Server notification to indicate `pub list-dir` fallback.

pkg/analysis_server/lib/src/context_manager.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library context.directory.manager;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:convert';
 import 'dart:core' hide Resource;
@@ skipping 820 matching lines @@
         if (pathContext.basename(packagespecFile.path) == PACKAGE_SPEC_NAME) {
           Packages packages = _readPackagespec(packagespecFile);
           return new PackagesFileDisposition(packages);
         }
         if (packageResolverProvider != null) {
           UriResolver resolver = packageResolverProvider(folder);
           if (resolver != null) {
             return new CustomPackageResolverDisposition(resolver);
           }
         }
+
+        // Notify server that no `.packages` file was found (and there is no
+        // alternative resolver provider).
+        AnalysisEngine.instance.logger.logError(
+            'No `.packages` for $folder, falling back to `pub`.');
+
         ServerPerformanceStatistics.pub.makeCurrentWhile(() {
           packageMapInfo = _packageMapProvider.computePackageMap(folder);
         });
       } finally {
         callbacks.endComputePackageMap();
       }
       for (String dependencyPath in packageMapInfo.dependencies) {
         addDependency(dependencyPath);
       }
       if (packageMapInfo.packageMap == null) {
@@ skipping 603 matching lines @@
           var path = resourceProvider.pathContext.fromUri(uri);
           packageMap[name] = <Folder>[resourceProvider.getFolder(path)];
         }
       });
       return <UriResolver>[new SdkExtUriResolver(packageMap)];
     } else {
       return const <UriResolver>[];
     }
   }
 }