change exception types and move check to its own method

Author: kyra-rk

src/MongoDB.Bson/Serialization/BsonSerializerRegistry.cs

@@ -93,7 +93,8 @@ public void RegisterSerializer(Type type, IBsonSerializer serializer)
             {
                 throw new ArgumentNullException("serializer");
             }
-            EnsureRegisteringASerializerForThisTypeIsAllowed(serializer, type);
+            EnsureRegisteringASerializerForThisTypeIsAllowed(type);
+            EnsureSerializerIsCompatibleWithType(serializer, type);
 
             if (!_cache.TryAdd(type, serializer))
             {
@@ -133,7 +134,8 @@ public bool TryRegisterSerializer(Type type, IBsonSerializer serializer)
             {
                 throw new ArgumentNullException(nameof(serializer));
             }
-            EnsureRegisteringASerializerForThisTypeIsAllowed(serializer, type);
+            EnsureRegisteringASerializerForThisTypeIsAllowed(type);
+            EnsureSerializerIsCompatibleWithType(serializer, type);
 
             if (_cache.TryAdd(type, serializer))
             {
@@ -178,7 +180,7 @@ private IBsonSerializer CreateSerializer(Type type)
             throw new BsonSerializationException(message);
         }
 
-        private void EnsureRegisteringASerializerForThisTypeIsAllowed(IBsonSerializer serializer, Type type)
+        private void EnsureRegisteringASerializerForThisTypeIsAllowed(Type type)
         {
             var typeInfo = type.GetTypeInfo();
             if (typeof(BsonValue).GetTypeInfo().IsAssignableFrom(type))
@@ -191,9 +193,13 @@ private void EnsureRegisteringASerializerForThisTypeIsAllowed(IBsonSerializer se
                 var message = string.Format("Generic type {0} has unassigned type parameters.", BsonUtils.GetFriendlyTypeName(type));
                 throw new ArgumentException(message, "type");
             }
+        }
+
+        private void EnsureSerializerIsCompatibleWithType(IBsonSerializer serializer, Type type)
+        {
             if (!serializer.ValueType.IsAssignableFrom(type))
             {
-                throw new BsonSerializationException($"A serializer for {BsonUtils.GetFriendlyTypeName(serializer.ValueType)} cannot be registered for type {BsonUtils.GetFriendlyTypeName(type)}.");
+                throw new ArgumentException($"A serializer for {BsonUtils.GetFriendlyTypeName(serializer.ValueType)} cannot be registered for type {BsonUtils.GetFriendlyTypeName(type)}.");
             }
         }
     }

tests/MongoDB.Bson.Tests/Serialization/BsonSerializerRegistryTests.cs

@@ -105,8 +105,8 @@ public void RegisterSerializer_should_throw_when_type_and_serializer_do_not_matc
 
             var exception = Record.Exception(() => subject.RegisterSerializer(typeof(long), intSerializer));
 
-            exception.Should().BeOfType<BsonSerializationException>();
-            exception.Message.Should().Contain("A serializer for Int32 cannot be registered for type Int64.");
+            exception.Should().BeOfType<ArgumentException>();
+            exception.Message.Should().Be("A serializer for Int32 cannot be registered for type Int64.");
         }
 
         [Fact]
@@ -117,8 +117,8 @@ public void TryRegisterSerializer_should_throw_when_type_and_serializer_do_not_m
 
             var tryException = Record.Exception(() => subject.TryRegisterSerializer(typeof(long), intSerializer));
 
-            tryException.Should().BeOfType<BsonSerializationException>();
-            tryException.Message.Should().Contain("A serializer for Int32 cannot be registered for type Int64.");
+            tryException.Should().BeOfType<ArgumentException>();
+            tryException.Message.Should().Be("A serializer for Int32 cannot be registered for type Int64.");
         }
 
         [Fact]
@@ -153,17 +153,7 @@ private class Person
         private class PeopleSerializer : SerializerBase<IEnumerable<Person>>
         {
             public override void Serialize(BsonSerializationContext context, BsonSerializationArgs args, IEnumerable<Person> value)
-            {
-                context.Writer.WriteStartArray();
-                foreach (var person in value)
-                {
-                    context.Writer.WriteStartDocument();
-                    context.Writer.WriteName("Name");
-                    context.Writer.WriteString(person.Name);
-                    context.Writer.WriteEndDocument();
-                }
-                context.Writer.WriteEndArray();
-            }
+                => throw new NotImplementedException();
 
             public override IEnumerable<Person> Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
                 => throw new NotImplementedException();