No prompt to install Python when open an exist nb without Kernel

src/client/datascience/jupyter/kernels/helpers.ts

@@ -339,8 +339,9 @@ export function findPreferredKernel(
 
     // If still not found, look for a match based on notebook metadata and interpreter
     if (index < 0) {
+        const hasLanguageInfo = notebookMetadata?.language_info?.name ? true : false;
         const nbMetadataLanguage =
-            !notebookMetadata || isPythonNotebook(notebookMetadata)
+            !notebookMetadata || isPythonNotebook(notebookMetadata) || !hasLanguageInfo
                 ? PYTHON_LANGUAGE
                 : (
                       (notebookMetadata?.kernelspec?.language as string) || notebookMetadata?.language_info?.name

src/client/datascience/notebook/defaultCellLanguageService.ts

@@ -7,6 +7,7 @@ import type { nbformat } from '@jupyterlab/coreutils/lib/nbformat';
 import { inject, injectable, named } from 'inversify';
 import { Memento, NotebookCellKind, NotebookDocument } from 'vscode';
 import { IExtensionSingleActivationService } from '../../activation/types';
+import { IPythonExtensionChecker } from '../../api/types';
 import { IVSCodeNotebook } from '../../common/application/types';
 import { PYTHON_LANGUAGE } from '../../common/constants';
 import { traceWarning } from '../../common/logger';
@@ -27,6 +28,7 @@ export class NotebookCellLanguageService implements IExtensionSingleActivationSe
     constructor(
         @inject(IVSCodeNotebook) private readonly vscNotebook: IVSCodeNotebook,
         @inject(IDisposableRegistry) private readonly disposables: IDisposableRegistry,
+        @inject(IPythonExtensionChecker) private readonly pythonExtensionChecker: IPythonExtensionChecker,
         @inject(IMemento) @named(GLOBAL_MEMENTO) private readonly globalMemento: Memento
     ) {}
     /**
@@ -38,7 +40,11 @@ export class NotebookCellLanguageService implements IExtensionSingleActivationSe
             metadata?.language_info?.name ||
             (metadata?.kernelspec as IJupyterKernelSpec | undefined)?.language ||
             this.lastSavedNotebookCellLanguage;
-        return translateKernelLanguageToMonaco(jupyterLanguage || PYTHON_LANGUAGE);
+
+        // Default to python language only if the Python extension is installed.
+        const defaultLanguage = this.pythonExtensionChecker.isPythonExtensionInstalled ? PYTHON_LANGUAGE : 'plaintext';
+        // Note, what ever language is returned here, when the user selects a kernel, the cells (of blank documents) get updated based on that kernel selection.
+        return translateKernelLanguageToMonaco(jupyterLanguage || defaultLanguage);
     }
     public async activate() {
         this.vscNotebook.onDidSaveNotebookDocument(this.onDidSaveNotebookDocument, this, this.disposables);

src/client/datascience/notebook/helpers/helpers.ts

@@ -107,11 +107,8 @@ export function isPythonNotebook(metadata?: nbformat.INotebookMetadata) {
     if (metadata?.language_info?.name && metadata.language_info.name !== PYTHON_LANGUAGE) {
         return false;
     }
-    if (kernelSpec?.language && kernelSpec.language !== PYTHON_LANGUAGE) {
-        return false;
-    }
-    // All other notebooks are python notebooks.
-    return true;
+    // Valid notebooks will have a language information in the metadata.
+    return kernelSpec?.language === PYTHON_LANGUAGE;
 }
 /**
  * No need to update the notebook metadata just yet.

