[DevTools] Don't keep stale root instances around we never mounted

Author: eps1lon

packages/react-devtools-shared/src/backend/fiber/renderer.js

@@ -1516,7 +1516,7 @@ export function attach(
       currentRoot = rootInstance;
       unmountInstanceRecursively(rootInstance);
       rootToFiberInstanceMap.delete(root);
-      flushPendingEvents(root);
+      flushPendingEvents();
       currentRoot = (null: any);
     });
 
@@ -1541,7 +1541,7 @@ export function attach(
       currentRoot = newRoot;
       setRootPseudoKey(currentRoot.id, root.current);
       mountFiberRecursively(root.current, false);
-      flushPendingEvents(root);
+      flushPendingEvents();
       currentRoot = (null: any);
     });
 
@@ -2099,7 +2099,7 @@ export function attach(
     }
   }
 
-  function flushPendingEvents(root: Object): void {
+  function flushPendingEvents(): void {
     if (shouldBailoutWithPendingOperations()) {
       // If we aren't profiling, we can just bail out here.
       // No use sending an empty update over the bridge.
@@ -5349,7 +5349,7 @@ export function attach(
 
         mountFiberRecursively(root.current, false);
 
-        flushPendingEvents(root);
+        flushPendingEvents();
 
         needsToFlushComponentLogs = false;
         currentRoot = (null: any);
@@ -5398,7 +5398,7 @@ export function attach(
       rootToFiberInstanceMap.set(root, rootInstance);
       idToDevToolsInstanceMap.set(rootInstance.id, rootInstance);
     } else {
-      prevFiber = rootInstance.data.alternate;
+      prevFiber = rootInstance.data;
     }
     currentRoot = rootInstance;
 
@@ -5452,6 +5452,9 @@ export function attach(
       unmountInstanceRecursively(rootInstance);
       removeRootPseudoKey(currentRoot.id);
       rootToFiberInstanceMap.delete(root);
+    } else if (!prevWasMounted && !nextIsMounted) {
+      // We don't need this root anymore.
+      rootToFiberInstanceMap.delete(root);
     }
 
     if (isProfiling && isProfilingSupported) {
@@ -5475,7 +5478,7 @@ export function attach(
     }
 
     // We're done here.
-    flushPendingEvents(root);
+    flushPendingEvents();
 
     needsToFlushComponentLogs = false;