feat: Better error messages when installing the Deepnote kernel.

src/kernels/deepnote/deepnoteServerStarter.node.ts

@@ -17,6 +17,7 @@ import * as fs from 'fs-extra';
 import * as os from 'os';
 import * as path from '../../platform/vscode-path/path';
 import { generateUuid } from '../../platform/common/uuid';
+import { DeepnoteServerStartupError, DeepnoteServerTimeoutError } from '../../platform/errors/deepnoteKernelErrors';
 
 /**
  * Lock file data structure for tracking server ownership
@@ -41,6 +42,8 @@ export class DeepnoteServerStarter implements IDeepnoteServerStarter, IExtension
     private readonly sessionId: string = generateUuid();
     // Directory for lock files
     private readonly lockFileDir: string = path.join(os.tmpdir(), 'vscode-deepnote-locks');
+    // Track server output for error reporting
+    private readonly serverOutputByFile: Map<string, { stdout: string; stderr: string }> = new Map();
 
     constructor(
         @inject(IProcessServiceFactory) private readonly processServiceFactory: IProcessServiceFactory,
@@ -175,15 +178,27 @@ export class DeepnoteServerStarter implements IDeepnoteServerStarter, IExtension
         const disposables: IDisposable[] = [];
         this.disposablesByFile.set(fileKey, disposables);
 
+        // Initialize output tracking for error reporting
+        this.serverOutputByFile.set(fileKey, { stdout: '', stderr: '' });
+
         // Monitor server output
         serverProcess.out.onDidChange(
             (output) => {
+                const outputTracking = this.serverOutputByFile.get(fileKey);
                 if (output.source === 'stdout') {
                     logger.trace(`Deepnote server (${fileKey}): ${output.out}`);
                     this.outputChannel.appendLine(output.out);
+                    if (outputTracking) {
+                        // Keep last 5000 characters of output for error reporting
+                        outputTracking.stdout = (outputTracking.stdout + output.out).slice(-5000);
+                    }
                 } else if (output.source === 'stderr') {
                     logger.warn(`Deepnote server stderr (${fileKey}): ${output.out}`);
                     this.outputChannel.appendLine(output.out);
+                    if (outputTracking) {
+                        // Keep last 5000 characters of error output for error reporting
+                        outputTracking.stderr = (outputTracking.stderr + output.out).slice(-5000);
+                    }
                 }
             },
             this,
@@ -206,13 +221,30 @@ export class DeepnoteServerStarter implements IDeepnoteServerStarter, IExtension
         try {
             const serverReady = await this.waitForServer(serverInfo, 120000, token);
             if (!serverReady) {
+                const output = this.serverOutputByFile.get(fileKey);
                 await this.stopServerImpl(deepnoteFileUri);
-                throw new Error('Deepnote server failed to start within timeout period');
+
+                throw new DeepnoteServerTimeoutError(serverInfo.url, 120000, output?.stderr || undefined);
             }
         } catch (error) {
             // Clean up leaked server before rethrowing
             await this.stopServerImpl(deepnoteFileUri);
-            throw error;
+
+            // If this is already a DeepnoteKernelError, rethrow it
+            if (error instanceof DeepnoteServerTimeoutError || error instanceof DeepnoteServerStartupError) {
+                throw error;
+            }
+
+            // Otherwise wrap in a generic server startup error
+            const output = this.serverOutputByFile.get(fileKey);
+            throw new DeepnoteServerStartupError(
+                interpreter.uri.fsPath,
+                port,
+                'unknown',
+                output?.stdout || '',
+                output?.stderr || '',
+                error instanceof Error ? error : undefined
+            );
         }
 
         logger.info(`Deepnote server started successfully at ${url} for ${fileKey}`);
@@ -261,6 +293,7 @@ export class DeepnoteServerStarter implements IDeepnoteServerStarter, IExtension
                 serverProcess.proc?.kill();
                 this.serverProcesses.delete(fileKey);
                 this.serverInfos.delete(fileKey);
+                this.serverOutputByFile.delete(fileKey);
                 this.outputChannel.appendLine(`Deepnote server stopped for ${fileKey}`);
 
