Fix empty LocalizedText binary field encoding

src/Opc.Ua.Types/Encoders/BinaryEncoder.cs

@@ -806,12 +806,13 @@ public void WriteLocalizedText(string? fieldName, LocalizedText value)
             // calculate the encoding.
             byte encoding = 0;
 
-            if (value.Locale != null)
+            // Empty fields carry no information; omit them as required by OPC 10000-6, Table 24.
+            if (!string.IsNullOrEmpty(value.Locale))
             {
                 encoding |= (byte)LocalizedTextEncodingBits.Locale;
             }
 
-            if (value.Text != null)
+            if (!string.IsNullOrEmpty(value.Text))
             {
                 encoding |= (byte)LocalizedTextEncodingBits.Text;
             }

tests/Opc.Ua.Aot.Tests/VariantStorageAotTests.cs

@@ -154,7 +154,11 @@
                 int expectedOrder = value.Equals(Variant.Null) ? 0 : int.MinValue;
                 await Assert.That(value.CompareTo(value)).IsEqualTo(expectedOrder);
                 await Assert.That(value.GetHashCode()).IsEqualTo(input.GetHashCode());
-                await CheckAsync(input, value, default(VariantBuilder)).ConfigureAwait(false);
+                var binaryExpected = new LocalizedText(
+                    string.IsNullOrEmpty(input.Locale) ? null : input.Locale,
+                    string.IsNullOrEmpty(input.Text) ? null : input.Text);
+                await CheckAsync(input, value, default(VariantBuilder), binaryExpected)
+                    .ConfigureAwait(false);
             }
         }
 
@@ -189,7 +193,16 @@
             await Assert.That((Variant.From(0L) | Variant.From(7L)).GetInt64()).IsEqualTo(7L);
         }
 
-        private async Task CheckAsync<T>(T input, Variant value, IVariantBuilder<T> builder)
+        private Task CheckAsync<T>(T input, Variant value, IVariantBuilder<T> builder)
+        {
+            return CheckAsync(input, value, builder, input);
+        }
+
+        private async Task CheckAsync<T>(
+            T input,
+            Variant value,
+            IVariantBuilder<T> builder,
+            T binaryExpected)
         {
             await Assert.That(EqualityComparer<T>.Default.Equals(builder.GetValue(value), input)).IsTrue();
             await Assert.That(builder.WithValue(input).Equals(value)).IsTrue();
@@ -204,7 +217,7 @@
                 encoder.CloseAndReturnBuffer() ?? throw new InvalidOperationException("No encoded value."), context);
             Variant decoded = decoder.ReadVariant(null);
             await Assert.That(decoded.TypeInfo).IsEqualTo(value.TypeInfo);
-            await Assert.That(decoded.Equals(value)).IsTrue();
+            await Assert.That(decoded.Equals(Variant.From(binaryExpected))).IsTrue();
         }
 
         private sealed class NativeMemoryManager : MemoryManager<byte>

tests/Opc.Ua.Types.Tests/BuiltIn/LocalizedTextTests.cs

@@ -1,5 +1,6 @@
 using System.Collections.Generic;
 using NUnit.Framework;
+using Opc.Ua.Tests;
 
 namespace Opc.Ua.Types.Tests.BuiltIn
 {
@@ -249,5 +250,54 @@ public void LocalizedText_MulLocale_DeepCopy()
                 Is.EqualTo(localizedText.Translations["fr-FR"]),
                 "French translation should be the same");
         }
+
+        [TestCase(null, null, 0x00)]
+        [TestCase("", "", 0x00)]
+        [TestCase("en-US", null, 0x01)]
+        [TestCase("en-US", "", 0x01)]
+        [TestCase(null, "Text", 0x02)]
+        [TestCase("", "Text", 0x02)]
+        [TestCase("en-US", "Text", 0x03)]
+        public void BinaryEncodingOmitsNullOrEmptyFields(
+            string? locale,
+            string? text,
+            byte expectedEncodingMask)
+        {
+            ITelemetryContext telemetryContext = NUnitTelemetryContext.Create();
+            var messageContext = ServiceMessageContext.CreateEmpty(telemetryContext);
+            byte[] buffer;
+            using (var encoder = new BinaryEncoder(messageContext))
+            {
+                encoder.WriteLocalizedText(null, new LocalizedText(locale, text));
+                buffer = encoder.CloseAndReturnBuffer() ??
+                    throw new AssertionException("The encoder returned no buffer.");
+            }
+
+            Assert.That(buffer[0], Is.EqualTo(expectedEncodingMask));
+            using var decoder = new BinaryDecoder(buffer, messageContext);
+            LocalizedText decoded = decoder.ReadLocalizedText(null);
+            Assert.That(decoded.Locale, Is.EqualTo(string.IsNullOrEmpty(locale) ? null : locale));
+            Assert.That(decoded.Text, Is.EqualTo(string.IsNullOrEmpty(text) ? null : text));
+        }
+
+        [Test]
+        public void TranslationBackedEmptyLocaleIsNotEncodedInBinary()
+        {
+            ITelemetryContext telemetryContext = NUnitTelemetryContext.Create();
+            var messageContext = ServiceMessageContext.CreateEmpty(telemetryContext);
+            byte[] buffer;
+            using (var encoder = new BinaryEncoder(messageContext))
+            {
+                encoder.WriteLocalizedText(null, new LocalizedText("Key", string.Empty, "Text"));
+                buffer = encoder.CloseAndReturnBuffer() ??
+                    throw new AssertionException("The encoder returned no buffer.");
+            }
+
+            Assert.That(buffer[0], Is.EqualTo(0x02));
+            using var decoder = new BinaryDecoder(buffer, messageContext);
+            LocalizedText decoded = decoder.ReadLocalizedText(null);
+            Assert.That(decoded.Locale, Is.Null);
+            Assert.That(decoded.Text, Is.EqualTo("Text"));
+        }
     }
 }