fix: hash venv name

Author: saltenasl

DEEPNOTE_KERNEL_IMPLEMENTATION.md

@@ -35,7 +35,7 @@ This implementation adds automatic kernel selection and startup for `.deepnote`
 **Key Methods:**
 - `getVenvInterpreter(deepnoteFileUri)`: Gets the venv Python interpreter for a specific file
 - `ensureInstalled(interpreter, deepnoteFileUri)`: Creates venv, installs toolkit and ipykernel, and registers kernel spec
-- `getVenvHash(deepnoteFileUri)`: Creates a unique hash for kernel naming
+- `getVenvHash(deepnoteFileUri)`: Creates a unique hash for both kernel naming and venv directory paths
 - `getDisplayName(deepnoteFileUri)`: Gets a friendly display name for the kernel
 
 #### 3. **Deepnote Server Starter** (`src/kernels/deepnote/deepnoteServerStarter.node.ts`)
@@ -155,7 +155,7 @@ User runs cell → Executes on Deepnote kernel
 - **Wheel URL**: `https://deepnote-staging-runtime-artifactory.s3.amazonaws.com/deepnote-toolkit-packages/0.2.30.post20/deepnote_toolkit-0.2.30.post20-py3-none-any.whl`
 - **Default Port**: `8888` (will find next available if occupied)
 - **Notebook Type**: `deepnote`
-- **Venv Location**: `~/.vscode/extensions/storage/deepnote-venvs/<file-path-hash>/`
+- **Venv Location**: `~/.vscode/extensions/storage/deepnote-venvs/<hashed-path>/` (e.g., `venv_a1b2c3d4`)
 - **Server Provider ID**: `deepnote-server`
 - **Kernel Spec Name**: `deepnote-venv-<file-path-hash>` (registered via ipykernel to point to venv Python)
 - **Kernel Display Name**: `Deepnote (<notebook-filename>)`
@@ -302,6 +302,19 @@ Instead of creating custom kernel specs, the implementation:
 4. Uses this existing spec when creating the kernel connection metadata
 5. This ensures compatibility with the Deepnote server's kernel configuration
 
+### Virtual Environment Path Handling
+
+The implementation uses a robust hashing approach for virtual environment directory names:
+
+1. **Path Hashing**: Uses `getVenvHash()` to create short, unique identifiers from file paths
+2. **Hash Algorithm**: Implements a djb2-style hash function for better distribution
+3. **Format**: Generates identifiers like `venv_a1b2c3d4` (max 16 characters)
+4. **Benefits**:
+   - Avoids Windows MAX_PATH (260 character) limitations
+   - Prevents directory structure leakage into extension storage
+   - Provides consistent naming for both venv directories and kernel specs
+   - Reduces collision risk with better hash distribution
+
 ## Troubleshooting & Key Fixes
 
 ### Issue 1: "Unable to get resolved server information"

src/kernels/deepnote/deepnoteToolkitInstaller.node.ts

@@ -29,10 +29,10 @@ export class DeepnoteToolkitInstaller implements IDeepnoteToolkitInstaller {
     ) {}
 
     private getVenvPath(deepnoteFileUri: Uri): Uri {
-        // Create a unique venv name based on the file path
-        // Use a simple hash approach - replace special chars with underscores
-        const safePath = deepnoteFileUri.fsPath.replace(/[^a-zA-Z0-9]/g, '_');
-        return Uri.joinPath(this.context.globalStorageUri, 'deepnote-venvs', safePath);
+        // Create a unique venv name based on the file path using a hash
+        // This avoids Windows MAX_PATH issues and prevents directory structure leakage
+        const hash = this.getVenvHash(deepnoteFileUri);
+        return Uri.joinPath(this.context.globalStorageUri, 'deepnote-venvs', hash);
     }
 
     public async getVenvInterpreter(deepnoteFileUri: Uri): Promise<PythonEnvironment | undefined> {
@@ -240,9 +240,21 @@ export class DeepnoteToolkitInstaller implements IDeepnoteToolkitInstaller {
     }
 
     private getVenvHash(deepnoteFileUri: Uri): string {
-        // Create a short hash from the file path for kernel naming
-        const safePath = deepnoteFileUri.fsPath.replace(/[^a-zA-Z0-9]/g, '_');
-        return safePath.substring(0, 16); // Limit length
+        // Create a short hash from the file path for kernel naming and venv directory
+        // This provides better uniqueness and prevents directory structure leakage
+        const path = deepnoteFileUri.fsPath;
+
+        // Use a simple hash function for better distribution
+        let hash = 0;
+        for (let i = 0; i < path.length; i++) {
+            const char = path.charCodeAt(i);
+            hash = (hash << 5) - hash + char;
+            hash = hash & hash; // Convert to 32-bit integer
+        }
+
+        // Convert to positive hex string and limit length
+        const hashStr = Math.abs(hash).toString(16);
+        return `venv_${hashStr}`.substring(0, 16);
     }
 
     private getDisplayName(deepnoteFileUri: Uri): string {