this fiber is the alternate.
+    // Ideally nothing should rely on this, but relying on it here
+    // means that we don't need an additional field on the work in
+    // progress.
+    const current = workInProgress.alternate;
+    const next = beginWork(current, workInProgress);
     if (next) {
       // If this spawns new work, do that next.
       return next;
@@ -123,8 +133,8 @@ module.exports = function<T, P, I>(config : HostConfig<T, P, I>) : Reconciler {
       // TODO: Unify this with ReactChildFiber. We can't now because the parent
       // is passed. Should be doable though. Might require a wrapper don't know.
       if (rootFiber && rootFiber.type === element.type && rootFiber.key === element.key) {
-        nextUnitOfWork = rootFiber;
-        rootFiber.input = element.props;
+        nextUnitOfWork = ReactFiber.cloneFiber(rootFiber);
+        nextUnitOfWork.input = element.props;
         return {};
       }