Remove items from array in reverse order (#18383)

* Remove items from array in reverse order

* Fix linter

* Update src/client/pythonEnvironments/base/locators/composite/envsCollectionCache.ts

Co-authored-by: Kartik Raj <karraj@microsoft.com>

* Update src/client/pythonEnvironments/base/locators/composite/envsCollectionCache.ts

Co-authored-by: Kartik Raj <karraj@microsoft.com>

Author: DonJayamanne

news/2 Fixes/18382.md

@@ -0,0 +1 @@
+Ensure items are removed from the array in reverse order when using array indices.

src/client/pythonEnvironments/base/locators/composite/envsCollectionCache.ts

@@ -84,7 +84,10 @@ export class PythonEnvInfoCache extends PythonEnvsWatcher<PythonEnvCollectionCha
          * exist.
          */
         const areEnvsValid = await Promise.all(this.envs.map((e) => pathExists(e.executable.filename)));
-        const invalidIndexes = areEnvsValid.map((isValid, index) => (isValid ? -1 : index)).filter((i) => i !== -1);
+        const invalidIndexes = areEnvsValid
+            .map((isValid, index) => (isValid ? -1 : index))
+            .filter((i) => i !== -1)
+            .reverse(); // Reversed so indexes do not change when deleting
         invalidIndexes.forEach((index) => {
             const env = this.envs.splice(index, 1)[0];
             this.fire({ old: env, new: undefined });