                 // Clean up lock file after stopping the server
@@ -381,6 +414,7 @@ export class DeepnoteServerStarter implements IDeepnoteServerStarter, IExtension
         this.serverInfos.clear();
         this.disposablesByFile.clear();
         this.pendingOperations.clear();
+        this.serverOutputByFile.clear();
 
         logger.info('DeepnoteServerStarter disposed successfully');
     }

src/kernels/deepnote/deepnoteToolkitInstaller.node.ts

@@ -11,6 +11,7 @@ import { IOutputChannel, IExtensionContext } from '../../platform/common/types';
 import { STANDARD_OUTPUT_CHANNEL } from '../../platform/common/constants';
 import { IFileSystem } from '../../platform/common/platform/types';
 import { Cancellation } from '../../platform/common/cancellation';
+import { DeepnoteVenvCreationError, DeepnoteToolkitInstallError } from '../../platform/errors/deepnoteKernelErrors';
 
 /**
  * Handles installation of the deepnote-toolkit Python package.
@@ -158,7 +159,12 @@ export class DeepnoteToolkitInstaller implements IDeepnoteToolkitInstaller {
                     logger.error(`venv stderr: ${venvResult.stderr}`);
                 }
                 this.outputChannel.appendLine('Error: Failed to create virtual environment');
-                return undefined;
+
+                throw new DeepnoteVenvCreationError(
+                    baseInterpreter.uri.fsPath,
+                    venvPath.fsPath,
+                    venvResult.stderr || 'Virtual environment was created but Python interpreter not found'
+                );
             }
 
             // Use undefined as resource to get full system environment (including git in PATH)
@@ -250,12 +256,33 @@ export class DeepnoteToolkitInstaller implements IDeepnoteToolkitInstaller {
             } else {
                 logger.error('deepnote-toolkit installation failed');
                 this.outputChannel.appendLine('✗ deepnote-toolkit installation failed');
-                return undefined;
+
+                throw new DeepnoteToolkitInstallError(
+                    venvInterpreter.uri.fsPath,
+                    venvPath.fsPath,
+                    DEEPNOTE_TOOLKIT_WHEEL_URL,
+                    installResult.stdout || '',
+                    installResult.stderr || 'Package installation completed but verification failed'
+                );
             }
         } catch (ex) {
+            // If this is already a DeepnoteKernelError, rethrow it without wrapping
+            if (ex instanceof DeepnoteVenvCreationError || ex instanceof DeepnoteToolkitInstallError) {
+                throw ex;
+            }
+
+            // Otherwise, log and wrap in a generic toolkit install error
             logger.error(`Failed to set up deepnote-toolkit: ${ex}`);
             this.outputChannel.appendLine(`Error setting up deepnote-toolkit: ${ex}`);
-            return undefined;
+
+            throw new DeepnoteToolkitInstallError(
+                baseInterpreter.uri.fsPath,
+                venvPath.fsPath,
+                DEEPNOTE_TOOLKIT_WHEEL_URL,
+                '',
+                ex instanceof Error ? ex.message : String(ex),
+                ex instanceof Error ? ex : undefined
+            );
         }
     }
 

src/notebooks/deepnote/deepnoteKernelAutoSelector.node.ts

@@ -1,7 +1,7 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
 
-import { inject, injectable, optional } from 'inversify';
+import { inject, injectable, optional, named } from 'inversify';
 import {
     CancellationToken,
     NotebookDocument,
@@ -13,7 +13,8 @@ import {
     NotebookController,
     CancellationTokenSource,
     Disposable,
-    l10n
+    l10n,
+    env
 } from 'vscode';
 import { IExtensionSyncActivationService } from '../../platform/activation/types';
 import { IDisposableRegistry } from '../../platform/common/types';
@@ -42,6 +43,9 @@ import { IDeepnoteNotebookManager } from '../types';
 import { IDeepnoteRequirementsHelper } from './deepnoteRequirementsHelper.node';
 import { DeepnoteProject } from './deepnoteTypes';
 import { IKernelProvider, IKernel } from '../../kernels/types';
+import { DeepnoteKernelError } from '../../platform/errors/deepnoteKernelErrors';
+import { STANDARD_OUTPUT_CHANNEL } from '../../platform/common/constants';
+import { IOutputChannel } from '../../platform/common/types';
 
