Add notification when re-selecting the same workspace environment (#441)

fixes microsoft/vscode-python-environments#58

## Problem

When a user selects "Set As Workspace Environment" for an environment
that's already selected as the workspace environment, there's no
feedback provided to the user. This can be confusing, as it appears that
nothing happens when clicking the button.

## Solution

This PR adds feedback to users when they attempt to select an
environment that's already set as the workspace environment:

1. When a user has one folder/project open and tries to set the same
environment that's already selected
2. The user will now see an information message: "This environment is
already selected for the workspace." but its more verbose

Fixes #58 and refined by @eleanorjboyd

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: eleanorjboyd <26030610+eleanorjboyd@users.noreply.github.com>

Author: Copilot

src/features/envCommands.ts

@@ -3,6 +3,7 @@ import {
     CreateEnvironmentOptions,
     PythonEnvironment,
     PythonEnvironmentApi,
+    PythonProject,
     PythonProjectCreator,
     PythonProjectCreatorOptions,
 } from '../api';
@@ -21,7 +22,7 @@ import {} from '../common/errors/utils';
 import { pickEnvironment } from '../common/pickers/environments';
 import { pickCreator, pickEnvironmentManager, pickPackageManager } from '../common/pickers/managers';
 import { pickProject, pickProjectMany } from '../common/pickers/projects';
-import { activeTextEditor, showErrorMessage } from '../common/window.apis';
+import { activeTextEditor, showErrorMessage, showInformationMessage } from '../common/window.apis';
 import { quoteArgs } from './execution/execUtils';
 import { runAsTask } from './execution/runAsTask';
 import { runInTerminal } from './terminal/runInTerminal';
@@ -212,8 +213,8 @@ export async function setEnvironmentCommand(
             if (projects.length > 0) {
                 const selected = await pickProjectMany(projects);
                 if (selected && selected.length > 0) {
-                    const uris = selected.map((p) => p.uri);
-                    await em.setEnvironments(uris, view.environment);
+                    // Check if the selected environment is already the current one for each project
+                    await setEnvironmentForProjects(selected, context.environment, em);
                 }
             } else {
                 await em.setEnvironments('global', view.environment);
@@ -271,13 +272,47 @@ export async function setEnvironmentCommand(
         });
 
         if (selected) {
-            await em.setEnvironments(uris, selected);
+            // Use the same logic for checking already set environments
+            await setEnvironmentForProjects(projects, selected, em);
         }
     } else {
         traceError(`Invalid context for setting environment command: ${context}`);
         showErrorMessage('Invalid context for setting environment');
     }
 }
+/**
+ * Sets the environment for the given projects, showing a warning for those already set.
+ * @param selectedProjects Array of  PythonProject selected by user
+ * @param environment The environment to set for the projects
+ * @param em The EnvironmentManagers instance
+ */
+async function setEnvironmentForProjects(
+    selectedProjects: PythonProject[],
+    environment: PythonEnvironment,
+    em: EnvironmentManagers,
+) {
+    let alreadySet: PythonProject[] = [];
+    for (const p of selectedProjects) {
+        const currentEnv = await em.getEnvironment(p.uri);
+        if (currentEnv?.envId.id === environment.envId.id) {
+            alreadySet.push(p);
+        }
+    }
+    if (alreadySet.length > 0) {
+        const env = alreadySet.length > 1 ? 'environments' : 'environment';
+        showInformationMessage(
+            `"${environment.name}" is already selected as the ${env} for: ${alreadySet
+                .map((p) => `"${p.name}"`)
+                .join(', ')}`,
+        );
+    }
+    const toSet: PythonProject[] = selectedProjects.filter((p) => !alreadySet.includes(p));
+    const uris = toSet.map((p) => p.uri);
+    if (uris.length === 0) {
+        return;
+    }
+    await em.setEnvironments(uris, environment);
+}
 
 export async function resetEnvironmentCommand(
     context: unknown,