Ensure Python environment defined in python.defaultInterpreterPath is returned via discovery API (#22389)

Closes #22268

Even when it is not the active interpreter for any workspace, it's still
a known environment which users could consider selecting.

Author: Kartik Raj

src/client/pythonEnvironments/base/locators/lowLevel/customVirtualEnvLocator.ts

@@ -92,8 +92,8 @@ export class CustomVirtualEnvironmentLocator extends FSWatchingLocator {
     }
 
     protected async initResources(): Promise<void> {
-        this.disposables.push(onDidChangePythonSetting(VENVPATH_SETTING_KEY, () => this.emitter.fire({})));
-        this.disposables.push(onDidChangePythonSetting(VENVFOLDERS_SETTING_KEY, () => this.emitter.fire({})));
+        this.disposables.push(onDidChangePythonSetting(VENVPATH_SETTING_KEY, () => this.fire()));
+        this.disposables.push(onDidChangePythonSetting(VENVFOLDERS_SETTING_KEY, () => this.fire()));
     }
 
     // eslint-disable-next-line class-methods-use-this

src/client/pythonEnvironments/base/locators/lowLevel/customWorkspaceLocator.ts

@@ -0,0 +1,47 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+import { PythonEnvKind } from '../../info';
+import { BasicEnvInfo, IPythonEnvsIterator } from '../../locator';
+import { FSWatchingLocator } from './fsWatchingLocator';
+import { getPythonSetting, onDidChangePythonSetting } from '../../../common/externalDependencies';
+import '../../../../common/extensions';
+import { traceVerbose } from '../../../../logging';
+import { DEFAULT_INTERPRETER_SETTING } from '../../../../common/constants';
+
+export const DEFAULT_INTERPRETER_PATH_SETTING_KEY = 'defaultInterpreterPath';
+
+/**
+ * Finds and resolves custom virtual environments that users have provided.
+ */
+export class CustomWorkspaceLocator extends FSWatchingLocator {
+    public readonly providerId: string = 'custom-workspace-locator';
+
+    constructor(private readonly root: string) {
+        super(
+            () => [],
+            async () => PythonEnvKind.Unknown,
+        );
+    }
+
+    protected async initResources(): Promise<void> {
+        this.disposables.push(
+            onDidChangePythonSetting(DEFAULT_INTERPRETER_PATH_SETTING_KEY, () => this.fire(), this.root),
+        );
+    }
+
+    // eslint-disable-next-line class-methods-use-this
+    protected doIterEnvs(): IPythonEnvsIterator<BasicEnvInfo> {
+        const iterator = async function* (root: string) {
+            traceVerbose('Searching for custom workspace envs');
+            const filename = getPythonSetting<string>(DEFAULT_INTERPRETER_PATH_SETTING_KEY, root);
+            if (!filename || filename === DEFAULT_INTERPRETER_SETTING) {
+                // If the user has not set a custom interpreter, our job is done.
+                return;
+            }
+            yield { kind: PythonEnvKind.Unknown, executablePath: filename };
+            traceVerbose(`Finished searching for custom workspace envs`);
+        };
+        return iterator(this.root);
+    }
+}

src/client/pythonEnvironments/base/locators/lowLevel/fsWatchingLocator.ts

@@ -128,6 +128,10 @@ export abstract class FSWatchingLocator extends LazyResourceBasedLocator {
         watchableRoots.forEach((root) => this.startWatchers(root));
     }
 
+    protected fire(args = {}): void {
+        this.emitter.fire({ ...args, providerId: this.providerId });
+    }
+
     private startWatchers(root: string): void {
         const opts = this.creationOptions;
         if (isWatchingAFile(opts)) {

src/client/pythonEnvironments/common/externalDependencies.ts

@@ -175,8 +175,9 @@ export async function* getSubDirs(
  * Returns the value for setting `python.<name>`.
  * @param name The name of the setting.
  */
-export function getPythonSetting<T>(name: string): T | undefined {
-    const settings = internalServiceContainer.get<IConfigurationService>(IConfigurationService).getSettings();
+export function getPythonSetting<T>(name: string, root?: string): T | undefined {
+    const resource = root ? vscode.Uri.file(root) : undefined;
+    const settings = internalServiceContainer.get<IConfigurationService>(IConfigurationService).getSettings(resource);
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
     return (settings as any)[name];
 }
@@ -186,9 +187,10 @@ export function getPythonSetting<T>(name: string): T | undefined {
  * @param name The name of the setting.
  * @param callback The listener function to be called when the setting changes.
  */
-export function onDidChangePythonSetting(name: string, callback: () => void): IDisposable {
+export function onDidChangePythonSetting(name: string, callback: () => void, root?: string): IDisposable {
     return vscode.workspace.onDidChangeConfiguration((event: vscode.ConfigurationChangeEvent) => {
-        if (event.affectsConfiguration(`python.${name}`)) {
+        const scope = root ? vscode.Uri.file(root) : undefined;
+        if (event.affectsConfiguration(`python.${name}`, scope)) {
             callback();
         }
     });

src/client/pythonEnvironments/index.ts

@@ -37,6 +37,7 @@ import { EnvsCollectionService } from './base/locators/composite/envsCollectionS
 import { IDisposable } from '../common/types';
 import { traceError } from '../logging';
 import { ActiveStateLocator } from './base/locators/lowLevel/activeStateLocator';
+import { CustomWorkspaceLocator } from './base/locators/lowLevel/customWorkspaceLocator';
 
 /**
  * Set up the Python environments component (during extension activation).'
@@ -182,7 +183,11 @@ function watchRoots(args: WatchRootsArgs): IDisposable {
 
 function createWorkspaceLocator(ext: ExtensionState): WorkspaceLocators {
     const locators = new WorkspaceLocators(watchRoots, [
-        (root: vscode.Uri) => [new WorkspaceVirtualEnvironmentLocator(root.fsPath), new PoetryLocator(root.fsPath)],
+        (root: vscode.Uri) => [
+            new WorkspaceVirtualEnvironmentLocator(root.fsPath),
+            new PoetryLocator(root.fsPath),
+            new CustomWorkspaceLocator(root.fsPath),
+        ],
         // Add an ILocator factory func here for each kind of workspace-rooted locator.
     ]);
     ext.disposables.push(locators);

src/test/pythonEnvironments/base/locators/lowLevel/customVirtualEnvLocator.unit.test.ts

@@ -213,7 +213,7 @@ suite('CustomVirtualEnvironment Locator', () => {
 
     test('onChanged fires if venvPath setting changes', async () => {
         const events: PythonEnvsChangedEvent[] = [];
-        const expected: PythonEnvsChangedEvent[] = [{}];
+        const expected: PythonEnvsChangedEvent[] = [{ providerId: locator.providerId }];
         locator.onChanged((e) => events.push(e));
 
         await getEnvs(locator.iterEnvs());
@@ -228,7 +228,7 @@ suite('CustomVirtualEnvironment Locator', () => {
 
     test('onChanged fires if venvFolders setting changes', async () => {
         const events: PythonEnvsChangedEvent[] = [];
-        const expected: PythonEnvsChangedEvent[] = [{}];
+        const expected: PythonEnvsChangedEvent[] = [{ providerId: locator.providerId }];
         locator.onChanged((e) => events.push(e));
 
         await getEnvs(locator.iterEnvs());