src/client/datascience/notebook/kernelWithMetadata.ts

@@ -3,7 +3,7 @@
 
 // eslint-disable-next-line @typescript-eslint/no-require-imports
 import { join } from 'path';
-import { Uri, NotebookCell, NotebookDocument, NotebookKernel as VSCNotebookKernel } from 'vscode';
+import { Uri, NotebookCell, NotebookDocument, NotebookKernel as VSCNotebookKernel, notebook } from 'vscode';
 import { ICommandManager, IVSCodeNotebook } from '../../common/application/types';
 import { disposeAllDisposables } from '../../common/helpers';
 import { traceInfo } from '../../common/logger';
@@ -16,6 +16,7 @@ import { KernelSocketInformation } from '../types';
 import { traceCellMessage, trackKernelInfoInNotebookMetadata } from './helpers/helpers';
 
 export class VSCodeNotebookKernelMetadata implements VSCNotebookKernel {
+    private notebookKernels = new WeakMap<NotebookDocument, IKernel>();
     get preloads(): Uri[] {
         return [
             Uri.file(join(this.context.extensionPath, 'out', 'ipywidgets', 'dist', 'ipywidgets.js')),
@@ -64,18 +65,29 @@ export class VSCodeNotebookKernelMetadata implements VSCNotebookKernel {
         this.commandManager.executeCommand(Commands.NotebookEditorInterruptKernel).then(noop, noop);
     }
     private updateKernelInfoInNotebookWhenAvailable(kernel: IKernel, doc: NotebookDocument) {
+        if (this.notebookKernels.get(doc) === kernel) {
+            return;
+        }
+        this.notebookKernels.set(doc, kernel);
         let kernelSocket: KernelSocketInformation | undefined;
         const handlerDisposables: IDisposable[] = [];
-
+        // If the notebook is closed, dispose everything.
+        notebook.onDidCloseNotebookDocument(
+            (e) => {
+                if (e === doc) {
+                    disposeAllDisposables(handlerDisposables);
+                }
+            },
+            this,
+            handlerDisposables
+        );
         const saveKernelInfo = () => {
             const kernelId = kernelSocket?.options.id;
             if (!kernelId) {
                 return;
             }
             traceInfo(`Updating preferred kernel for remote notebook ${kernelId}`);
             this.preferredRemoteKernelIdProvider.storePreferredRemoteKernelId(doc.uri, kernelId).catch(noop);
-
-            disposeAllDisposables(handlerDisposables);
         };
 
         const kernelDisposedDisposable = kernel.onDisposed(() => disposeAllDisposables(handlerDisposables));
@@ -92,8 +104,14 @@ export class VSCodeNotebookKernelMetadata implements VSCNotebookKernel {
                 return;
             }
             trackKernelInfoInNotebookMetadata(doc, kernel.info);
-            if (kernel.info.status === 'ok' && this.selection.kind === 'startUsingKernelSpec') {
-                saveKernelInfo();
+            if (this.selection.kind === 'startUsingKernelSpec') {
+                if (kernel.info.status === 'ok') {
+                    saveKernelInfo();
+                } else {
+                    disposeAllDisposables(handlerDisposables);
+                }
+            } else {
+                disposeAllDisposables(handlerDisposables);
             }
         });
 

src/client/datascience/notebookStorage/vscNotebookModel.ts

@@ -83,15 +83,12 @@ export class VSCodeNotebookModel extends BaseNotebookModel {
         return this.document ? this.document.cells.length : this.notebookJson.cells?.length ?? 0;
     }
     public getNotebookData() {
-        if (!this.preferredLanguage) {
-            throw new Error('Preferred Language not initialized');
-        }
         return notebookModelToVSCNotebookData(
             this.isTrusted,
             this.notebookContentWithoutCells,
             this.file,
             this.notebookJson.cells || [],
-            this.preferredLanguage,
+            this.preferredLanguage || 'plaintext',
             this.originalJson
         );
     }

src/client/datascience/openNotebookBanner.ts

@@ -30,7 +30,7 @@ export class OpenNotebookBanner implements IExtensionSingleActivationService {
     private async openedNotebook(editor: INotebookEditor) {
         if (
             !this.pythonExtensionChecker.isPythonExtensionInstalled &&
-            editor.model.metadata &&
+            editor.model.metadata?.kernelspec &&
             isPythonNotebook(editor.model.metadata) &&
             !isUntitledFile(editor.file)
         ) {