fix(data-connection-layer): resolve DataConnectionLayer-014..017 — real logger for OPC UA client, initial-connect failover, accurate subscribe response, per-tag write-batch results

src/ScadaLink.DataConnectionLayer/Adapters/OpcUaDataConnection.cs

@@ -228,10 +228,28 @@ public class OpcUaDataConnection : IDataConnection
 
     public async Task<IReadOnlyDictionary<string, WriteResult>> WriteBatchAsync(IDictionary<string, object?> values, CancellationToken cancellationToken = default)
     {
+        // DataConnectionLayer-017: a mid-batch fault must not abort the whole batch.
+        // WriteAsync calls EnsureConnected(), which throws InvalidOperationException when
+        // the connection drops partway through; catch per-tag exceptions and record a
+        // failed WriteResult so the caller (including WriteBatchAndWaitAsync) receives a
+        // complete result map. OperationCanceledException is still propagated so a
+        // cancelled batch aborts as a whole — mirrors the DCL-007 fix for ReadBatchAsync.
         var results = new Dictionary<string, WriteResult>();
         foreach (var (tagPath, value) in values)
         {
-            results[tagPath] = await WriteAsync(tagPath, value, cancellationToken);
+            try
+            {
+                results[tagPath] = await WriteAsync(tagPath, value, cancellationToken);
+            }
+            catch (OperationCanceledException)
+            {
+                // Cancellation aborts the whole batch — propagate it.
+                throw;
+            }
+            catch (Exception ex)
+            {
+                results[tagPath] = new WriteResult(false, ex.Message);
+            }
         }
         return results;
     }

src/ScadaLink.DataConnectionLayer/Adapters/RealOpcUaClient.cs

@@ -316,11 +316,24 @@ public class RealOpcUaClientFactory : IOpcUaClientFactory
 {
     private readonly OpcUaGlobalOptions _globalOptions;
 
+    // DataConnectionLayer-014: a real logger must be threaded through to every
+    // RealOpcUaClient this factory builds, otherwise the DCL-012 auto-accept-certificate
+    // warning emitted in RealOpcUaClient.ConnectAsync sinks into NullLogger and is never
+    // seen in production. The factory is constructed by DataConnectionFactory, which has
+    // an ILoggerFactory available.
+    private readonly ILoggerFactory _loggerFactory;
+
     public RealOpcUaClientFactory() : this(new OpcUaGlobalOptions()) { }
+
     public RealOpcUaClientFactory(OpcUaGlobalOptions globalOptions)
+        : this(globalOptions, NullLoggerFactory.Instance) { }
+
+    public RealOpcUaClientFactory(OpcUaGlobalOptions globalOptions, ILoggerFactory loggerFactory)
     {
         _globalOptions = globalOptions;
+        _loggerFactory = loggerFactory;
     }
 
-    public IOpcUaClient Create() => new RealOpcUaClient(_globalOptions);
+    public IOpcUaClient Create() =>
+        new RealOpcUaClient(_globalOptions, _loggerFactory.CreateLogger<RealOpcUaClient>());
 }