in packages/react-reconciler/src/ReactFiberBeginWork.new.js [3774:4047]
function beginWork(
current: Fiber | null,
workInProgress: Fiber,
renderLanes: Lanes,
): Fiber | null {
if (__DEV__) {
if (workInProgress._debugNeedsRemount && current !== null) {
// This will restart the begin phase with a new fiber.
return remountFiber(
current,
workInProgress,
createFiberFromTypeAndProps(
workInProgress.type,
workInProgress.key,
workInProgress.pendingProps,
workInProgress._debugOwner || null,
workInProgress.mode,
workInProgress.lanes,
),
);
}
}
if (current !== null) {
const oldProps = current.memoizedProps;
const newProps = workInProgress.pendingProps;
if (
oldProps !== newProps ||
hasLegacyContextChanged() ||
// Force a re-render if the implementation changed due to hot reload:
(__DEV__ ? workInProgress.type !== current.type : false)
) {
// If props or context changed, mark the fiber as having performed work.
// This may be unset if the props are determined to be equal later (memo).
didReceiveUpdate = true;
} else {
// Neither props nor legacy context changes. Check if there's a pending
// update or context change.
const hasScheduledUpdateOrContext = checkScheduledUpdateOrContext(
current,
renderLanes,
);
if (
!hasScheduledUpdateOrContext &&
// If this is the second pass of an error or suspense boundary, there
// may not be work scheduled on `current`, so we check for this flag.
(workInProgress.flags & DidCapture) === NoFlags
) {
// No pending updates or context. Bail out now.
didReceiveUpdate = false;
return attemptEarlyBailoutIfNoScheduledUpdate(
current,
workInProgress,
renderLanes,
);
}
if ((current.flags & ForceUpdateForLegacySuspense) !== NoFlags) {
// This is a special case that only exists for legacy mode.
// See https://github.com/facebook/react/pull/19216.
didReceiveUpdate = true;
} else {
// An update was scheduled on this fiber, but there are no new props
// nor legacy context. Set this to false. If an update queue or context
// consumer produces a changed value, it will set this to true. Otherwise,
// the component will assume the children have not changed and bail out.
didReceiveUpdate = false;
}
}
} else {
didReceiveUpdate = false;
if (getIsHydrating() && isForkedChild(workInProgress)) {
// Check if this child belongs to a list of muliple children in
// its parent.
//
// In a true multi-threaded implementation, we would render children on
// parallel threads. This would represent the beginning of a new render
// thread for this subtree.
//
// We only use this for id generation during hydration, which is why the
// logic is located in this special branch.
const slotIndex = workInProgress.index;
const numberOfForks = getForksAtLevel(workInProgress);
pushTreeId(workInProgress, numberOfForks, slotIndex);
}
}
// Before entering the begin phase, clear pending update priority.
// TODO: This assumes that we're about to evaluate the component and process
// the update queue. However, there's an exception: SimpleMemoComponent
// sometimes bails out later in the begin phase. This indicates that we should
// move this assignment out of the common path and into each branch.
workInProgress.lanes = NoLanes;
switch (workInProgress.tag) {
case IndeterminateComponent: {
return mountIndeterminateComponent(
current,
workInProgress,
workInProgress.type,
renderLanes,
);
}
case LazyComponent: {
const elementType = workInProgress.elementType;
return mountLazyComponent(
current,
workInProgress,
elementType,
renderLanes,
);
}
case FunctionComponent: {
const Component = workInProgress.type;
const unresolvedProps = workInProgress.pendingProps;
const resolvedProps =
workInProgress.elementType === Component
? unresolvedProps
: resolveDefaultProps(Component, unresolvedProps);
return updateFunctionComponent(
current,
workInProgress,
Component,
resolvedProps,
renderLanes,
);
}
case ClassComponent: {
const Component = workInProgress.type;
const unresolvedProps = workInProgress.pendingProps;
const resolvedProps =
workInProgress.elementType === Component
? unresolvedProps
: resolveDefaultProps(Component, unresolvedProps);
return updateClassComponent(
current,
workInProgress,
Component,
resolvedProps,
renderLanes,
);
}
case HostRoot:
return updateHostRoot(current, workInProgress, renderLanes);
case HostComponent:
return updateHostComponent(current, workInProgress, renderLanes);
case HostText:
return updateHostText(current, workInProgress);
case SuspenseComponent:
return updateSuspenseComponent(current, workInProgress, renderLanes);
case HostPortal:
return updatePortalComponent(current, workInProgress, renderLanes);
case ForwardRef: {
const type = workInProgress.type;
const unresolvedProps = workInProgress.pendingProps;
const resolvedProps =
workInProgress.elementType === type
? unresolvedProps
: resolveDefaultProps(type, unresolvedProps);
return updateForwardRef(
current,
workInProgress,
type,
resolvedProps,
renderLanes,
);
}
case Fragment:
return updateFragment(current, workInProgress, renderLanes);
case Mode:
return updateMode(current, workInProgress, renderLanes);
case Profiler:
return updateProfiler(current, workInProgress, renderLanes);
case ContextProvider:
return updateContextProvider(current, workInProgress, renderLanes);
case ContextConsumer:
return updateContextConsumer(current, workInProgress, renderLanes);
case MemoComponent: {
const type = workInProgress.type;
const unresolvedProps = workInProgress.pendingProps;
// Resolve outer props first, then resolve inner props.
let resolvedProps = resolveDefaultProps(type, unresolvedProps);
if (__DEV__) {
if (workInProgress.type !== workInProgress.elementType) {
const outerPropTypes = type.propTypes;
if (outerPropTypes) {
checkPropTypes(
outerPropTypes,
resolvedProps, // Resolved for outer only
'prop',
getComponentNameFromType(type),
);
}
}
}
resolvedProps = resolveDefaultProps(type.type, resolvedProps);
return updateMemoComponent(
current,
workInProgress,
type,
resolvedProps,
renderLanes,
);
}
case SimpleMemoComponent: {
return updateSimpleMemoComponent(
current,
workInProgress,
workInProgress.type,
workInProgress.pendingProps,
renderLanes,
);
}
case IncompleteClassComponent: {
const Component = workInProgress.type;
const unresolvedProps = workInProgress.pendingProps;
const resolvedProps =
workInProgress.elementType === Component
? unresolvedProps
: resolveDefaultProps(Component, unresolvedProps);
return mountIncompleteClassComponent(
current,
workInProgress,
Component,
resolvedProps,
renderLanes,
);
}
case SuspenseListComponent: {
return updateSuspenseListComponent(current, workInProgress, renderLanes);
}
case ScopeComponent: {
if (enableScopeAPI) {
return updateScopeComponent(current, workInProgress, renderLanes);
}
break;
}
case OffscreenComponent: {
return updateOffscreenComponent(current, workInProgress, renderLanes);
}
case LegacyHiddenComponent: {
if (enableLegacyHidden) {
return updateLegacyHiddenComponent(
current,
workInProgress,
renderLanes,
);
}
break;
}
case CacheComponent: {
if (enableCache) {
return updateCacheComponent(current, workInProgress, renderLanes);
}
break;
}
case TracingMarkerComponent: {
if (enableTransitionTracing) {
return updateTracingMarkerComponent(
current,
workInProgress,
renderLanes,
);
}
break;
}
}
throw new Error(
`Unknown unit of work tag (${workInProgress.tag}). This error is likely caused by a bug in ` +
'React. Please file an issue.',
);
}