Wait for preload scripts before loading renderers (microsoft#164406)

src/vs/workbench/contrib/notebook/browser/view/renderers/webviewPreloads.ts

@@ -1320,13 +1320,15 @@ async function webviewPreloads(ctx: PreloadContext) {
 
 		/** Inner function cached in the _loadPromise(). */
 		private async _load(): Promise<rendererApi.RendererApi | undefined> {
+			// Preloads need to be loaded before loading renderers.
+			await kernelPreloads.waitForAllCurrent();
+
 			const module: RendererModule = await __import(this.data.entrypoint.path);
 			if (!module) {
 				return;
 			}
 
 			this._api = await module.activate(this.createRendererContext());
-
 			// Load all renderers that extend this renderer
 			await Promise.all(
 				ctx.rendererData
@@ -1380,7 +1382,7 @@ async function webviewPreloads(ctx: PreloadContext) {
 		 * Returns a promise that waits for all currently-registered preloads to
 		 * activate before resolving.
 		 */
-		private waitForAllCurrent() {
+		public waitForAllCurrent() {
 			return Promise.all([...this.preloads.values()].map(p => p.catch(err => err)));
 		}
 	};