V3 Streaming API throws UnimplementedError when you use SELECT pg_notify instead of NOTIFY on a specific channel

[bettdouglas]

I was reading the docs on https://www.postgresql.org/docs/current/sql-notify.html.

I'm glad that this library listens well to NOTIFY channel_name 'Payload' notifications.
It however fails on SELECT pg_notify('VIRTUAL','Payload 2');

import 'package:postgres/postgres_v3_experimental.dart';
import 'package:test/test.dart';
import 'package:dotenv/dotenv.dart';

void main() {
  late PgConnection connection;

  setUpAll(() async {
  final endpoint = PgEndpoint(host: 'localhost', database: 'postgres'); 
    connection = await PgConnection.open(endpoint);
  });

    test('can listen to virtual channel', () async {
    await connection.execute('LISTEN VIRTUAL;');
    final channel = connection.channels['virtual'].asBroadcastStream();
    channel.listen((event) {
      print(event);
    });
    print(channel);
    var count = 1;
    channel.listen(
      expectAsync1(
        (event) {
          if (count == 1) {
            expect(event, equals('Payload'));
          } else if (count == 2) {
            expect(event, equals('Payload 2'));
          }
          count++;
        },
        count: 2,
      ),
    );
    final result = await connection.execute(
      PgSql('''NOTIFY VIRTUAL, 'Payload';'''),
    );

    ///UnimplementedError: Text decoding for PgDataType.byteArray
    /// PostgresTextDecoder.convert
    /// text_codec.dart:247
    /// dart:convert                                    Codec.decode
    await connection.execute(
      // PgSql('''NOTIFY VIRTUAL, 'Payload 2';'''),
      PgSql('''SELECT pg_notify('VIRTUAL','Payload 2');'''),
    );
    print(result);
  });
}

This prints

Payload
UnimplementedError: Text decoding for PgDataType.byteArray
PostgresTextDecoder.convert
text_codec.dart:247
dart:convert                                    Codec.decode
_PgResultStreamSubscription.handleMessage
connection.dart:453
PgConnectionImplementation._handleMessage
connection.dart:220

How does one convert from byteArray to say a String that was the message sent by pg_notify?

@simolus3 any pointers?. Thanks in advance.

[simolus3]

Fixed by the linked PR which also contains a description of what's going wrong. You can use this workaround to fix the notify function invocation until then:

postgresql-dart/lib/src/v3/connection.dart

Lines 633 to 644 in 001d9bf

	@override
	Future<void> notify(String channel, [String? payload]) async {
	final statementCompleter = _notifyStatement ??= Completer()
	..complete(Future(() async {
	return _connection.prepare(PgSql(r'SELECT pg_notify($1, $2)',
	types: [PgDataType.text, PgDataType.text]));
	}));
	final statement = await statementCompleter.future;
	await statement.run([channel, payload]);
	}
	}

[bettdouglas]

Thanks a lot for fixing this @simolus3