Re #96398. Fix the data loss when switching

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

@@ -102,6 +102,7 @@ export interface ICellViewModel {
 	currentTokenSource: CancellationTokenSource | undefined;
 	focusMode: CellFocusMode;
 	getText(): string;
+	save(): void;
 	metadata: NotebookCellMetadata | undefined;
 	getEvaluatedMetadata(documentMetadata: NotebookDocumentMetadata | undefined): NotebookCellMetadata;
 }

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

@@ -636,6 +636,8 @@ export class NotebookEditor extends BaseEditor implements INotebookEditor {
 
 			state.contributionsState = contributionsState;
 			this.editorMemento.saveEditorState(this.group, input.resource, state);
+
+			this.notebookViewModel.viewCells.forEach(cell => cell.save());
 		}
 	}
 

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

@@ -173,6 +173,10 @@ export class NotebookEditorInput extends EditorInput {
 	}
 
 	async resolve(): Promise<NotebookEditorModel> {
+		if (this.textModel) {
+			return this.textModel;
+		}
+
 		if (!this.promise) {
 			if (!await this.notebookService.canResolve(this.viewType!)) {
 				throw new Error(`Cannot open notebook of type '${this.viewType}'`);

src/vs/workbench/contrib/notebook/browser/viewModel/baseCellViewModel.ts

@@ -199,6 +199,8 @@ export abstract class BaseCellViewModel extends Disposable implements ICellViewM
 		return this.model.source.join('\n');
 	}
 
+	abstract save(): void;
+
 	private saveViewState(): editorCommon.ICodeEditorViewState | null {
 		if (!this._textEditor) {
 			return null;