Can't use isolated model with RabbitMQ extension for SharePoint WebHooks

[NinjaSciurus]

What version of .NET does your existing project use?

.NET 6

What version of .NET are you attempting to target?

.NET 8

Description

In the in-process model the RabbitMQ extension used an IAsyncCollector interface to send messages, injected into the function's Run method as a call parameter (this is still part of the official documentation). This allowed to use an Azure Function as SharePoint WebHook receiver, since registering a new SharePoint WebHook requires the function to return a validationToken as a simple string to the caller (SharePoint).

Now, the isolated model only supports the RabbitMQOutputAttribute which defines the return value of the function to be pushed to RabbitMQ without exception. By this design, the RabbitMQ extension became unusable in a SharePoint WebHook Azure Function using the recommended isolated worker model.

Am I missing something or is it actually not possible anymore to use the RabbitMQ extension in a SharePoint WebHook?

Project configuration and dependencies

This is our current mid-migration .NET 8 .csproj file:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net8.0</TargetFramework>
    <AzureFunctionsVersion>v4</AzureFunctionsVersion>
    <OutputType>Exe</OutputType>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>disable</Nullable>
  </PropertyGroup>
  <ItemGroup>
    <FrameworkReference Include="Microsoft.AspNetCore.App" />
    <PackageReference Include="Microsoft.ApplicationInsights.WorkerService" Version="2.23.0" /> 
    <PackageReference Include="Microsoft.Azure.Functions.Worker.ApplicationInsights" Version="2.0.0" /> 
    <PackageReference Include="Microsoft.Azure.Functions.Worker" Version="2.1.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Http" Version="3.3.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Http.AspNetCore" Version="2.0.2" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.RabbitMQ" Version="2.1.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Sdk" Version="2.0.5" />
    <PackageReference Include="Newtonsoft.Json" Version="13.0.4" />
  </ItemGroup>
  <ItemGroup>
    <None Update="host.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="local.settings.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
      <CopyToPublishDirectory>Never</CopyToPublishDirectory>
    </None>
  </ItemGroup>
  <ItemGroup>
    <Using Include="System.Threading.ExecutionContext" Alias="ExecutionContext" />
  </ItemGroup>
</Project>
`

### Link to a repository that reproduces the issue

_No response_

[satvu]

@aloiva is this something you could help look into?

[aloiva]

@NinjaSciurus , I'm not familiar with using SharePoint Webhooks but looks like you want to use multiple output bindings, one of them being RabbitMQ output and another being an http return response.
If it is the intention, dotnet-isolated lets you have multiple output bindings. I put together a sample for your use case:

public class OutputType
{
    [RabbitMQOutput(ConnectionStringSetting = "RabbitMqConnection", QueueName = "myqueue")]
    public string RabbitMQMessage { get; set; } = string.Empty;

    [HttpResult]
    public HttpResponseData HttpResponse { get; set; } = null!;
}
public class HttpTrigger1
{
    [Function("HttpTrigger1")]
    public async Task<OutputType> Run(
        [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post")] HttpRequestData req)
    {
        var response = req.CreateResponse(HttpStatusCode.OK);
        await response.WriteStringAsync("Sent token validation");
        
        return new OutputType()
        {
            HttpResponse = response,
            RabbitMQMessage = "Sent message to RabbitMQ"
        };
    }
}

[NinjaSciurus]

@aloiva Oh wow! I was not aware something like this is possible, thank you very much for the sample! I will definitely try this and check back to hopefully close this issue.