Fix local nbextensions path resolution for kernels launched from local kernelspecs

src/notebooks/controllers/ipywidgets/scriptSourceProvider/nbExtensionsPathProvider.node.ts

@@ -25,6 +25,18 @@ export class NbExtensionsPathProvider implements INbExtensionsPathProvider {
                 }
                 return Uri.joinPath(Uri.file(sysPrefix), 'share', 'jupyter');
             }
+            case 'startUsingLocalKernelSpec': {
+                // If this local kernelspec has an associated Python interpreter, use its sysPrefix
+                if (kernel.kernelConnectionMetadata.interpreter) {
+                    const sysPrefix = await getSysPrefix(kernel.kernelConnectionMetadata.interpreter);
+                    if (!sysPrefix) {
+                        return;
+                    }
+                    return Uri.joinPath(Uri.file(sysPrefix), 'share', 'jupyter');
+                }
+                // If no interpreter is associated, we can't determine the nbextensions path
+                return;
+            }
             default: {
                 // We haven't come across scenarios with non-python kernels that use widgets
                 // & have custom widget sources. If we do, we can implement that as we come across them.

src/notebooks/controllers/ipywidgets/scriptSourceProvider/nbExtensionsPathProvider.unit.test.ts

@@ -36,6 +36,17 @@ import { dispose } from '../../../../platform/common/utils/lifecycle';
             id: 'interpreterId'
         } as any
     });
+    const localKernelSpecWithInterpreter = LocalKernelSpecConnectionMetadata.create({
+        id: 'localKernelSpecWithInterpreter',
+        kernelSpec: mock<IJupyterKernelSpec>(),
+        interpreter: {
+            id: 'interpreterIdForKernelSpec'
+        } as any
+    });
+    const localKernelSpecWithoutInterpreter = LocalKernelSpecConnectionMetadata.create({
+        id: 'localKernelSpecWithoutInterpreter',
+        kernelSpec: mock<IJupyterKernelSpec>()
+    });
     const serverProviderHandle = { handle: 'handle', id: 'id', extensionId: '' };
     const remoteKernelSpec = RemoteKernelSpecConnectionMetadata.create({
         id: '',
@@ -64,6 +75,9 @@ import { dispose } from '../../../../platform/common/utils/lifecycle';
             when(environments.resolveEnvironment(localPythonKernelSpec.interpreter.id)).thenResolve({
                 executable: { sysPrefix: __dirname }
             } as any);
+            when(environments.resolveEnvironment(localKernelSpecWithInterpreter.interpreter!.id)).thenResolve({
+                executable: { sysPrefix: __dirname }
+            } as any);
         });
         teardown(() => {
             disposables = dispose(disposables);
@@ -92,5 +106,19 @@ import { dispose } from '../../../../platform/common/utils/lifecycle';
             const baseUrl = await provider.getNbExtensionsParentPath(instance(kernel));
             assert.strictEqual(baseUrl?.toString(), Uri.parse(remoteLiveKernel.baseUrl).toString());
         });
+        test('Returns base url for local kernelspec with interpreter', async () => {
+            when(kernel.kernelConnectionMetadata).thenReturn(localKernelSpecWithInterpreter);
+            const baseUrl = await provider.getNbExtensionsParentPath(instance(kernel));
+            if (isWeb) {
+                assert.isUndefined(baseUrl);
+            } else {
+                assert.strictEqual(baseUrl?.toString(), Uri.file(path.join(__dirname, 'share', 'jupyter')).toString());
+            }
+        });
+        test('Returns undefined for local kernelspec without interpreter', async () => {
+            when(kernel.kernelConnectionMetadata).thenReturn(localKernelSpecWithoutInterpreter);
+            const baseUrl = await provider.getNbExtensionsParentPath(instance(kernel));
+            assert.isUndefined(baseUrl);
+        });
     });
 });

src/notebooks/controllers/ipywidgets/scriptSourceProvider/nbExtensionsPathProvider.web.ts

@@ -17,8 +17,11 @@ export class NbExtensionsPathProvider implements INbExtensionsPathProvider {
             case 'startUsingRemoteKernelSpec': {
                 return Uri.parse(kernel.kernelConnectionMetadata.baseUrl);
             }
+            case 'startUsingPythonInterpreter':
+            case 'startUsingLocalKernelSpec':
             default: {
                 // Not possible a possible code path in web.
+                // In web environment, only remote kernels are supported.
                 return;
             }
         }