[ DDS ] Add errorCode to DartDevelopmentServiceException to better

communicate reason for error

Change-Id: I5041558ad6370f873dc23515fdad1ec8a2cf4ba8
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/172880
Reviewed-by: Jonah Williams <jonahwilliams@google.com>
Commit-Queue: Ben Konyi <bkonyi@google.com>

pkg/dds/CHANGELOG.md

@@ -1,3 +1,7 @@
+# 1.6.0
+- Added `errorCode` to `DartDevelopmentServiceException` to communicate the
+  underlying reason of the failure.
+
 # 1.5.1
 - Improve internal error handling for situations with less than graceful
   shutdowns.

pkg/dds/lib/dds.dart

@@ -159,9 +159,36 @@ abstract class DartDevelopmentService {
 }
 
 class DartDevelopmentServiceException implements Exception {
-  DartDevelopmentServiceException._(this.message);
+  /// Set when `DartDeveloperService.startDartDevelopmentService` is called and
+  /// the target VM service already has a Dart Developer Service instance
+  /// connected.
+  static const int existingDdsInstanceError = 1;
+
+  /// Set when the connection to the remote VM service terminates unexpectedly
+  /// during Dart Development Service startup.
+  static const int failedToStartError = 2;
+
+  /// Set when a connection error has occurred after startup.
+  static const int connectionError = 3;
+
+  factory DartDevelopmentServiceException._existingDdsInstanceError(
+      String message) {
+    return DartDevelopmentServiceException._(existingDdsInstanceError, message);
+  }
+
+  factory DartDevelopmentServiceException._failedToStartError() {
+    return DartDevelopmentServiceException._(
+        failedToStartError, 'Failed to start Dart Development Service');
+  }
+
+  factory DartDevelopmentServiceException._connectionError(String message) {
+    return DartDevelopmentServiceException._(connectionError, message);
+  }
+
+  DartDevelopmentServiceException._(this.errorCode, this.message);
 
   String toString() => 'DartDevelopmentServiceException: $message';
 
+  final int errorCode;
   final String message;
 }

pkg/dds/lib/src/dds_impl.dart

@@ -49,17 +49,14 @@ class _DartDevelopmentService implements DartDevelopmentService {
           shutdown();
           if (!started && !completer.isCompleted) {
             completer.completeError(
-              DartDevelopmentServiceException._(
-                'Failed to start Dart Development Service',
-              ),
-            );
+                DartDevelopmentServiceException._failedToStartError());
           }
         },
         onError: (e, st) {
           shutdown();
           if (!completer.isCompleted) {
             completer.completeError(
-              DartDevelopmentServiceException._(e.toString()),
+              DartDevelopmentServiceException._connectionError(e.toString()),
               st,
             );
           }
@@ -118,7 +115,7 @@ class _DartDevelopmentService implements DartDevelopmentService {
     } on json_rpc.RpcException catch (e) {
       await _server.close(force: true);
       // _yieldControlToDDS fails if DDS is not the only VM service client.
-      throw DartDevelopmentServiceException._(
+      throw DartDevelopmentServiceException._existingDdsInstanceError(
         e.data != null ? e.data['details'] : e.toString(),
       );
     }

pkg/dds/pubspec.yaml

@@ -3,7 +3,7 @@ description: >-
   A library used to spawn the Dart Developer Service, used to communicate with
   a Dart VM Service instance.
 
-version: 1.5.1
+version: 1.6.0
 
 homepage: https://github.com/dart-lang/sdk/tree/master/pkg/dds
 

pkg/dds/test/handles_connection_closed_before_full_header.dart

@@ -30,6 +30,7 @@ void main() async {
       await DartDevelopmentService.startDartDevelopmentService(uri);
       fail('Unexpected successful connection.');
     } on DartDevelopmentServiceException catch (e) {
+      expect(e.errorCode, DartDevelopmentServiceException.connectionError);
       expect(e.toString().contains('WebSocketChannelException'), true);
     }
   });

pkg/dds/test/smoke_test.dart

@@ -107,6 +107,8 @@ void main() {
       } on DartDevelopmentServiceException catch (e) {
         expect(e.message,
             'Existing VM service clients prevent DDS from taking control.');
+        expect(e.errorCode,
+            DartDevelopmentServiceException.existingDdsInstanceError);
       }
     });
   });