React源码学习进阶（七）挂载阶段的commitWork

function performSyncWorkOnRoot(root) {
  // Check if there's expired work on this root. Otherwise, render at Sync.
  const lastExpiredTime = root.lastExpiredTime;
  const expirationTime = lastExpiredTime !== NoWork ? lastExpiredTime : Sync;
  invariant(
    (executionContext & (RenderContext | CommitContext)) === NoContext,
    'Should not already be working.',
  );

  flushPassiveEffects();

  // If the root or expiration time have changed, throw out the existing stack
  // and prepare a fresh one. Otherwise we'll continue where we left off.
  if (root !== workInProgressRoot || expirationTime !== renderExpirationTime) {
    prepareFreshStack(root, expirationTime);
    startWorkOnPendingInteractions(root, expirationTime);
  }

  // If we have a work-in-progress fiber, it means there's still work to do
  // in this root.
  if (workInProgress !== null) {
    const prevExecutionContext = executionContext;
    executionContext |= RenderContext;
    const prevDispatcher = pushDispatcher(root);
    const prevInteractions = pushInteractions(root);
    startWorkLoopTimer(workInProgress);

    do {
      try {
        workLoopSync();
        break;
      } catch (thrownValue) {
        handleError(root, thrownValue);
      }
    } while (true);
    resetContextDependencies();
    executionContext = prevExecutionContext;
    popDispatcher(prevDispatcher);
    if (enableSchedulerTracing) {
      popInteractions(((prevInteractions: any): Set<Interaction>));
    }

    if (workInProgressRootExitStatus === RootFatalErrored) {
      const fatalError = workInProgressRootFatalError;
      stopInterruptedWorkLoopTimer();
      prepareFreshStack(root, expirationTime);
      markRootSuspendedAtTime(root, expirationTime);
      ensureRootIsScheduled(root);
      throw fatalError;
    }

    if (workInProgress !== null) {
      // This is a sync render, so we should have finished the whole tree.
      invariant(
        false,
        'Cannot commit an incomplete root. This error is likely caused by a ' +
          'bug in React. Please file an issue.',
      );
    } else {
      // We now have a consistent tree. Because this is a sync render, we
      // will commit it even if something suspended.
      stopFinishedWorkLoopTimer();
      root.finishedWork = (root.current.alternate: any);
      root.finishedExpirationTime = expirationTime;
      finishSyncRender(root);
    }

    // Before exiting, make sure there's a callback scheduled for the next
    // pending level.
    ensureRootIsScheduled(root);
  }

  return null;
}

function finishSyncRender(root) {
  // Set this to null to indicate there's no in-progress render.
  workInProgressRoot = null;
  commitRoot(root);
}

function commitRoot(root) {
  const renderPriorityLevel = getCurrentPriorityLevel();
  runWithPriority(
    ImmediatePriority,
    commitRootImpl.bind(null, root, renderPriorityLevel),
  );
  return null;
}

function commitRootImpl(root, renderPriorityLevel) {

  const finishedWork = root.finishedWork;
  const expirationTime = root.finishedExpirationTime;
  if (finishedWork === null) {
    return null;
  }
  root.finishedWork = null;
  root.finishedExpirationTime = NoWork;

  // commitRoot never returns a continuation; it always finishes synchronously.
  // So we can clear these now to allow a new callback to be scheduled.
  root.callbackNode = null;
  root.callbackExpirationTime = NoWork;
  root.callbackPriority = NoPriority;
  root.nextKnownPendingLevel = NoWork;

  // Get the list of effects.
  let firstEffect;
  if (finishedWork.effectTag > PerformedWork) {
    // A fiber's effect list consists only of its children, not itself. So if
    // the root has an effect, we need to add it to the end of the list. The
    // resulting list is the set that would belong to the root's parent, if it
    // had one; that is, all the effects in the tree including the root.
    if (finishedWork.lastEffect !== null) {
      finishedWork.lastEffect.nextEffect = finishedWork;
      firstEffect = finishedWork.firstEffect;
    } else {
      firstEffect = finishedWork;
    }
  } else {
    // There is no effect on the root.
    firstEffect = finishedWork.firstEffect;
  }

  if (firstEffect !== null) {
    const prevExecutionContext = executionContext;
    executionContext |= CommitContext;
    const prevInteractions = pushInteractions(root);

    // Reset this to null before calling lifecycles
    ReactCurrentOwner.current = null;

    // The commit phase is broken into several sub-phases. We do a separate pass
    // of the effect list for each phase: all mutation effects come before all
    // layout effects, and so on.

