Remove remaining references to effect list (#19673)

* Remove `firstEffect` null check

This is the last remaining place where the effect list has semantic
implications.

I've replaced it with a check of `effectTag` and `subtreeTag`, to see
if there are any effects in the whole tree. This matches the semantics
of the old check. However, I think only reason this optimization exists
is because it affects profiling. We should reconsider whether this
is necessary.

* Remove remaining references to effect list

We no longer use the effect list anywhere in our implementation. It's
been replaced by a recursive traversal in the commit phase.

This removes all references to the effect list in the new fork.

packages/react-reconciler/src/ReactChildFiber.new.js

@@ -277,28 +277,13 @@ function ChildReconciler(shouldTrackSideEffects) {
       // Noop.
       return;
     }
-    // Deletions are added in reversed order so we add it to the front.
-    // At this point, the return fiber's effect list is empty except for
-    // deletions, so we can just append the deletion to the list. The remaining
-    // effects aren't added until the complete phase. Once we implement
-    // resuming, this may not be true.
-    // TODO (effects) Get rid of effects list update here.
-    const last = returnFiber.lastEffect;
-    if (last !== null) {
-      last.nextEffect = childToDelete;
-      returnFiber.lastEffect = childToDelete;
-    } else {
-      returnFiber.firstEffect = returnFiber.lastEffect = childToDelete;
-    }
     const deletions = returnFiber.deletions;
     if (deletions === null) {
       returnFiber.deletions = [childToDelete];
-      // TODO (effects) Rename this to better reflect its new usage (e.g. ChildDeletions)
       returnFiber.effectTag |= Deletion;
     } else {
       deletions.push(childToDelete);
     }
-    childToDelete.nextEffect = null;
   }
 
   function deleteRemainingChildren(

packages/react-reconciler/src/ReactFiber.new.js

@@ -147,10 +147,6 @@ function FiberNode(
   this.effectTag = NoEffect;
   this.subtreeTag = NoSubtreeEffect;
   this.deletions = null;
-  this.nextEffect = null;
-
-  this.firstEffect = null;
-  this.lastEffect = null;
 
   this.lanes = NoLanes;
   this.childLanes = NoLanes;
@@ -291,11 +287,6 @@ export function createWorkInProgress(current: Fiber, pendingProps: any): Fiber {
     workInProgress.subtreeTag = NoSubtreeEffect;
     workInProgress.deletions = null;
 
-    // The effect list is no longer valid.
-    workInProgress.nextEffect = null;
-    workInProgress.firstEffect = null;
-    workInProgress.lastEffect = null;
-
     if (enableProfilerTimer) {
       // We intentionally reset, rather than copy, actualDuration & actualStartTime.
       // This prevents time from endlessly accumulating in new commits.
@@ -374,18 +365,14 @@ export function resetWorkInProgress(workInProgress: Fiber, renderLanes: Lanes) {
   // that child fiber is setting, not the reconciliation.
   workInProgress.effectTag &= Placement;
 
-  // The effect list is no longer valid.
-  workInProgress.nextEffect = null;
-  workInProgress.firstEffect = null;
-  workInProgress.lastEffect = null;
-
   const current = workInProgress.alternate;
   if (current === null) {
     // Reset to createFiber's initial values.
     workInProgress.childLanes = NoLanes;
     workInProgress.lanes = renderLanes;
 
     workInProgress.child = null;
+    workInProgress.subtreeTag = NoSubtreeEffect;
     workInProgress.memoizedProps = null;
     workInProgress.memoizedState = null;
     workInProgress.updateQueue = null;
@@ -406,6 +393,8 @@ export function resetWorkInProgress(workInProgress: Fiber, renderLanes: Lanes) {
     workInProgress.lanes = current.lanes;
 
