From b76372c93dcfb3646e8b231fccce4cb763c54db3 Mon Sep 17 00:00:00 2001
From: Brian Vaughn <bvaughn@fb.com>
Date: Sat, 13 Apr 2019 18:29:39 -0700
Subject: [PATCH] Fixed an edge case profiling bug where the number of commits
 was wrong

---
 src/devtools/store.js | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/src/devtools/store.js b/src/devtools/store.js
index 38d33f2a6a..63d87f2544 100644
--- a/src/devtools/store.js
+++ b/src/devtools/store.js
@@ -410,24 +410,19 @@ export default class Store extends EventEmitter {
   startProfiling(): void {
     this._bridge.send('startProfiling');
 
-    // Invalidate suspense cache if profiling data is being (re-)recorded.
-    // Note that we clear now because any existing data is "stale".
-    this._profilingCache.invalidate();
-
-    this._isProfiling = false;
-    this.emit('isProfiling');
+    // Don't actually update the local profiling boolean yet!
+    // Wait for onProfilingStatus() to confirm the status has changed.
+    // This ensures the frontend and backend are in sync wrt which commits were profiled.
+    // We do this to avoid mismatches on e.g. CommitTreeBuilder that would cause errors.
   }
 
   stopProfiling(): void {
     this._bridge.send('stopProfiling');
 
-    // Invalidate suspense cache if profiling data is being (re-)recorded.
-    // Note that we clear again, in case any views read from the cache while profiling.
-    // (That would have resolved a now-stale value without any profiling data.)
-    this._profilingCache.invalidate();
-
-    this._isProfiling = false;
-    this.emit('isProfiling');
+    // Don't actually update the local profiling boolean yet!
+    // Wait for onProfilingStatus() to confirm the status has changed.
+    // This ensures the frontend and backend are in sync wrt which commits were profiled.
+    // We do this to avoid mismatches on e.g. CommitTreeBuilder that would cause errors.
   }
 
   toggleIsCollapsed(id: number, isCollapsed: boolean): void {
@@ -812,6 +807,12 @@ export default class Store extends EventEmitter {
 
     if (this._isProfiling !== isProfiling) {
       this._isProfiling = isProfiling;
+
+      // Invalidate suspense cache if profiling data is being (re-)recorded.
+      // Note that we clear again, in case any views read from the cache while profiling.
+      // (That would have resolved a now-stale value without any profiling data.)
+      this._profilingCache.invalidate();
+
       this.emit('isProfiling');
     }
   };