Initial hooks implementation

Includes:
- useState
- useContext
- useEffect
- useRef
- useReducer
- useCallback
- useMemo
- useAPI

packages/react-reconciler/src/ReactFiberBeginWork.js

@@ -79,6 +79,7 @@ import {
   prepareToReadContext,
   calculateChangedBits,
 } from './ReactFiberNewContext';
+import {prepareToUseHooks, finishHooks, resetHooks} from './ReactFiberHooks';
 import {stopProfilerTimerIfRunning} from './ReactProfilerTimer';
 import {
   getMaskedContext,
@@ -193,27 +194,17 @@ function forceUnmountCurrentAndReconcile(
 function updateForwardRef(
   current: Fiber | null,
   workInProgress: Fiber,
-  type: any,
+  Component: any,
   nextProps: any,
   renderExpirationTime: ExpirationTime,
 ) {
-  const render = type.render;
+  const render = Component.render;
   const ref = workInProgress.ref;
-  if (hasLegacyContextChanged()) {
-    // Normally we can bail out on props equality but if context has changed
-    // we don't do the bailout and we have to reuse existing props instead.
-  } else if (workInProgress.memoizedProps === nextProps) {
-    const currentRef = current !== null ? current.ref : null;
-    if (ref === currentRef) {
-      return bailoutOnAlreadyFinishedWork(
-        current,
-        workInProgress,
-        renderExpirationTime,
-      );
-    }
-  }
 
+  // The rest is a fork of updateFunctionComponent
   let nextChildren;
+  prepareToReadContext(workInProgress, renderExpirationTime);
+  prepareToUseHooks(current, workInProgress, renderExpirationTime);
   if (__DEV__) {
     ReactCurrentOwner.current = workInProgress;
     ReactCurrentFiber.setCurrentPhase('render');
@@ -222,7 +213,10 @@ function updateForwardRef(
   } else {
     nextChildren = render(nextProps, ref);
   }
+  nextChildren = finishHooks(render, nextProps, nextChildren, ref);
 
+  // React DevTools reads this flag.
+  workInProgress.effectTag |= PerformedWork;
   reconcileChildren(
     current,
     workInProgress,
@@ -406,6 +400,7 @@ function updateFunctionComponent(
 
   let nextChildren;
   prepareToReadContext(workInProgress, renderExpirationTime);
+  prepareToUseHooks(current, workInProgress, renderExpirationTime);
   if (__DEV__) {
     ReactCurrentOwner.current = workInProgress;
     ReactCurrentFiber.setCurrentPhase('render');
@@ -414,6 +409,7 @@ function updateFunctionComponent(
   } else {
     nextChildren = Component(nextProps, context);
   }
+  nextChildren = finishHooks(Component, nextProps, nextChildren, context);
 
   // React DevTools reads this flag.
   workInProgress.effectTag |= PerformedWork;
@@ -921,6 +917,7 @@ function mountIndeterminateComponent(
   const context = getMaskedContext(workInProgress, unmaskedContext);
 
   prepareToReadContext(workInProgress, renderExpirationTime);
+  prepareToUseHooks(null, workInProgress, renderExpirationTime);
 
   let value;
 
@@ -964,6 +961,9 @@ function mountIndeterminateComponent(
     // Proceed under the assumption that this is a class instance
     workInProgress.tag = ClassComponent;
 
+    // Throw out any hooks that were used.
+    resetHooks();
+
     // Push context providers early to prevent context stack mismatches.
     // During mounting we don't know the child context yet as the instance doesn't exist.
     // We will invalidate the child context in finishClassComponent() right after rendering.
@@ -1001,6 +1001,7 @@ function mountIndeterminateComponent(
   } else {
     // Proceed under the assumption that this is a function component
     workInProgress.tag = FunctionComponent;
+    value = finishHooks(Component, props, value, context);
     if (__DEV__) {
       if (Component) {
         warningWithoutStack(

