Fix Add Python Project via context menu to directly add file/folder (#431)

## Issue

When right-clicking on a folder or file in the file explorer and
selecting "Add Python Project", the extension shows a quick pick menu
(Auto Find, Select Existing, Create New) instead of directly adding the
selected folder/file to the Python Projects view. This prevents users
from easily adding a single file directly.

## Testing

Verified that:
- Right-clicking on a folder and selecting "Add Python Project" directly
adds that folder
- Right-clicking on a Python file and selecting "Add Python Project"
directly adds that file
- Using the "Add Python Project" button in the Python Projects view
still shows the quick pick UI

Fixes #385. (edit by @eleanorjboyd so it's useful / relevant)

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: eleanorjboyd <[email protected]>

Author: Copilot

src/features/creators/existingProjects.ts

@@ -15,25 +15,35 @@ export class ExistingProjects implements PythonProjectCreator {
     async create(
         _options?: PythonProjectCreatorOptions,
     ): Promise<PythonProject | PythonProject[] | Uri | Uri[] | undefined> {
-        const results = await showOpenDialog({
-            canSelectFiles: true,
-            canSelectFolders: true,
-            canSelectMany: true,
-            filters: {
-                python: ['py'],
-            },
-            title: ProjectCreatorString.selectFilesOrFolders,
-        });
+        let existingAddUri: Uri[] | undefined;
+        if (_options?.rootUri) {
+            // If rootUri is provided, do not prompt
+            existingAddUri = [_options.rootUri];
+        } else if (_options?.quickCreate) {
+            // If quickCreate is true & no rootUri is provided, we should not prompt for any input
+            throw new Error('Root URI is required in quickCreate mode.');
+        } else {
+            // Prompt the user to select files or folders
+            existingAddUri = await showOpenDialog({
+                canSelectFiles: true,
+                canSelectFolders: true,
+                canSelectMany: true,
+                filters: {
+                    python: ['py'],
+                },
+                title: ProjectCreatorString.selectFilesOrFolders,
+            });
+        }
 
-        if (!results || results.length === 0) {
+        if (!existingAddUri || existingAddUri.length === 0) {
             // User cancelled the dialog & doesn't want to add any projects
             return;
         }
 
         // do we have any limitations that need to be applied here?
         // like selected folder not child of workspace folder?
 
-        const filtered = results.filter((uri) => {
+        const filtered = existingAddUri.filter((uri) => {
             const p = this.pm.get(uri);
             if (p) {
                 // Skip this project if there's already a project registered with exactly the same path

src/features/envCommands.ts

@@ -369,8 +369,29 @@ export async function addPythonProjectCommand(
             name: resource.fsPath,
             rootUri: resource,
         };
+
+        // When a URI is provided (right-click in explorer), directly use the existingProjects creator
+        const existingProjectsCreator = pc.getProjectCreators().find((c) => c.name === 'existingProjects');
+        if (existingProjectsCreator) {
+            try {
+                if (existingProjectsCreator.supportsQuickCreate) {
+                    options = {
+                        ...options,
+                        quickCreate: true,
+                    };
+                }
+                await existingProjectsCreator.create(options);
+                return;
+            } catch (ex) {
+                if (ex === QuickInputButtons.Back) {
+                    return addPythonProjectCommand(resource, wm, em, pc);
+                }
+                throw ex;
+            }
+        }
     }
 
+    // If not a URI or existingProjectsCreator not found, fall back to picker
     const creator: PythonProjectCreator | undefined = await pickCreator(pc.getProjectCreators());
     if (!creator) {
         return;