Fix notebook serializer activation

Author: joyceerhl

src/vs/workbench/contrib/notebook/browser/services/notebookServiceImpl.ts

@@ -116,13 +116,14 @@ export class NotebookProviderInfoStore extends Disposable {
 					if (!existing.extension && extension.description.isBuiltin && builtins.find(builtin => builtin.id === notebookContribution.type)) {
 						// we are registering an extension which is using the same view type which is already cached
 						builtinProvidersFromCache.get(notebookContribution.type)?.dispose();
-						implicitActivationEvents.push(`onNotebookSerializer:${notebookContribution.type}`);
 					} else {
 						extension.collector.error(`Notebook type '${notebookContribution.type}' already used`);
 						continue;
 					}
 				}
 
+				implicitActivationEvents.push(`onNotebookSerializer:${notebookContribution.type}`);
+
 				this.add(new NotebookProviderInfo({
 					extension: extension.description.identifier,
 					id: notebookContribution.type,

src/vs/workbench/services/extensions/common/abstractExtensionService.ts

@@ -1226,6 +1226,7 @@ export abstract class AbstractExtensionService extends Disposable implements IEx
 		}
 		this._combineImplicitExtensionActivationEvents();
 		perf.mark('code/didHandleExtensionPoints');
+		this._registry.set(availableExtensions);
 	}
 
 	private _combineImplicitExtensionActivationEvents() {