Resume immediately pinged fiber without unwinding

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

@@ -357,7 +357,7 @@ function throwException(
   sourceFiber: Fiber,
   value: mixed,
   rootRenderLanes: Lanes,
-) {
+): Wakeable | null {
   // The source fiber did not complete.
   sourceFiber.flags |= Incomplete;
 
@@ -459,7 +459,7 @@ function throwException(
       if (suspenseBoundary.mode & ConcurrentMode) {
         attachPingListener(root, wakeable, rootRenderLanes);
       }
-      return;
+      return wakeable;
     } else {
       // No boundary was found. Unless this is a sync update, this is OK.
       // We can suspend and wait for more data to arrive.
@@ -474,7 +474,7 @@ function throwException(
         // This case also applies to initial hydration.
         attachPingListener(root, wakeable, rootRenderLanes);
         renderDidSuspendDelayIfPossible();
-        return;
+        return wakeable;
       }
 
       // This is a sync/discrete update. We treat this case like an error
@@ -517,7 +517,7 @@ function throwException(
         // Even though the user may not be affected by this error, we should
         // still log it so it can be fixed.
         queueHydrationError(createCapturedValueAtFiber(value, sourceFiber));
-        return;
+        return null;
       }
     } else {
       // Otherwise, fall through to the error path.
@@ -540,7 +540,7 @@ function throwException(
         workInProgress.lanes = mergeLanes(workInProgress.lanes, lane);
         const update = createRootErrorUpdate(workInProgress, errorInfo, lane);
         enqueueCapturedUpdate(workInProgress, update);
-        return;
+        return null;
       }
       case ClassComponent:
         // Capture and retry
@@ -564,14 +564,15 @@ function throwException(
             lane,
           );
           enqueueCapturedUpdate(workInProgress, update);
-          return;
+          return null;
         }
         break;
       default:
         break;
     }
     workInProgress = workInProgress.return;
   } while (workInProgress !== null);
+  return null;
 }
 
 export {throwException, createRootErrorUpdate, createClassErrorUpdate};

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

@@ -357,7 +357,7 @@ function throwException(
   sourceFiber: Fiber,
   value: mixed,
   rootRenderLanes: Lanes,
-) {
+): Wakeable | null {
   // The source fiber did not complete.
   sourceFiber.flags |= Incomplete;
 
@@ -459,7 +459,7 @@ function throwException(
       if (suspenseBoundary.mode & ConcurrentMode) {
         attachPingListener(root, wakeable, rootRenderLanes);
       }
-      return;
+      return wakeable;
     } else {
       // No boundary was found. Unless this is a sync update, this is OK.
       // We can suspend and wait for more data to arrive.
@@ -474,7 +474,7 @@ function throwException(
         // This case also applies to initial hydration.
         attachPingListener(root, wakeable, rootRenderLanes);
         renderDidSuspendDelayIfPossible();
-        return;
+        return wakeable;
       }
 
       // This is a sync/discrete update. We treat this case like an error
@@ -517,7 +517,7 @@ function throwException(
         // Even though the user may not be affected by this error, we should
         // still log it so it can be fixed.
         queueHydrationError(createCapturedValueAtFiber(value, sourceFiber));
-        return;
+        return null;
       }
     } else {
       // Otherwise, fall through to the error path.
@@ -540,7 +540,7 @@ function throwException(
         workInProgress.lanes = mergeLanes(workInProgress.lanes, lane);
         const update = createRootErrorUpdate(workInProgress, errorInfo, lane);
         enqueueCapturedUpdate(workInProgress, update);
-        return;
+        return null;
       }
       case ClassComponent:
         // Capture and retry
@@ -564,14 +564,15 @@ function throwException(
             lane,
           );
           enqueueCapturedUpdate(workInProgress, update);
-          return;
+          return null;
         }
         break;
       default:
         break;
     }
     workInProgress = workInProgress.return;
   } while (workInProgress !== null);
+  return null;
 }
 
 export {throwException, createRootErrorUpdate, createClassErrorUpdate};

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

@@ -0,0 +1,50 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ */
+
+import type {Wakeable} from 'shared/ReactTypes';
+
+let suspendedWakeable: Wakeable | null = null;
+let wasPinged = false;
+let adHocSuspendCount: number = 0;
+
+const MAX_AD_HOC_SUSPEND_COUNT = 50;
+
+export function suspendedWakeableWasPinged() {
+  return wasPinged;
+}
+
+export function trackSuspendedWakeable(wakeable: Wakeable) {
+  adHocSuspendCount++;
+  suspendedWakeable = wakeable;
+}
+
+export function attemptToPingSuspendedWakeable(wakeable: Wakeable) {
+  if (wakeable === suspendedWakeable) {
+    // This ping is from the wakeable that just suspended. Mark it as pinged.
+    // When the work loop resumes, we'll immediately try rendering the fiber
+    // again instead of unwinding the stack.
+    wasPinged = true;
+    return true;
+  }
+  return false;
+}
+
+export function resetWakeableState() {
+  suspendedWakeable = null;
+  wasPinged = false;
+  adHocSuspendCount = 0;
+}
+
+export function throwIfInfinitePingLoopDetected() {
+  if (adHocSuspendCount > MAX_AD_HOC_SUSPEND_COUNT) {
+    // TODO: Guard against an infinite loop by throwing an error if the same
+    // component suspends too many times in a row. This should be thrown from
+    // the render phase so that it gets the component stack.
+  }
+}

packages/react-reconciler/src/ReactFiberWakeable.old.js

@@ -0,0 +1,50 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ */
+
+import type {Wakeable} from 'shared/ReactTypes';
+
+let suspendedWakeable: Wakeable | null = null;
+let wasPinged = false;
+let adHocSuspendCount: number = 0;
+
+const MAX_AD_HOC_SUSPEND_COUNT = 50;
+
+export function suspendedWakeableWasPinged() {
+  return wasPinged;
+}
+
+export function trackSuspendedWakeable(wakeable: Wakeable) {
+  adHocSuspendCount++;
+  suspendedWakeable = wakeable;
+}
+
+export function attemptToPingSuspendedWakeable(wakeable: Wakeable) {
+  if (wakeable === suspendedWakeable) {
+    // This ping is from the wakeable that just suspended. Mark it as pinged.
+    // When the work loop resumes, we'll immediately try rendering the fiber
+    // again instead of unwinding the stack.
+    wasPinged = true;
+    return true;
+  }
+  return false;
+}
+
+export function resetWakeableState() {
+  suspendedWakeable = null;
+  wasPinged = false;
+  adHocSuspendCount = 0;
+}
+
+export function throwIfInfinitePingLoopDetected() {
+  if (adHocSuspendCount > MAX_AD_HOC_SUSPEND_COUNT) {
+    // TODO: Guard against an infinite loop by throwing an error if the same
+    // component suspends too many times in a row. This should be thrown from
+    // the render phase so that it gets the component stack.
+  }
+}