packages/react-reconciler/src/ReactFiberCommitWork.js

@@ -19,12 +19,15 @@ import type {FiberRoot} from './ReactFiberRoot';
 import type {ExpirationTime} from './ReactFiberExpirationTime';
 import type {CapturedValue, CapturedError} from './ReactCapturedValue';
 import type {SuspenseState} from './ReactFiberSuspenseComponent';
+import type {FunctionComponentUpdateQueue} from './ReactFiberHooks';
 
 import {
   enableSchedulerTracing,
   enableProfilerTimer,
 } from 'shared/ReactFeatureFlags';
 import {
+  FunctionComponent,
+  ForwardRef,
   ClassComponent,
   HostRoot,
   HostComponent,
@@ -180,6 +183,22 @@ function safelyDetachRef(current: Fiber) {
   }
 }
 
+function safelyCallDestroy(current, destroy) {
+  if (__DEV__) {
+    invokeGuardedCallback(null, destroy, null);
+    if (hasCaughtError()) {
+      const error = clearCaughtError();
+      captureCommitPhaseError(current, error);
+    }
+  } else {
+    try {
+      destroy();
+    } catch (error) {
+      captureCommitPhaseError(current, error);
+    }
+  }
+}
+
 function commitBeforeMutationLifeCycles(
   current: Fiber | null,
   finishedWork: Fiber,
@@ -235,13 +254,145 @@ function commitBeforeMutationLifeCycles(
   }
 }
 