    // The first phase a "before mutation" phase. We use this phase to read the
    // state of the host tree right before we mutate it. This is where
    // getSnapshotBeforeUpdate is called.
    startCommitSnapshotEffectsTimer();
    prepareForCommit(root.containerInfo);
    nextEffect = firstEffect;
    do {
      if (__DEV__) {
        invokeGuardedCallback(null, commitBeforeMutationEffects, null);
        if (hasCaughtError()) {
          invariant(nextEffect !== null, 'Should be working on an effect.');
          const error = clearCaughtError();
          captureCommitPhaseError(nextEffect, error);
          nextEffect = nextEffect.nextEffect;
        }
      } else {
        try {
          commitBeforeMutationEffects();
        } catch (error) {
          invariant(nextEffect !== null, 'Should be working on an effect.');
          captureCommitPhaseError(nextEffect, error);
          nextEffect = nextEffect.nextEffect;
        }
      }
    } while (nextEffect !== null);

    nextEffect = firstEffect;
    do {
      if (__DEV__) {
        invokeGuardedCallback(
          null,
          commitMutationEffects,
          null,
          root,
          renderPriorityLevel,
        );
        if (hasCaughtError()) {
          invariant(nextEffect !== null, 'Should be working on an effect.');
          const error = clearCaughtError();
          captureCommitPhaseError(nextEffect, error);
          nextEffect = nextEffect.nextEffect;
        }
      } else {
        try {
          commitMutationEffects(root, renderPriorityLevel);
        } catch (error) {
          invariant(nextEffect !== null, 'Should be working on an effect.');
          captureCommitPhaseError(nextEffect, error);
          nextEffect = nextEffect.nextEffect;
        }
      }
    } while (nextEffect !== null);
    
    resetAfterCommit(root.containerInfo);

    // The work-in-progress tree is now the current tree. This must come after
    // the mutation phase, so that the previous tree is still current during
    // componentWillUnmount, but before the layout phase, so that the finished
    // work is current during componentDidMount/Update.
    root.current = finishedWork;

    nextEffect = firstEffect;
    do {
      if (__DEV__) {
        invokeGuardedCallback(
          null,
          commitLayoutEffects,
          null,
          root,
          expirationTime,
        );
        if (hasCaughtError()) {
          invariant(nextEffect !== null, 'Should be working on an effect.');
          const error = clearCaughtError();
          captureCommitPhaseError(nextEffect, error);
          nextEffect = nextEffect.nextEffect;
        }
      } else {
        try {
          commitLayoutEffects(root, expirationTime);
        } catch (error) {
          invariant(nextEffect !== null, 'Should be working on an effect.');
          captureCommitPhaseError(nextEffect, error);
          nextEffect = nextEffect.nextEffect;
        }
      }
    } while (nextEffect !== null);
    stopCommitLifeCyclesTimer();

    nextEffect = null;

    // Tell Scheduler to yield at the end of the frame, so the browser has an
    // opportunity to paint.
    requestPaint();

    executionContext = prevExecutionContext;
  } else {
    // No effects.
    root.current = finishedWork;
  }

  // If layout work was scheduled, flush it now.
  flushSyncCallbackQueue();
  return null;
}

root.finishedWork = (root.current.alternate: any);

function completeUnitOfWork(unitOfWork: Fiber): Fiber | null {
  // Attempt to complete the current unit of work, then move to the next
  // sibling. If there are no more siblings, return to the parent fiber.
  workInProgress = unitOfWork;
  do {
    // 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 returnFiber = workInProgress.return;

    // Check if the work completed or if something threw.
    if ((workInProgress.effectTag & Incomplete) === NoEffect) {
    // ... 
  
      if (
        returnFiber !== null &&
        // Do not append effects to parents if a sibling failed to complete
        (returnFiber.effectTag & Incomplete) === NoEffect
      ) {
        // 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.
        if (returnFiber.firstEffect === null) {
          returnFiber.firstEffect = workInProgress.firstEffect;
        }
        if (workInProgress.lastEffect !== null) {
          if (returnFiber.lastEffect !== null) {
            returnFiber.lastEffect.nextEffect = workInProgress.firstEffect;
          }
          returnFiber.lastEffect = workInProgress.lastEffect;
        }

        // If this fiber had side-effects, we append it AFTER the children's
        // side-effects. We can perform certain side-effects earlier if needed,
        // by doing multiple passes over the effect list. We don't want to
        // schedule our own side-effect on our own list because if end up
        // reusing children we'll schedule this effect onto itself since we're
        // at the end.
        const effectTag = workInProgress.effectTag;

