Ensure that namespaces are always null or non-empty

src/AsmResolver.DotNet/TypeDefinition.cs

@@ -94,7 +94,8 @@ public TypeDefinition(Utf8String? ns, Utf8String? name, TypeAttributes attribute
         public Utf8String? Namespace
         {
             get => _namespace.GetValue(this);
-            set => _namespace.SetValue(value);
+            set => _namespace.SetValue(Utf8String.IsNullOrEmpty(value) ? null : value);
+            // According to the specification, the namespace should always be null or non-empty.
         }
 
         string? ITypeDescriptor.Namespace => Namespace;

src/AsmResolver.DotNet/TypeReference.cs

@@ -84,7 +84,8 @@ public Utf8String? Name
         public Utf8String? Namespace
         {
             get => _namespace.GetValue(this);
-            set => _namespace.SetValue(value);
+            set => _namespace.SetValue(Utf8String.IsNullOrEmpty(value) ? null : value);
+            // According to the specification, the namespace should always be null or non-empty.
         }
 
         string? ITypeDescriptor.Namespace => Namespace;

test/AsmResolver.DotNet.Tests/Signatures/SignatureComparerTest.cs

@@ -59,6 +59,14 @@ public void MatchTopLevelTypeRefTypeRefDifferentNamespace()
             Assert.NotEqual(reference1, reference2, _comparer);
         }
 
+        [Fact]
+        public void MatchTopLevelTypeRefTypeRefWithEmptyNamespace()
+        {
+            var reference1 = new TypeReference(_someAssemblyReference, null, "SomeType");
+            var reference2 = new TypeReference(_someAssemblyReference, "", "SomeType");
+            Assert.Equal(reference1, reference2, _comparer);
+        }
+
         [Fact]
         public void MatchTopLevelTypeRefTypeDef()
         {

test/AsmResolver.DotNet.Tests/TypeDefinitionTest.cs

@@ -773,5 +773,19 @@ public void AddSameNestedTypeToDifferentTypesShouldThrow()
             Assert.Throws<ArgumentException>(() => type2.NestedTypes.Add(nestedType));
         }
 
+        [Fact]
+        public void NamespaceShouldBeNullIfEmptyStringGiven()
+        {
+            var type = new TypeDefinition(string.Empty, "SomeType", TypeAttributes.Public);
+            Assert.Null(type.Namespace);
+        }
+
+        [Fact]
+        public void NamespaceShouldBeNullIfEmptyStringSet()
+        {
+            var type = new TypeDefinition("SomeNamespace", "SomeType", TypeAttributes.Public);
+            type.Namespace = string.Empty;
+            Assert.Null(type.Namespace);
+        }
     }
 }

test/AsmResolver.DotNet.Tests/TypeReferenceTest.cs

@@ -189,5 +189,22 @@ public void NonCorLibTypeToTypeSignatureShouldReturnTypeDefOrRef()
 
             Assert.Equal(signature.Type, reference, Comparer);
         }
+
+        [Fact]
+        public void NamespaceShouldBeNullIfEmptyStringGiven()
+        {
+            var module = new ModuleDefinition("SomeModule");
+            var type = new TypeReference(module, string.Empty, "SomeType");
+            Assert.Null(type.Namespace);
+        }
+
+        [Fact]
+        public void NamespaceShouldBeNullIfEmptyStringSet()
+        {
+            var module = new ModuleDefinition("SomeModule");
+            var type = new TypeReference(module, "SomeNamespace", "SomeType");
+            type.Namespace = string.Empty;
+            Assert.Null(type.Namespace);
+        }
     }
 }