.NET framework Isolated - The system cannot find the file specified.

[mathiasbl]

Describe the issue
The swagger endpoints do not work for projects that target .net framework isolated.

To Reproduce
Steps to reproduce the behavior:

1. Create new Azure Function project that targets .NET framework Isolated v4 with a HttpTrigger function.
2. Add Microsoft.Azure.Functions.Worker.Extensions.OpenApi package
3. Modify program.cs according to the docs

var host = new HostBuilder()
     .ConfigureFunctionsWorkerDefaults(worker => worker.UseNewtonsoftJson())

4. Add decorator the function app (Taken from the docs)

[OpenApiOperation(operationId: "greeting", tags: new[] { "greeting" }, Summary = "Greetings", Description = "This shows a welcome message.", Visibility = OpenApiVisibilityType.Important)]
     [OpenApiSecurity("function_key", SecuritySchemeType.ApiKey, Name = "code", In = OpenApiSecurityLocationType.Query)]
     [OpenApiResponseWithBody(statusCode: HttpStatusCode.OK, contentType: "text/plain", bodyType: typeof(string), Summary = "The response", Description = "This returns the response")]

6. Start project
7. Navigate to http://localhost:xxx/api/swagger/ui
8. See error: The system cannot find the file specified.

Screenshots

Environment (please complete the following information, if applicable):

• OS: Windows
• Core Tools Version: 4.0.5455 Commit hash: N/A (64-bit)
• Function Runtime Version: 4.27.5.21554

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net48</TargetFramework>
    <AzureFunctionsVersion>v4</AzureFunctionsVersion>
    <OutputType>Exe</OutputType>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.Azure.Functions.Worker" Version="1.20.1" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Http" Version="3.1.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.OpenApi" Version="1.5.1" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Sdk" Version="1.16.4" />
    <PackageReference Include="Microsoft.ApplicationInsights.WorkerService" Version="2.22.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.ApplicationInsights" Version="1.1.0" />
  </ItemGroup>
  <ItemGroup>
    <None Update="host.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="local.settings.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
      <CopyToPublishDirectory>Never</CopyToPublishDirectory>
    </None>
  </ItemGroup>
  <ItemGroup>
    <Folder Include="Properties\" />
  </ItemGroup>
</Project>

[MarcinHanczaruk]

I have exactly the same issue. Is there any fix/workaround available?

[GuidDotEmpty]

Repo can be found here:
https://github.com/GuidDotEmpty/Azure-function-NET-framework-Isolated-swagger-bug-641/tree/master

[Leibowk]

Bumping issue. Having the same problem. Would love a solution. Had this issue in our repro we inherited recently. Also tried and created a new 4.8 Function App and followed the guide here https://github.com/Azure/azure-functions-openapi-extension/blob/main/docs/enable-open-api-endpoints-out-of-proc.md and still got the same "The system cannot find the file specified. (Exception from HRESULT: 0x80070002)" error. This seems broken now.