EditorInput/NotebookTextModel is N/1 mapping.

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

@@ -94,7 +94,9 @@ Registry.as<IEditorInputFactoryRegistry>(EditorInputExtensions.EditorInputFactor
 				return undefined;
 			}
 
-			const input = NotebookEditorInput.getOrCreate(instantiationService, resource, name, viewType);
+			// if we have two editors open with the same resource (in different editor groups), we should then create two different
+			// editor inputs, instead of `getOrCreate`.
+			const input = NotebookEditorInput.create(instantiationService, resource, name, viewType);
 			if (typeof data.group === 'number') {
 				input.updateGroup(data.group);
 			}
@@ -245,7 +247,7 @@ export class NotebookContribution extends Disposable implements IWorkbenchContri
 				const name = basename(data.notebook);
 				let input = this._resourceMapping.get(data.notebook);
 				if (!input || input.isDisposed()) {
-					input = NotebookEditorInput.getOrCreate(this.instantiationService, data.notebook, name, info.id);
+					input = NotebookEditorInput.create(this.instantiationService, data.notebook, name, info.id);
 					this._resourceMapping.set(data.notebook, input);
 				}
 
@@ -261,7 +263,7 @@ export class NotebookContribution extends Disposable implements IWorkbenchContri
 			return undefined;
 		}
 
-		const input = NotebookEditorInput.getOrCreate(this.instantiationService, resource, originalInput.getName(), info.id);
+		const input = NotebookEditorInput.create(this.instantiationService, resource, originalInput.getName(), info.id);
 		input.updateGroup(group.id);
 		this._resourceMapping.set(resource, input);
 

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

@@ -14,23 +14,8 @@ import { IFileDialogService } from 'vs/platform/dialogs/common/dialogs';
 
 let NOTEBOOK_EDITOR_INPUT_HANDLE = 0;
 export class NotebookEditorInput extends EditorInput {
-
-	private static readonly _instances = new Map<string, NotebookEditorInput>();
-
-	static getOrCreate(instantiationService: IInstantiationService, resource: URI, name: string, viewType: string | undefined) {
-		const key = resource.toString() + viewType;
-		let input = NotebookEditorInput._instances.get(key);
-		if (!input) {
-			input = instantiationService.createInstance(class extends NotebookEditorInput {
-				dispose() {
-					NotebookEditorInput._instances.delete(key);
-					super.dispose();
-				}
-			}, resource, name, viewType);
-
-			NotebookEditorInput._instances.set(key, input);
-		}
-		return input;
+	static create(instantiationService: IInstantiationService, resource: URI, name: string, viewType: string | undefined) {
+		return instantiationService.createInstance(NotebookEditorInput, resource, name, viewType);
 	}
 
 	static readonly ID: string = 'workbench.input.notebook';
@@ -132,7 +117,7 @@ export class NotebookEditorInput extends EditorInput {
 	}
 
 	_move(group: GroupIdentifier, newResource: URI): { editor: IEditorInput } | undefined {
-		const editorInput = NotebookEditorInput.getOrCreate(this.instantiationService, newResource, basename(newResource), this.viewType);
+		const editorInput = NotebookEditorInput.create(this.instantiationService, newResource, basename(newResource), this.viewType);
 		return { editor: editorInput };
 	}