Enable restoring a selected kernel that is not yet registered

Fix #171385

src/vs/workbench/contrib/notebook/browser/notebookEditorWidget.ts

@@ -1640,13 +1640,7 @@ export class NotebookEditorWidget extends Disposable implements INotebookEditorD
 
 	private _restoreSelectedKernel(viewState: INotebookEditorViewState | undefined): void {
 		if (viewState?.selectedKernelId && this.textModel) {
-			const matching = this.notebookKernelService.getMatchingKernel(this.textModel);
-			const kernel = matching.all.find(k => k.id === viewState.selectedKernelId);
-			// Selected kernel may have already been picked prior to the view state loading
-			// If so, don't overwrite it with the saved kernel.
-			if (kernel && !matching.selected) {
-				this.notebookKernelService.selectKernelForNotebook(kernel, this.textModel);
-			}
+			this.notebookKernelService.restoreKernelIdForNotebook(viewState.selectedKernelId, this.textModel);
 		}
 	}
 

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

@@ -282,6 +282,16 @@ export class NotebookKernelService extends Disposable implements INotebookKernel
 		}
 	}
 
+	restoreKernelIdForNotebook(kernelId: string, notebook: INotebookTextModelLike): void {
+		const key = NotebookTextModelLikeId.str(notebook);
+		const oldKernel = this._notebookBindings.get(key);
+		if (!oldKernel) {
+			this._notebookBindings.set(key, kernelId);
+			this._onDidChangeNotebookKernelBinding.fire({ notebook: notebook.uri, oldKernel, newKernel: kernelId });
+			this._persistMementos();
+		}
+	}
+
 	preselectKernelForNotebook(kernel: INotebookKernel, notebook: INotebookTextModelLike): void {
 		const key = NotebookTextModelLikeId.str(notebook);
 		const oldKernel = this._notebookBindings.get(key);

src/vs/workbench/contrib/notebook/common/notebookKernelService.ts

@@ -117,6 +117,12 @@ export interface INotebookKernelService {
 	 */
 	selectKernelForNotebook(kernel: INotebookKernel, notebook: INotebookTextModelLike): void;
 
+	/**
+	 * Restore a previously selected kernel id. The kernel may or may not be registered yet
+	 * when this is called.
+	 */
+	restoreKernelIdForNotebook(kernelId: string, notebook: INotebookTextModelLike): void;
+
 	/**
 	 * Set the kernel that a notebook should use when it starts up
 	 */