        // Skip both NoWork and PerformedWork tags when creating the effect
        // list. PerformedWork effect is read by React DevTools but shouldn't be
        // committed.
        if (effectTag > PerformedWork) {
          if (returnFiber.lastEffect !== null) {
            returnFiber.lastEffect.nextEffect = workInProgress;
          } else {
            returnFiber.firstEffect = workInProgress;
          }
          returnFiber.lastEffect = workInProgress;
        }
      }
    }
    // ... 
}

  function reconcileChildFibers(
    returnFiber: Fiber,
    currentFirstChild: Fiber | null,
    newChild: any,
    expirationTime: ExpirationTime,
  ): Fiber | null {
    // This function is not recursive.
    // If the top level item is an array, we treat it as a set of children,
    // not as a fragment. Nested arrays on the other hand will be treated as
    // fragment nodes. Recursion happens at the normal flow.

    // Handle top level unkeyed fragments as if they were arrays.
    // This leads to an ambiguity between <>{[...]}</> and <>...</>.
    // We treat the ambiguous cases above the same.
    const isUnkeyedTopLevelFragment =
      typeof newChild === 'object' &&
      newChild !== null &&
      newChild.type === REACT_FRAGMENT_TYPE &&
      newChild.key === null;
    if (isUnkeyedTopLevelFragment) {
      newChild = newChild.props.children;
    }

    // Handle object types
    const isObject = typeof newChild === 'object' && newChild !== null;

    if (isObject) {
      switch (newChild.$$typeof) {
        case REACT_ELEMENT_TYPE:
          return placeSingleChild(
            reconcileSingleElement(
              returnFiber,
              currentFirstChild,
              newChild,
              expirationTime,
            ),
          );
        case REACT_PORTAL_TYPE:
          return placeSingleChild(
            reconcileSinglePortal(
              returnFiber,
              currentFirstChild,
              newChild,
              expirationTime,
            ),
          );
      }
    }
      
    // ...
}

  function placeSingleChild(newFiber: Fiber): Fiber {
    // This is simpler for the single child case. We only need to do a
    // placement for inserting new children.
    if (shouldTrackSideEffects && newFiber.alternate === null) {
      newFiber.effectTag = Placement;
    }
    return newFiber;
  }

export const reconcileChildFibers = ChildReconciler(true);
export const mountChildFibers = ChildReconciler(false);

export function reconcileChildren(
  current: Fiber | null,
  workInProgress: Fiber,
  nextChildren: any,
  renderExpirationTime: ExpirationTime,
) {
  if (current === null) {
    // If this is a fresh new component that hasn't been rendered yet, we
    // won't update its child set by applying minimal side-effects. Instead,
    // we will add them all to the child before it gets rendered. That means
    // we can optimize this reconciliation pass by not tracking side-effects.
    workInProgress.child = mountChildFibers(
      workInProgress,
      null,
      nextChildren,
      renderExpirationTime,
    );
  } else {
    // If the current child is the same as the work in progress, it means that
    // we haven't yet started any work on these children. Therefore, we use
    // the clone algorithm to create a copy of all the current children.

    // If we had any progressed work already, that is invalid at this point so
    // let's throw it out.
    workInProgress.child = reconcileChildFibers(
      workInProgress,
      current.child,
      nextChildren,
      renderExpirationTime,
    );
  }
}

function commitMutationEffects(root: FiberRoot, renderPriorityLevel) {
  // TODO: Should probably move the bulk of this function to commitWork.
  while (nextEffect !== null) {
    setCurrentDebugFiberInDEV(nextEffect);

    const effectTag = nextEffect.effectTag;

    if (effectTag & ContentReset) {
      commitResetTextContent(nextEffect);
    }

    if (effectTag & Ref) {
      const current = nextEffect.alternate;
      if (current !== null) {
        commitDetachRef(current);
      }
    }

    // The following switch statement is only concerned about placement,
    // updates, and deletions. To avoid needing to add a case for every possible
    // bitmap value, we remove the secondary effects from the effect tag and
    // switch on that value.
    let primaryEffectTag =
      effectTag & (Placement | Update | Deletion | Hydrating);
    switch (primaryEffectTag) {
      case Placement: {
        commitPlacement(nextEffect);
        // Clear the "placement" from effect tag so that we know that this is
        // inserted, before any life-cycles like componentDidMount gets called.
        // TODO: findDOMNode doesn't rely on this any more but isMounted does
        // and isMounted is deprecated anyway so we should be able to kill this.
        nextEffect.effectTag &= ~Placement;
        break;
      }
      case PlacementAndUpdate: {
        // Placement
        commitPlacement(nextEffect);
        // Clear the "placement" from effect tag so that we know that this is
        // inserted, before any life-cycles like componentDidMount gets called.
        nextEffect.effectTag &= ~Placement;