     workInProgress.child = current.child;
+    workInProgress.subtreeTag = current.subtreeTag;
+    workInProgress.deletions = null;
     workInProgress.memoizedProps = current.memoizedProps;
     workInProgress.memoizedState = current.memoizedState;
     workInProgress.updateQueue = current.updateQueue;
@@ -830,9 +819,6 @@ export function assignFiberPropertiesInDEV(
   target.effectTag = source.effectTag;
   target.subtreeTag = source.subtreeTag;
   target.deletions = source.deletions;
-  target.nextEffect = source.nextEffect;
-  target.firstEffect = source.firstEffect;
-  target.lastEffect = source.lastEffect;
   target.lanes = source.lanes;
   target.childLanes = source.childLanes;
   target.alternate = source.alternate;

packages/react-reconciler/src/ReactFiberBeginWork.new.js

@@ -2063,8 +2063,6 @@ function updateSuspensePrimaryChildren(
   primaryChildFragment.sibling = null;
   if (currentFallbackChildFragment !== null) {
     // Delete the fallback child fragment
-    currentFallbackChildFragment.nextEffect = null;
-    workInProgress.firstEffect = workInProgress.lastEffect = currentFallbackChildFragment;
     const deletions = workInProgress.deletions;
     if (deletions === null) {
       workInProgress.deletions = [currentFallbackChildFragment];
@@ -2129,21 +2127,8 @@ function updateSuspenseFallbackChildren(
 
     // The fallback fiber was added as a deletion effect during the first pass.
     // However, since we're going to remain on the fallback, we no longer want
-    // to delete it. So we need to remove it from the list. Deletions are stored
-    // on the same list as effects. We want to keep the effects from the primary
-    // tree. So we copy the primary child fragment's effect list, which does not
-    // include the fallback deletion effect.
-    const progressedLastEffect = primaryChildFragment.lastEffect;
-    if (progressedLastEffect !== null) {
-      workInProgress.firstEffect = primaryChildFragment.firstEffect;
-      workInProgress.lastEffect = progressedLastEffect;
-      progressedLastEffect.nextEffect = null;
-      workInProgress.deletions = null;
-    } else {
-      // TODO: Reset this somewhere else? Lol legacy mode is so weird.
-      workInProgress.firstEffect = workInProgress.lastEffect = null;
-      workInProgress.deletions = null;
-    }
+    // to delete it.
+    workInProgress.deletions = null;
   } else {
     primaryChildFragment = createWorkInProgressOffscreenFiber(
       currentPrimaryChildFragment,
@@ -2633,7 +2618,6 @@ function initSuspenseListRenderState(
   tail: null | Fiber,
   lastContentRow: null | Fiber,
   tailMode: SuspenseListTailMode,
-  lastEffectBeforeRendering: null | Fiber,
 ): void {
   const renderState: null | SuspenseListRenderState =
     workInProgress.memoizedState;
@@ -2645,7 +2629,6 @@ function initSuspenseListRenderState(
       last: lastContentRow,
       tail: tail,
       tailMode: tailMode,
-      lastEffect: lastEffectBeforeRendering,
     }: SuspenseListRenderState);
   } else {
     // We can reuse the existing object from previous renders.
@@ -2655,7 +2638,6 @@ function initSuspenseListRenderState(
     renderState.last = lastContentRow;
     renderState.tail = tail;
     renderState.tailMode = tailMode;
-    renderState.lastEffect = lastEffectBeforeRendering;
   }
 }
 
@@ -2737,7 +2719,6 @@ function updateSuspenseListComponent(
           tail,
           lastContentRow,
           tailMode,
-          workInProgress.lastEffect,
         );
         break;
       }
@@ -2769,7 +2750,6 @@ function updateSuspenseListComponent(
           tail,
           null, // last
           tailMode,
-          workInProgress.lastEffect,
         );
         break;
       }
@@ -2780,7 +2760,6 @@ function updateSuspenseListComponent(
           null, // tail
           null, // last
           undefined,
-          workInProgress.lastEffect,
         );
         break;
       }
@@ -3040,13 +3019,6 @@ function remountFiber(
 
