Flush legacy passive effects at beginning of event

Fixes test added in previous commit.
facebook · Jul 10, 2021 · 838aa8b · 838aa8b
1 parent 1a63add
commit 838aa8b
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diff --git a/packages/react-reconciler/src/ReactFiberWorkLoop.new.js b/packages/react-reconciler/src/ReactFiberWorkLoop.new.js
@@ -1082,6 +1082,15 @@ export function flushSyncWithoutWarningIfAlreadyRendering<A, R>(
   fn: A => R,
   a: A,
 ): R {
+  // In legacy mode, we flush pending passive effects at the beginning of the
+  // next event, not at the end of the previous one.
+  if (
+    rootWithPendingPassiveEffects !== null &&
+    rootWithPendingPassiveEffects.tag === LegacyRoot
+  ) {
+    flushPassiveEffects();
+  }
+
   const prevExecutionContext = executionContext;
   executionContext |= BatchedContext;
 

diff --git a/packages/react-reconciler/src/ReactFiberWorkLoop.old.js b/packages/react-reconciler/src/ReactFiberWorkLoop.old.js
@@ -1082,6 +1082,15 @@ export function flushSyncWithoutWarningIfAlreadyRendering<A, R>(
   fn: A => R,
   a: A,
 ): R {
+  // In legacy mode, we flush pending passive effects at the beginning of the
+  // next event, not at the end of the previous one.
+  if (
+    rootWithPendingPassiveEffects !== null &&
+    rootWithPendingPassiveEffects.tag === LegacyRoot
+  ) {
+    flushPassiveEffects();
+  }
+
   const prevExecutionContext = executionContext;
   executionContext |= BatchedContext;