Fix: do not close connection after an empty statement (#403)

Author: isoos

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## 3.4.6
+
+- Fix: do not close connection after an empty statement.
+
 ## 3.4.5
 
 - `close(force: true)` to indicate intent to force-close pending queries and resources. [#396](https://github.com/isoos/postgresql-dart/pull/396) by [davidmartos96](https://github.com/davidmartos96)

lib/src/message_window.dart

@@ -21,6 +21,7 @@ Map<int, _ServerMessageFn> _messageTypeMap = {
   67: (r, _) => CommandCompleteMessage.parse(r),
   68: (r, _) => DataRowMessage.parse(r),
   69: ErrorResponseMessage.parse,
+  73: (_, __) => EmptyQueryResponseMessage(),
   75: (r, _) => BackendKeyMessage.parse(r),
   82: AuthenticationMessage.parse,
   83: (r, l) => ParameterStatusMessage.parse(r),

lib/src/messages/server_messages.dart

@@ -449,6 +449,13 @@ Future<XLogDataMessage> parseXLogDataMessage(
   }
 }
 
+class EmptyQueryResponseMessage extends ServerMessage {
+  EmptyQueryResponseMessage();
+
+  @override
+  String toString() => 'EmptyQueryResponseMessage()';
+}
+
 class UnknownMessage extends ServerMessage {
   final int code;
   final Uint8List bytes;
@@ -476,6 +483,9 @@ class UnknownMessage extends ServerMessage {
     }
     return true;
   }
+
+  @override
+  String toString() => 'UnknownMessage($code, length=${bytes.length})';
 }
 
 abstract class ErrorFieldId {

lib/src/v3/connection.dart

@@ -926,6 +926,8 @@ class _PgResultStreamSubscription
         // TODO(osaxma): Prevent executing queries when Streaming Replication
         //               is ongoing
         await _completeQuery();
+      case EmptyQueryResponseMessage():
+        break;
       default:
         // Unexpected message - either a severe bug in this package or in the
         // connection. We better close it.

pubspec.yaml

@@ -1,6 +1,6 @@
 name: postgres
 description: PostgreSQL database driver. Supports statement reuse and binary protocol and connection pooling.
-version: 3.4.5
+version: 3.4.6
 homepage: https://github.com/isoos/postgresql-dart
 topics:
   - sql

test/pool_test.dart

@@ -135,9 +135,10 @@ void main() {
         ),
       );
 
-      // this doesn't throw but it causes the connection to close
       await db.execute('-- test');
-      await db.execute('SELECT 1');
+      expect(await db.execute('SELECT 1'), [
+        [1]
+      ]);
     });
   });
 

test/v3_close_test.dart

@@ -71,6 +71,13 @@ void main() {
       await conn2.execute(
           'select pg_terminate_backend($conn1PID) from pg_stat_activity;');
     });
+
+    test('empty query does not close connection', () async {
+      await conn1.execute('-- test');
+      expect(await conn1.execute('SELECT 1'), [
+        [1]
+      ]);
+    });
   });
 
   group('force close', () {