 /**
  * Automatically selects and starts Deepnote kernel for .deepnote notebooks
@@ -78,7 +82,8 @@ export class DeepnoteKernelAutoSelector implements IDeepnoteKernelAutoSelector,
         @inject(IDeepnoteInitNotebookRunner) private readonly initNotebookRunner: IDeepnoteInitNotebookRunner,
         @inject(IDeepnoteNotebookManager) private readonly notebookManager: IDeepnoteNotebookManager,
         @inject(IKernelProvider) private readonly kernelProvider: IKernelProvider,
-        @inject(IDeepnoteRequirementsHelper) private readonly requirementsHelper: IDeepnoteRequirementsHelper
+        @inject(IDeepnoteRequirementsHelper) private readonly requirementsHelper: IDeepnoteRequirementsHelper,
+        @inject(IOutputChannel) @named(STANDARD_OUTPUT_CHANNEL) private readonly outputChannel: IOutputChannel
     ) {}
 
     public activate() {
@@ -129,9 +134,7 @@ export class DeepnoteKernelAutoSelector implements IDeepnoteKernelAutoSelector,
         // Don't await - let it happen in background so notebook opens quickly
         void this.ensureKernelSelected(notebook).catch((error) => {
             logger.error(`Failed to auto-select Deepnote kernel for ${getDisplayPath(notebook.uri)}`, error);
-            void window.showErrorMessage(
-                l10n.t('Failed to load Deepnote kernel. Please check the output for details.')
-            );
+            void this.handleKernelSelectionError(error);
         });
     }
 
@@ -553,4 +556,50 @@ export class DeepnoteKernelAutoSelector implements IDeepnoteKernelAutoSelector,
         this.loadingControllers.set(notebookKey, loadingController);
         logger.info(`Created loading controller for ${notebookKey}`);
     }
+
+    /**
+     * Handle kernel selection errors with user-friendly messages and actions
+     */
+    private async handleKernelSelectionError(error: unknown): Promise<void> {
+        // Handle DeepnoteKernelError types with specific guidance
+        if (error instanceof DeepnoteKernelError) {
+            // Log the technical details
+            logger.error(error.getErrorReport());
+
+            // Show user-friendly error with actions
+            const actions: string[] = ['Show Output', 'Copy Error Details'];
+
+            const selectedAction = await window.showErrorMessage(
+                `${error.userMessage}\n\nTroubleshooting:\n${error.troubleshootingSteps
+                    .slice(0, 3)
+                    .map((step, i) => `${i + 1}. ${step}`)
+                    .join('\n')}`,
+                { modal: false },
+                ...actions
+            );
+
+            if (selectedAction === 'Show Output') {
+                this.outputChannel.show();
+            } else if (selectedAction === 'Copy Error Details') {
+                await env.clipboard.writeText(error.getErrorReport());
+                void window.showInformationMessage('Error details copied to clipboard');
+            }
+
+            return;
+        }
+
+        // Handle generic errors
+        const errorMessage = error instanceof Error ? error.message : String(error);
+        logger.error(`Deepnote kernel error: ${errorMessage}`);
+
+        const selectedAction = await window.showErrorMessage(
+            l10n.t('Failed to load Deepnote kernel: {0}', errorMessage),
+            { modal: false },
+            'Show Output'
+        );
+
+        if (selectedAction === 'Show Output') {
+            this.outputChannel.show();
+        }
+    }
 }