From a157ddbf94ee8905197da14f90aac6e1c17713fd Mon Sep 17 00:00:00 2001
From: Ben Konyi <bkonyi@google.com>
Date: Wed, 18 Nov 2020 23:45:41 +0000
Subject: [PATCH] [ 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                          |  4 +++
 pkg/dds/lib/dds.dart                          | 29 ++++++++++++++++++-
 pkg/dds/lib/src/dds_impl.dart                 |  9 ++----
 pkg/dds/pubspec.yaml                          |  2 +-
 ..._connection_closed_before_full_header.dart |  1 +
 pkg/dds/test/smoke_test.dart                  |  2 ++
 6 files changed, 39 insertions(+), 8 deletions(-)

diff --git a/pkg/dds/CHANGELOG.md b/pkg/dds/CHANGELOG.md
index 54979eb3453..953ac0bd40a 100644
--- a/pkg/dds/CHANGELOG.md
+++ b/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.
diff --git a/pkg/dds/lib/dds.dart b/pkg/dds/lib/dds.dart
index 0f716c68959..29cc2881984 100644
--- a/pkg/dds/lib/dds.dart
+++ b/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;
 }
diff --git a/pkg/dds/lib/src/dds_impl.dart b/pkg/dds/lib/src/dds_impl.dart
index fbb6bbab77d..ad0e46fc58c 100644
--- a/pkg/dds/lib/src/dds_impl.dart
+++ b/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(),
       );
     }
diff --git a/pkg/dds/pubspec.yaml b/pkg/dds/pubspec.yaml
index a04a63c5364..d4132a1cb0f 100644
--- a/pkg/dds/pubspec.yaml
+++ b/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
 
diff --git a/pkg/dds/test/handles_connection_closed_before_full_header.dart b/pkg/dds/test/handles_connection_closed_before_full_header.dart
index 65d643684fb..80f1744d7a5 100644
--- a/pkg/dds/test/handles_connection_closed_before_full_header.dart
+++ b/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);
     }
   });
diff --git a/pkg/dds/test/smoke_test.dart b/pkg/dds/test/smoke_test.dart
index 0a7347c274d..d3178936bc7 100644
--- a/pkg/dds/test/smoke_test.dart
+++ b/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);
       }
     });
   });