     // Delete the old fiber and place the new one.
     // Since the old fiber is disconnected, we have to schedule it manually.
-    const last = returnFiber.lastEffect;
-    if (last !== null) {
-      last.nextEffect = current;
-      returnFiber.lastEffect = current;
-    } else {
-      returnFiber.firstEffect = returnFiber.lastEffect = current;
-    }
     const deletions = returnFiber.deletions;
     if (deletions === null) {
       returnFiber.deletions = [current];
@@ -3055,7 +3027,6 @@ function remountFiber(
     } else {
       deletions.push(current);
     }
-    current.nextEffect = null;
 
     newWorkInProgress.effectTag |= Placement;
 
@@ -3256,7 +3227,6 @@ function beginWork(
             // update in the past but didn't complete it.
             renderState.rendering = null;
             renderState.tail = null;
-            renderState.lastEffect = null;
           }
           pushSuspenseContext(workInProgress, suspenseStackCursor.current);
 

packages/react-reconciler/src/ReactFiberCompleteWork.new.js

@@ -1049,18 +1049,8 @@ function completeWork(
 
                 // Rerender the whole list, but this time, we'll force fallbacks
                 // to stay in place.
-                // Reset the effect list before doing the second pass since that's now invalid.
-                if (renderState.lastEffect === null) {
-                  workInProgress.firstEffect = null;
-                  workInProgress.subtreeTag = NoEffect;
-                  let child = workInProgress.child;
-                  while (child !== null) {
-                    child.deletions = null;
-                    child = child.sibling;
-                  }
-                }
-                workInProgress.lastEffect = renderState.lastEffect;
                 // Reset the child fibers to their original state.
+                workInProgress.subtreeTag = NoEffect;
                 resetChildFibers(workInProgress, renderLanes);
 
                 // Set up the Suspense Context to force suspense and immediately
@@ -1128,15 +1118,6 @@ function completeWork(
               !renderedTail.alternate &&
               !getIsHydrating() // We don't cut it if we're hydrating.
             ) {
-              // We need to delete the row we just rendered.
-              // Reset the effect list to what it was before we rendered this
-              // child. The nested children have already appended themselves.
-              const lastEffect = (workInProgress.lastEffect =
-                renderState.lastEffect);
-              // Remove any effects that were appended after this point.
-              if (lastEffect !== null) {
-                lastEffect.nextEffect = null;
-              }
               // We're done.
               return null;
             }
@@ -1192,7 +1173,6 @@ function completeWork(
         const next = renderState.tail;
         renderState.rendering = next;
         renderState.tail = next.sibling;
-        renderState.lastEffect = workInProgress.lastEffect;
         renderState.renderingStartTime = now();
         next.sibling = null;
 

packages/react-reconciler/src/ReactFiberHydrationContext.new.js

@@ -133,18 +133,6 @@ function deleteHydratableInstance(
   } else {
     deletions.push(childToDelete);
   }
-
-  // This might seem like it belongs on progressedFirstDeletion. However,
-  // these children are not part of the reconciliation list of children.
-  // Even if we abort and rereconcile the children, that will try to hydrate
-  // again and the nodes are still in the host tree so these will be
-  // recreated.
-  if (returnFiber.lastEffect !== null) {
-    returnFiber.lastEffect.nextEffect = childToDelete;
-    returnFiber.lastEffect = childToDelete;
-  } else {
-    returnFiber.firstEffect = returnFiber.lastEffect = childToDelete;
-  }
 }
 
 function insertNonHydratedInstance(returnFiber: Fiber, fiber: Fiber) {

packages/react-reconciler/src/ReactFiberSuspenseComponent.new.js

@@ -49,9 +49,6 @@ export type SuspenseListRenderState = {|
   tail: null | Fiber,
   // Tail insertions setting.
   tailMode: SuspenseListTailMode,
-  // Last Effect before we rendered the "rendering" item.
-  // Used to remove new effects added by the rendered item.
-  lastEffect: null | Fiber,
 |};
 
 export function shouldCaptureSuspense(

packages/react-reconciler/src/ReactFiberThrow.new.js

@@ -185,8 +185,6 @@ function throwException(
 ) {
   // The source fiber did not complete.
   sourceFiber.effectTag |= Incomplete;
-  // Its effect list is no longer valid.
-  sourceFiber.firstEffect = sourceFiber.lastEffect = null;
 
   if (
     value !== null &&