        // Update
        const current = nextEffect.alternate;
        commitWork(current, nextEffect);
        break;
      }
      case Hydrating: {
        nextEffect.effectTag &= ~Hydrating;
        break;
      }
      case HydratingAndUpdate: {
        nextEffect.effectTag &= ~Hydrating;

        // Update
        const current = nextEffect.alternate;
        commitWork(current, nextEffect);
        break;
      }
      case Update: {
        const current = nextEffect.alternate;
        commitWork(current, nextEffect);
        break;
      }
      case Deletion: {
        commitDeletion(root, nextEffect, renderPriorityLevel);
        break;
      }
    }

    // TODO: Only record a mutation effect if primaryEffectTag is non-zero.
    recordEffect();

    resetCurrentDebugFiberInDEV();
    nextEffect = nextEffect.nextEffect;
  }
}

function commitPlacement(finishedWork: Fiber): void {
  if (!supportsMutation) {
    return;
  }

  // Recursively insert all host nodes into the parent.
  const parentFiber = getHostParentFiber(finishedWork);

  // Note: these two variables *must* always be updated together.
  let parent;
  let isContainer;
  const parentStateNode = parentFiber.stateNode;
  switch (parentFiber.tag) {
    case HostComponent:
      parent = parentStateNode;
      isContainer = false;
      break;
    case HostRoot:
      parent = parentStateNode.containerInfo;
      isContainer = true;
      break;
    case HostPortal:
      parent = parentStateNode.containerInfo;
      isContainer = true;
      break;
    case FundamentalComponent:
      if (enableFundamentalAPI) {
        parent = parentStateNode.instance;
        isContainer = false;
      }
    // eslint-disable-next-line-no-fallthrough
    default:
      invariant(
        false,
        'Invalid host parent fiber. This error is likely caused by a bug ' +
          'in React. Please file an issue.',
      );
  }
  if (parentFiber.effectTag & ContentReset) {
    // Reset the text content of the parent before doing any insertions
    resetTextContent(parent);
    // Clear ContentReset from the effect tag
    parentFiber.effectTag &= ~ContentReset;
  }

  const before = getHostSibling(finishedWork);
  // We only have the top Fiber that was inserted but we need to recurse down its
  // children to find all the terminal nodes.
  if (isContainer) {
    insertOrAppendPlacementNodeIntoContainer(finishedWork, before, parent);
  } else {
    insertOrAppendPlacementNode(finishedWork, before, parent);
  }
}

function insertOrAppendPlacementNodeIntoContainer(
  node: Fiber,
  before: ?Instance,
  parent: Container,
): void {
  const {tag} = node;
  const isHost = tag === HostComponent || tag === HostText;
  if (isHost || (enableFundamentalAPI && tag === FundamentalComponent)) {
    const stateNode = isHost ? node.stateNode : node.stateNode.instance;
    if (before) {
      insertInContainerBefore(parent, stateNode, before);
    } else {
      appendChildToContainer(parent, stateNode);
    }
  } else if (tag === HostPortal) {
    // If the insertion itself is a portal, then we don't want to traverse
    // down its children. Instead, we'll get insertions from each child in
    // the portal directly.
  } else {
    const child = node.child;
    if (child !== null) {
      insertOrAppendPlacementNodeIntoContainer(child, before, parent);
      let sibling = child.sibling;
      while (sibling !== null) {
        insertOrAppendPlacementNodeIntoContainer(sibling, before, parent);
        sibling = sibling.sibling;
      }
    }
  }
}

export function appendChildToContainer(
  container: Container,
  child: Instance | TextInstance,
): void {
  let parentNode;
  if (container.nodeType === COMMENT_NODE) {
    parentNode = (container.parentNode: any);
    parentNode.insertBefore(child, container);
  } else {
    parentNode = container;
    parentNode.appendChild(child);
  }
  // This container might be used for a portal.
  // If something inside a portal is clicked, that click should bubble
  // through the React tree. However, on Mobile Safari the click would
  // never bubble through the *DOM* tree unless an ancestor with onclick
  // event exists. So we wouldn't see it and dispatch it.
  // This is why we ensure that non React root containers have inline onclick
  // defined.
  // https://github.com/facebook/react/issues/11918
  const reactRootContainer = container._reactRootContainer;
  if (
    (reactRootContainer === null || reactRootContainer === undefined) &&
    parentNode.onclick === null
  ) {
    // TODO: This cast may not be sound for SVG, MathML or custom elements.
    trapClickOnNonInteractiveElement(((parentNode: any): HTMLElement));
  }
}