Add DisableableLocator.

Author: ericsnowcurrently

src/client/pythonEnvironments/base/locators.ts

@@ -3,8 +3,8 @@
 
 import { chain } from '../../common/utils/async';
 import { PythonEnvInfo } from './info';
-import { ILocator, PythonEnvsIterator, PythonLocatorQuery } from './locator';
-import { PythonEnvsWatchers } from './watchers';
+import { ILocator, NOOP_ITERATOR, PythonEnvsIterator, PythonLocatorQuery } from './locator';
+import { DisableableEnvsWatcher, PythonEnvsWatchers } from './watchers';
 
 /**
  * A wrapper around a set of locators.
@@ -24,3 +24,22 @@ export class Locators extends PythonEnvsWatchers {
         return chain<PythonEnvInfo>(iterators);
     }
 }
+
+/**
+ * A locator wrapper that can be disabled.
+ */
+export class DisableableLocator extends DisableableEnvsWatcher {
+    constructor(
+        // To wrapp more than one use `Locators`.
+        private readonly locator: ILocator
+    ) {
+        super(locator);
+    }
+
+    public iterEnvs(query?: PythonLocatorQuery): PythonEnvsIterator {
+        if (!this.isEnabled) {
+            return NOOP_ITERATOR;
+        }
+        return this.locator.iterEnvs(query);
+    }
+}