fix: optimize userEvent.type performance by filtering eventWrapper from instrumentation

Add getKeys filter to exclude 'eventWrapper' property from instrumenter calls to prevent performance regression in userEvent.type operations. This addresses the slowdown reported when upgrading from Storybook 8 to 9 with addon-vitest.

The instrumenter was spending significant time sorting large arrays of calls that included the eventWrapper property, which is not needed for testing interactions. By filtering it out at the instrumentation level, we avoid unnecessary processing overhead.

Author: ndelangen

code/core/src/test/preview.ts

@@ -96,7 +96,10 @@ const enhanceContext: LoaderFunction = async (context) => {
   if (clipboard) {
     context.userEvent = instrument(
       { userEvent: uninstrumentedUserEvent.setup() },
-      { intercept: true }
+      {
+        intercept: true,
+        getKeys: (obj) => Object.keys(obj).filter((key) => key !== 'eventWrapper'),
+      }
     ).userEvent;
 
     // Restore original clipboard, which was replaced with a stub by userEvent.setup()

code/core/src/test/testing-library.ts

@@ -15,6 +15,7 @@ type TestingLibraryDom = typeof domTestingLibrary;
 const testingLibrary = instrument(
   { ...domTestingLibrary },
   {
+    getKeys: (obj) => Object.keys(obj).filter((key) => key !== 'eventWrapper'),
     intercept: (method, path) =>
       path[0] === 'fireEvent' || method.startsWith('find') || method.startsWith('waitFor'),
   }
@@ -118,5 +119,5 @@ export const uninstrumentedUserEvent = _userEvent.userEvent;
 
 export const { userEvent }: { userEvent: UserEvent['userEvent'] } = instrument(
   { userEvent: _userEvent.userEvent },
-  { intercept: true }
+  { intercept: true, getKeys: (obj) => Object.keys(obj).filter((key) => key !== 'eventWrapper') }
 );