[Copilot]

opc-publisher could append a numeric suffix to a writer's DataSetWriterName (e.g. expected1 instead of expected) on outgoing telemetry despite no duplicate writers, and a container restart would change the emitted name — both surprising and non-deterministic.

Root cause

WriterGroupDataSource.UpdateAsync tracks live writer names in a local writerNames set used by CreateUniqueWriterName for deduplication. When a reconfiguration changes a writer's equality/hash (e.g. topic, QoS, TTL, publishing interval), the writer is removed and re-added. On removal the subscription was disposed and dropped from _writers, but its name was not removed from writerNames. The re-added writer then collided with its own stale name and got a suffix.

Since writerNames is rebuilt from live writers each update, the name oscillated with the parity of hash-changing reconfigurations — explaining both the intermittent suffix and why a restart (fresh StartAsync from an empty set) reset it.

Changes

• WriterGroupDataSource.UpdateAsync: release the writer's name from writerNames when removing it, so a re-added writer reuses the same name deterministically.

if (_writers.Remove(key, out var s))
{
    // Release the writer name so it can be reused by a
    // newly added writer below.
    writerNames.Remove(s.Name);
    await s.DisposeAsync().ConfigureAwait(false);
}

• WriterGroupDataSourceTests: added a regression test that reconfigures a single writer in a way that forces remove+add and asserts the emitted message WriterName stays expected (fails as expected1 without the fix).