Handle missing final discovery snapshot

Avoid bounded retries when the cache remains definitively empty.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 6b12d843-8011-4bfc-9ba9-f75761eadee2

Author: StellaHuang95

src/managers/builtin/inlineScript/envManager.ts

@@ -498,17 +498,24 @@ export class InlineScriptEnvManager implements EnvironmentManager, Disposable {
         }
 
         if (checkForSnapshotChanges) {
+            let finalEntryNames: string[] | undefined;
             try {
-                const finalEntryNames = await fs.readdir(cacheRoot.fsPath);
+                finalEntryNames = await fs.readdir(cacheRoot.fsPath);
+            } catch (error) {
+                if (this.isDefinitivelyStalePathError(error)) {
+                    finalEntryNames = [];
+                } else {
+                    shouldRetry = true;
+                }
+            }
+            if (finalEntryNames !== undefined) {
                 const initialEntries = new Set(entryNames);
                 if (
                     finalEntryNames.length !== entryNames.length ||
                     finalEntryNames.some((entryName) => !initialEntries.has(entryName))
                 ) {
                     shouldRetry = true;
                 }
-            } catch {
-                shouldRetry = true;
             }
         }
 

src/test/managers/builtin/inlineScript/envManager.unit.test.ts

@@ -1588,6 +1588,23 @@ suite('InlineScriptEnvManager', () => {
             assert.deepStrictEqual(await manager.getEnvironments('all'), [environment]);
         });
 
+        test('does not retry when the final cache-root snapshot is definitively absent and empty', async () => {
+            const readdirStub = sinon.stub(fsExtra, 'readdir');
+            readdirStub.onFirstCall().resolves([]);
+            readdirStub.onSecondCall().rejects(Object.assign(new Error('cache root removed'), { code: 'ENOENT' }));
+            const retryManager = manager as unknown as {
+                getDiscoveryRetryDelayMs(attempt: number): number | undefined;
+            };
+            sinon.stub(retryManager, 'getDiscoveryRetryDelayMs').returns(0);
+
+            manager.startActivationDiscovery();
+            await waitForStubCallCount(readdirStub, 2);
+            await new Promise((resolve) => setTimeout(resolve, 25));
+
+            assert.strictEqual(readdirStub.callCount, 2);
+            assert.deepStrictEqual(await manager.getEnvironments('all'), []);
+        });
+
         test('refresh skips missing, invalid, unavailable, and non-directory cache entries', async () => {
             const valid = await createOwnedEnvironment();
             const cacheRoot = cacheLayout.getScriptEnvCacheRoot(globalStorageUri).fsPath;