Amazon.Lambda.Serialization.SystemTextJson.LambdaJsonSerializer uses different property casing than Amazon.Lambda.Serialization.Json.JsonSerializer

It appears that the default casing behavior has changed between Amazon.Lambda.Serialization.Json.JsonSerializer and Amazon.Lambda.Serialization.SystemTextJson.LambdaJsonSerializer.

Here is some sample code to test the difference:

// create an instance to serialize
var record = new Record {
    Foo = "Hello world!"
};

// show serialization with original Lambda serializer based on Newtonsoft.Json
var oldSerializer = SerializeWith(record, new Amazon.Lambda.Serialization.Json.JsonSerializer());
Console.WriteLine($"Amazon.Lambda.Serialization.Json.JsonSerializer: {oldSerializer}");

// show serialization with new Lambda serializer based on System.Text.Json
var newSerializer = SerializeWith(record, new Amazon.Lambda.Serialization.SystemTextJson.LambdaJsonSerializer());
Console.WriteLine($"Amazon.Lambda.Serialization.SystemTextJson.LambdaJsonSerializer: {newSerializer}");

// show serialization with System.Json.Text
var jsonTextSerializer = System.Text.Json.JsonSerializer.Serialize<Record>(record);
Console.WriteLine($"System.Text.Json.JsonSerializer: {jsonTextSerializer}");

// local functions
string SerializeWith<T>(T value, Amazon.Lambda.Core.ILambdaSerializer serializer) {
    using var buffer = new MemoryStream();
    serializer.Serialize<T>(value, buffer);;
    return System.Text.Encoding.UTF8.GetString(buffer.ToArray());
}

The above code produces the following output:

Amazon.Lambda.Serialization.Json.JsonSerializer: {"Foo":"Hello world!"}
Amazon.Lambda.Serialization.SystemTextJson.LambdaJsonSerializer: {"foo":"Hello world!"}
System.Text.Json.JsonSerializer: {"Foo":"Hello world!"}

[Kralizek]

Is it possible to keep this issue in topic?

[panodk]

Hi there I’m encountering this problem in Step Functions after switching the lambda Tasks over to .Net 3.1 + the new serializer. It’s wreaking havoc because the output now is in camelcase so the next state machine shape tries to evaluate the new JSON using the Amazon States Language and throws a Step Function exception.

There is a a kludgy workaround for the moment. By setting the LAMBDA_NET_SERIALIZER_DEBUG=true in the environment variable, the _.options is never set in the serializer causing the case to be returned untouched. I’m not sure if that will result in other repercussions other than additional JSON being emitted into the Cloudwatch Logs. https://github.com/aws/aws-lambda-dotnet/blob/master/Libraries/src/Amazon.Lambda.Serialization.SystemTextJson/LambdaJsonSerializer.cs#L69-L90

IMO, it would be a pain to decorate all of our models with the [JsonPropertyName] decoration as our models are buried in a number of nuget libraries. Ideally I’d like the default behavior to return to the original PascalCasing as before but I’m fine with using an explicit PascalCaseLambdaJsonSerializer with the lambdas when it is called in our Step Function project.

Thanks!