Unable to override the JsonSerializer when using ConfigureFunctionsWebApplication for CosmoDb Input bindings

[JayChase]

Description

Azure Function App issue: setting JsonSerializerOptions not working with Cosmos input bindings

Issue

Custom JSON Serialization options are ignored when deserializing CosmosDB input bindings. The main issue for my project is this then leads to Enums in third party classes (Ms Graph SDK) causing an exception.

This repo recreates the issue.

This issue us related to the FromBody issue here.

Refs

• Documentation followed for Customizing JSON serialization

• Related issues: Unable to override the JsonSerializer when using ConfigureFunctionsWebApplication

• Note adding the JsonConverter attribute is not an option as the classes are third party (Kiota generated).

Steps to reproduce

Create a dotnet isolated Function App with a fucntion that has CosmosDb input binding...

Program.cs (the config)

var host = new HostBuilder()
       .ConfigureFunctionsWebApplication((IFunctionsWorkerApplicationBuilder builder) =>
    {
        builder.Services.Configure<JsonSerializerOptions>(jsonSerializerOptions =>
        {
            jsonSerializerOptions.PropertyNamingPolicy = JsonNamingPolicy.CamelCase;
            jsonSerializerOptions.DictionaryKeyPolicy = JsonNamingPolicy.CamelCase;
            jsonSerializerOptions.WriteIndented = true;
            jsonSerializerOptions.Converters.Add(new JsonStringEnumConverter(JsonNamingPolicy.CamelCase));
        });
    })
    .ConfigureServices(services =>
    {
        services.AddApplicationInsightsTelemetryWorkerService();
        services.ConfigureFunctionsApplicationInsights();
    })
    .Build();

Message.cs (a class with an enum property)

public enum Sentiment
{
    Positive,
    Neutral,
    Negative
}

public class Message
{

    public string Id { get; set; } = string.Empty;

    //[JsonConverter(typeof(JsonStringEnumConverter))]
    public Sentiment? Sentiment { get; set; }
}

MessageFromBinding.cs (the http triggered function with the CosmosDb input binding)

[Function("MessageFromBinding")]
public IActionResult Run([HttpTrigger(AuthorizationLevel.Function, "post", Route = "messageFromBinding/{messageId}")] HttpRequest req,
    [CosmosDBInput(
databaseName: "%COSMOS_DB_NAME%",
containerName: "%COSMOS_DB_CONTAINER_NAME%",
Connection  = "COSMOS_DB_CONNECTION",
Id = "{messageId}",
PartitionKey = "{messageId}")] Message cosmosDbMessage)
{
    _logger.LogInformation("cosmosDbMessage received: {@cosmosDbMessage}", cosmosDbMessage);
    _logger.LogInformation("C# HTTP trigger function processed a request.");
    return new OkObjectResult("Welcome to Azure Functions!");
}

The error

Error:System.Text.Json.JsonException: The JSON value could not be converted to System.Nullable`1[FuncJsonIssue.Models.Sentiment].

[liliankasem]

It looks like we don't use the worker serializer in the cosmos extension

azure-functions-dotnet-worker/extensions/Worker.Extensions.CosmosDB/src/CosmosDBConverter.cs

Line 116 in bf563c4

return (await JsonSerializer.DeserializeAsync(item.Content, targetType, _serializerOptions))!;

But we do in blobs, for example:

azure-functions-dotnet-worker/extensions/Worker.Extensions.Storage.Blobs/src/BlobStorageConverter.cs

Line 214 in bf563c4

return _workerOptions?.Value?.Serializer?.Deserialize(content, targetType, CancellationToken.None);

I'm not sure if Fabio's guidance applies here or not, but if it doesn't help, I think this will just have to be a fix made to the cosmos extension.

[JayChase]

Hi @liliankasem. Thank you for looking at this. I have tried the workaround and it does not help.