+function destroyRemainingEffects(firstToDestroy, stopAt) {
+  let effect = firstToDestroy;
+  do {
+    const destroy = effect.value;
+    if (destroy !== null) {
+      destroy();
+    }
+    effect = effect.next;
+  } while (effect !== stopAt);
+}
+
+function destroyMountedEffects(current) {
+  const oldUpdateQueue: FunctionComponentUpdateQueue | null = (current.updateQueue: any);
+  if (oldUpdateQueue !== null) {
+    const oldLastEffect = oldUpdateQueue.lastEffect;
+    if (oldLastEffect !== null) {
+      const oldFirstEffect = oldLastEffect.next;
+      destroyRemainingEffects(oldFirstEffect, oldFirstEffect);
+    }
+  }
+}
+
 function commitLifeCycles(
   finishedRoot: FiberRoot,
   current: Fiber | null,
   finishedWork: Fiber,
   committedExpirationTime: ExpirationTime,
 ): void {
   switch (finishedWork.tag) {
+    case FunctionComponent:
+    case ForwardRef: {
+      const updateQueue: FunctionComponentUpdateQueue | null = (finishedWork.updateQueue: any);
+      if (updateQueue !== null) {
+        // Mount new effects and destroy the old ones by comparing to the
+        // current list of effects. This could be a bit simpler if we avoided
+        // the need to compare to the previous effect list by transferring the
+        // old `destroy` method to the new effect during the render phase.
+        // That's how I originally implemented it, but it requires an additional
+        // field on the effect object.
+        //
+        // This supports removing effects from the end of the list. If we adopt
+        // the constraint that hooks are append only, that would also save a bit
+        // on code size.
+        const newLastEffect = updateQueue.lastEffect;
+        if (newLastEffect !== null) {
+          const newFirstEffect = newLastEffect.next;
+          let oldLastEffect = null;
+          if (current !== null) {
+            const oldUpdateQueue: FunctionComponentUpdateQueue | null = (current.updateQueue: any);
+            if (oldUpdateQueue !== null) {
+              oldLastEffect = oldUpdateQueue.lastEffect;
+            }
+          }
+          if (oldLastEffect !== null) {
+            const oldFirstEffect = oldLastEffect.next;
+            let newEffect = newFirstEffect;
+            let oldEffect = oldFirstEffect;
+
+            // Before mounting the new effects, unmount all the old ones.
+            do {
+              if (oldEffect !== null) {
+                if (newEffect.inputs !== oldEffect.inputs) {
+                  const destroy = oldEffect.value;
+                  if (destroy !== null) {
+                    destroy();
+                  }
+                }
+                oldEffect = oldEffect.next;
+                if (oldEffect === oldFirstEffect) {
+                  oldEffect = null;
+                }
+              }
+              newEffect = newEffect.next;
+            } while (newEffect !== newFirstEffect);
+
+            // Unmount any remaining effects in the old list that do not
+            // appear in the new one.
+            if (oldEffect !== null) {
+              destroyRemainingEffects(oldEffect, oldFirstEffect);
+            }
+
+            // Now loop through the list again to mount the new effects
+            oldEffect = oldFirstEffect;
+            do {
+              const create = newEffect.value;
+              if (oldEffect !== null) {
+                if (newEffect.inputs !== oldEffect.inputs) {
+                  const newDestroy = create();
+                  newEffect.value =
+                    typeof newDestroy === 'function' ? newDestroy : null;
+                } else {
+                  newEffect.value = oldEffect.value;
+                }
+                oldEffect = oldEffect.next;
+                if (oldEffect === oldFirstEffect) {
+                  oldEffect = null;
+                }
+              } else {
+                const newDestroy = create();
+                newEffect.value =
+                  typeof newDestroy === 'function' ? newDestroy : null;
+              }
+              newEffect = newEffect.next;
+            } while (newEffect !== newFirstEffect);
+          } else {
+            let newEffect = newFirstEffect;
+            do {
+              const create = newEffect.value;
+              const newDestroy = create();
+              newEffect.value =
+                typeof newDestroy === 'function' ? newDestroy : null;
+              newEffect = newEffect.next;
+            } while (newEffect !== newFirstEffect);
+          }
+        } else if (current !== null) {
+          // There are no effects, which means all current effects must
+          // be destroyed
+          destroyMountedEffects(current);
+        }
+
+        const callbackList = updateQueue.callbackList;
+        if (callbackList !== null) {
+          updateQueue.callbackList = null;
+          for (let i = 0; i < callbackList.length; i++) {
+            const update = callbackList[i];
+            // Assume this is non-null, since otherwise it would not be part
+            // of the callback list.
+            const callback: () => mixed = (update.callback: any);
+            update.callback = null;
+            callback();
+          }
+        }
+      } else if (current !== null) {
+        // There are no effects, which means all current effects must
+        // be destroyed
+        destroyMountedEffects(current);
+      }
+      break;
+    }
     case ClassComponent: {
       const instance = finishedWork.stateNode;
       if (finishedWork.effectTag & Update) {
@@ -496,6 +647,25 @@ function commitUnmount(current: Fiber): void {
   onCommitUnmount(current);
 
   switch (current.tag) {
+    case FunctionComponent:
+    case ForwardRef: {
+      const updateQueue: FunctionComponentUpdateQueue | null = (current.updateQueue: any);
+      if (updateQueue !== null) {
+        const lastEffect = updateQueue.lastEffect;
+        if (lastEffect !== null) {
+          const firstEffect = lastEffect.next;
+          let effect = firstEffect;
+          do {
+            const destroy = effect.value;
+            if (destroy !== null) {
+              safelyCallDestroy(current, destroy);
+            }
+            effect = effect.next;
+          } while (effect !== firstEffect);
+        }
+      }
+      break;
+    }
     case ClassComponent: {
       safelyDetachRef(current);
       const instance = current.stateNode;

packages/react-reconciler/src/ReactFiberDispatcher.js

@@ -8,7 +8,23 @@
  */
 
 import {readContext} from './ReactFiberNewContext';
+import {
+  useState,
+  useReducer,
+  useEffect,
+  useCallback,
+  useMemo,
+  useRef,
+  useAPI,
+} from './ReactFiberHooks';
 
 export const Dispatcher = {
   readContext,
+  useState,
+  useReducer,
+  useEffect,
+  useCallback,
+  useMemo,
+  useRef,
+  useAPI,
 };