[kbn/optimizer] require fsevents on macos (#67147)

packages/kbn-optimizer/src/run_optimizer.ts

@@ -39,10 +39,26 @@ export type OptimizerUpdate = Update<OptimizerEvent, OptimizerState>;
 export type OptimizerUpdate$ = Rx.Observable<OptimizerUpdate>;
 
 export function runOptimizer(config: OptimizerConfig) {
-  return Rx.defer(async () => ({
-    startTime: Date.now(),
-    cacheKey: await getOptimizerCacheKey(config),
-  })).pipe(
+  return Rx.defer(async () => {
+    if (process.platform === 'darwin') {
+      try {
+        require.resolve('fsevents');
+      } catch (error) {
+        if (error.code === 'MODULE_NOT_FOUND') {
+          throw new Error(
+            '`fsevents` module is not installed, most likely because you need to follow the instructions at https://github.com/nodejs/node-gyp/blob/master/macOS_Catalina.md and re-bootstrap Kibana'
+          );
+        }
+
+        throw error;
+      }
+    }
+
+    return {
+      startTime: Date.now(),
+      cacheKey: await getOptimizerCacheKey(config),
+    };
+  }).pipe(
     mergeMap(({ startTime, cacheKey }) => {
       const bundleCacheEvent$ = getBundleCacheEvent$(config, cacheKey).pipe(
         observeOn(Rx.asyncScheduler),