From c0d7023a88d33aad7f01125645cf8322a5e808b8 Mon Sep 17 00:00:00 2001
From: Dan Abramov <dan.abramov@gmail.com>
Date: Sat, 20 Apr 2019 21:42:30 +0100
Subject: [PATCH 1/2] Replace WeakSet with return pointer check

---
 src/backend/renderer.js | 14 ++------------
 1 file changed, 2 insertions(+), 12 deletions(-)

diff --git a/src/backend/renderer.js b/src/backend/renderer.js
index 728f1c0e59..a4626740b3 100644
--- a/src/backend/renderer.js
+++ b/src/backend/renderer.js
@@ -589,11 +589,6 @@ export function attach(
   let pendingSimulatedUnmountedIDs: Array<number> = [];
   let pendingOperationsQueue: Array<Uint32Array> | null = [];
 
-  // We keep track of which Fibers have been reported as unmounted by React
-  // during this commit phase so that we don't try to "hide" them or their
-  // children when Suspense flips to fallback. These Fibers won't have IDs.
-  let fibersUnmountedInThisCommitPhase: WeakSet<Fiber> = new WeakSet();
-
   // TODO: we could make this layer DEV-only and write directly to pendingOperations.
   let nextOperation: Array<number> = [];
   function beginNextOperation(size: number): void {
@@ -683,7 +678,6 @@ export function attach(
     pendingOperations.length = 0;
     pendingRealUnmountedIDs.length = 0;
     pendingSimulatedUnmountedIDs.length = 0;
-    fibersUnmountedInThisCommitPhase = new WeakSet();
   }
 
   function recordMount(fiber: Fiber, parentFiber: Fiber | null) {
@@ -890,9 +884,8 @@ export function attach(
 
     while (child !== null) {
       // Record simulated unmounts children-first.
-      // We might find real committed unmounts along the way--skip them.
-      // Otherwise we would send duplicated messages for the same IDs.
-      if (!fibersUnmountedInThisCommitPhase.has(child)) {
+      // We skip nodes without return because those are real unmounts.
+      if (child.return !== null) {
         unmountFiberChildrenRecursively(child);
         recordUnmount(child, true);
       }
@@ -1167,9 +1160,6 @@ export function attach(
   }
 
   function handleCommitFiberUnmount(fiber) {
-    // Remeber this is a real deletion so we don't
-    // go down this tree when hiding Suspense nodes.
-    fibersUnmountedInThisCommitPhase.add(fiber);
     // This is not recursive.
     // We can't traverse fibers after unmounting so instead
     // we rely on React telling us about each unmount.

From 006e03c38e191303b797cb69c35cec1f1069c7cd Mon Sep 17 00:00:00 2001
From: Dan Abramov <dan.abramov@gmail.com>
Date: Sat, 20 Apr 2019 22:17:12 +0100
Subject: [PATCH 2/2] Ignore leading edge of find-by-DOM throttle

---
 src/backend/agent.js | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/backend/agent.js b/src/backend/agent.js
index 74676d44b9..378a70f271 100644
--- a/src/backend/agent.js
+++ b/src/backend/agent.js
@@ -525,6 +525,9 @@ export default class Agent extends EventEmitter {
         this._bridge.send('selectFiber', id);
       }
     }),
-    200
+    200,
+    // Don't change the selection in the very first 200ms
+    // because those are usually unintentional as you lift the cursor.
+    { leading: false }
   );
 }