[analysis_server] Handle directory watcher closed on windows.

Change-Id: I11d1d9a324ebb27a920837ee4382b89e7cbb0253
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/125765
Reviewed-by: Konstantin Shcheglov <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Mike Fairhurst <[email protected]>

Author: MichaelRFairhurst

pkg/analysis_server/lib/src/context_manager.dart

@@ -786,8 +786,8 @@ class ContextManagerImpl implements ContextManager {
       bool isManaged = rootInfo._managesOrHasChildThatManages(includedPath);
       if (!isManaged) {
         ContextInfo parent = _getParentForNewContext(includedPath);
-        changeSubscriptions[includedFolder] =
-            includedFolder.changes.listen(_handleWatchEvent);
+        changeSubscriptions[includedFolder] = includedFolder.changes
+            .listen(_handleWatchEvent, onError: _handleWatchInterruption);
         _createContexts(parent, includedFolder, excludedPaths, false);
       }
     }
@@ -1407,6 +1407,15 @@ class ContextManagerImpl implements ContextManager {
     callbacks.afterWatchEvent(event);
   }
 
+  /// On windows, the directory watcher may overflow, and we must recover.
+  void _handleWatchInterruption(dynamic error, StackTrace stackTrace) {
+    // We've handled the error, so we only have to log it.
+    AnalysisEngine.instance.instrumentationService
+        .logError('Watcher error; refreshing contexts.\n$error\n$stackTrace');
+    // TODO(mfairhurst): Optimize this, or perhaps be less complete.
+    refresh(null);
+  }
+
   void _handleWatchEventImpl(WatchEvent event) {
     // Figure out which context this event applies to.
     // TODO(brianwilkerson) If a file is explicitly included in one context

pkg/analyzer/lib/file_system/physical_file_system.dart

@@ -262,7 +262,12 @@ class _PhysicalFolder extends _PhysicalResource implements Folder {
   @override
   Stream<WatchEvent> get changes =>
       new DirectoryWatcher(_entry.path).events.handleError((error) {},
-          test: (error) => error is io.FileSystemException);
+          test: (error) =>
+              error is io.FileSystemException &&
+              // Don't suppress "Directory watcher closed," so the outer
+              // listener can see the interruption & act on it.
+              !error.message
+                  .startsWith("Directory watcher closed unexpectedly"));
 
   /**
    * Return the underlying file being represented by this wrapper.