Setting PropertyNamingPolicy to CamelCase caused deserialization to fail

[aaronpowell]

This was tested on the v4 branch at commit d706a6d, but can be replicated with 4.0.0-preview3

I have a CosmosDB with documents that have camel-cased fields like id, modelType, state, etc. and want to have them deserialized to .NET types with standard .NET naming conventions of Id, ModelType, State, etc.

When setting the PropertyNamingPolicy on the CosmosClientOptions the application fails to run, with an error in private IReadOnlyList<T> CreateQueryFeedResponseWithSerializer<T> with the feedResponse.Value being null.

Here's a sample document:

{
  "id": "abc",
  "modelType": "game",
  "state": "WaitingForPlayers"
}

And working code:

    class Game
    {
        public string id { get; set; }
        public string modelType { get; set; }
        public string state { get; set; }
    }

    class Program
    {
        async static Task Main(string[] args)
        {
            var connStr = "...";

            var ops = new CosmosClientOptions
            {
                DefaultSerializerOptions = new Azure.Cosmos.Serialization.CosmosSerializationOptions
                {
                    PropertyNamingPolicy = Azure.Cosmos.Serialization.CosmosPropertyNamingPolicy.Default
                }
            };

            var client = new CosmosClient(connStr, ops);

            var qd = new QueryDefinition("SELECT * from c where c.modelType = 'Game'");

            var container = client.GetDatabase("trivia").GetContainer("game");

            var res = container.GetItemQueryResultsAsync<Game>(qd);

            await foreach(var item in res)
            {
                Console.WriteLine($"Game {item.id} is in state {item.state}");
            }

            Console.ReadLine();
        }
    }

But if I change it to this, it'll error:

    class Game
    {
        public string Id { get; set; }
        public string ModelType { get; set; }
        public string State { get; set; }
    }

    class Program
    {
        async static Task Main(string[] args)
        {
            var connStr = "...";

            var ops = new CosmosClientOptions
            {
                DefaultSerializerOptions = new Azure.Cosmos.Serialization.CosmosSerializationOptions
                {
                    PropertyNamingPolicy = Azure.Cosmos.Serialization.CosmosPropertyNamingPolicy.CamelCase
                }
            };

            var client = new CosmosClient(connStr, ops);

            var qd = new QueryDefinition("SELECT * from c where c.modelType = 'Game'");

            var container = client.GetDatabase("trivia").GetContainer("game");

            var res = container.GetItemQueryResultsAsync<Game>(qd);

            await foreach(var item in res)
            {
                Console.WriteLine($"Game {item.Id} is in state {item.State}");
            }

            Console.ReadLine();
        }
    }

Is this not how you're meant to override serialisation?