[analysis_server] Don't rebuild contexts on deletion of an analysis root

This is a partial revert of ca95230 (it removes the behaviour change and the test that verifies this, but leaves two additional tests that were added relating to roots that are created later).

If we rebuild contexts when a root is deleted, we may get stuck in a loop because we will again try to recreate the same (deleted) root, and then the watcher will close in a way that looks like a deleted folder, and we will repeat.

Fixes #60863

Change-Id: I10289160b341d273e8e409184a1c013c7fb9439d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/433140
Reviewed-by: Konstantin Shcheglov <[email protected]>
Commit-Queue: Brian Wilkerson <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>

Author: DanTup

pkg/analysis_server/lib/src/context_manager.dart

@@ -227,7 +227,7 @@ class ContextManagerImpl implements ContextManager {
       HashMap<Folder, AnalysisDriver>();
 
   /// Subscriptions to watch included resources for changes.
-  final Set<StreamSubscription<WatchEvent>> watcherSubscriptions = {};
+  final List<StreamSubscription<WatchEvent>> watcherSubscriptions = [];
 
   /// Whether or not the watchers have been paused.
   ///
@@ -623,24 +623,12 @@ class ContextManagerImpl implements ContextManager {
           for (var included in analysisContext.contextRoot.included) {
             var watcher = included.watch();
             watchers.add(watcher);
-            var watcherSubscription = watcher.changes.listen(
-              _scheduleWatchEvent,
-              onError: _handleWatchInterruption,
+            watcherSubscriptions.add(
+              watcher.changes.listen(
+                _scheduleWatchEvent,
+                onError: _handleWatchInterruption,
+              ),
             );
-            watcherSubscriptions.add(watcherSubscription);
-            // When a directory is deleted, the watcher will be closed. Detect
-            // this by checking whether the watcher is still active in
-            // `changeSubscriptions` (it will first be removed if we are
-            // closing the watcher ourselves).
-            watcherSubscription.onDone(() {
-              if (watcherSubscriptions.contains(watcherSubscription)) {
-                _instrumentationService.logInfo(
-                  'Watcher for $rootFolder unexpectedly closed. '
-                  'Assuming root was deleted, rebuilding...',
-                );
-                refresh();
-              }
-            });
           }
 
           _watchBlazeFilesIfNeeded(rootFolder, driver);
@@ -778,14 +766,10 @@ class ContextManagerImpl implements ContextManager {
   }
 
   Future<void> _destroyAnalysisContexts() async {
-    // Clear `watcherSubscriptions` before cancelling each subscription
-    // because the presences of a watcher in `watcherSubscriptions` is used
-    // to know if the watcher closed prematurely.
-    var subscriptionsToCancel = watcherSubscriptions.toSet();
+    for (var subscription in watcherSubscriptions) {
+      await subscription.cancel();
+    }
     watcherSubscriptions.clear();
-    await Future.wait(
-      subscriptionsToCancel.map((subscription) => subscription.cancel()),
-    );
 
     var collection = _collection;
     _collection = null;

pkg/analysis_server/test/integration/analysis/error_test.dart

@@ -18,38 +18,7 @@ void main() {
 @reflectiveTest
 class AnalysisErrorIntegrationTest
     extends AbstractAnalysisServerIntegrationTest {
-  Future<void> test_analysisRootDeleted_rebuildsContexts() async {
-    // To simplify testing, use two analysis roots. When we delete one of them
-    // we can use the notification of diagnostics sent for the other as
-    // validation that contexts were rebuilt.
-    var rootToKeepPath = sourcePath('packageKeep');
-    var filetoKeepPath = sourcePath('packageKeep/lib/test.dart');
-    var rootToDeletePath = sourcePath('packageDelete');
-    var fileToDeletePath = sourcePath('packageDelete/lib/test.dart');
-    var content = 'invalidCode';
-
-    // Create the folders/files up-front.
-    writeFile(filetoKeepPath, content);
-    writeFile(fileToDeletePath, content);
-
-    await sendServerSetSubscriptions([ServerService.STATUS]);
-    await sendAnalysisSetAnalysisRoots([rootToKeepPath, rootToDeletePath], []);
-    await analysisFinished;
-
-    // Start listening for the kept root being re-analyzed as a signal that
-    // the rebuild has completed.
-    var keptFileDiagnostics = onAnalysisErrors.firstWhere(
-      (params) => params.file == filetoKeepPath,
-    );
-
-    // Delete the folder which should trigger a rebuild.
-    deleteFolder(rootToDeletePath);
-
-    // Ensure this completes.
-    await keptFileDiagnostics;
-  }
-
-  Future<void> test_analysisRootDoesNotExist_addOverlay() async {
+  Future<void> test_analysisRootDoesNotExist() async {
     var packagePath = sourcePath('package');
     var filePath = sourcePath('package/lib/test.dart');
     var content = '''