ArgumentNullException at ...SwaggerGeneratorOptions.DefaultOperationIdSelector

[icnocop]

Hi.

Upgrading from 6.1.4 to 6.1.5 causes System.ArgumentNullException: Value cannot be null. (Parameter 'source') to be thrown when generating swagger.json.

I've created a repository which can reproduce the issue here:
https://github.com/icnocop/Swashbuckle.AspNetCore.InheritanceExample

Swashbuckle.AspNetCore.SwaggerGen.SwaggerGeneratorException: Failed to generate Operation for action - WebApplication9.Controllers.AnimalsController.Post (WebApplication9). See inner exception
 ---> System.ArgumentNullException: Value cannot be null. (Parameter 'source')
   at System.Linq.ThrowHelper.ThrowArgumentNullException(ExceptionArgument argument)
   at System.Linq.Enumerable.TryGetFirst[TSource](IEnumerable`1 source, Func`2 predicate, Boolean& found)
   at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable`1 source, Func`2 predicate)
   at Swashbuckle.AspNetCore.SwaggerGen.SwaggerGeneratorOptions.DefaultOperationIdSelector(ApiDescription apiDescription)
   at Swashbuckle.AspNetCore.SwaggerGen.SwaggerGenerator.GenerateOperation(ApiDescription apiDescription, SchemaRepository schemaRepository)
   --- End of inner exception stack trace ---
   at Swashbuckle.AspNetCore.SwaggerGen.SwaggerGenerator.GenerateOperation(ApiDescription apiDescription, SchemaRepository schemaRepository)
   at Swashbuckle.AspNetCore.SwaggerGen.SwaggerGenerator.GenerateOperations(IEnumerable`1 apiDescriptions, SchemaRepository schemaRepository)
   at Swashbuckle.AspNetCore.SwaggerGen.SwaggerGenerator.GeneratePaths(IEnumerable`1 apiDescriptions, SchemaRepository schemaRepository)
   at Swashbuckle.AspNetCore.SwaggerGen.SwaggerGenerator.GetSwagger(String documentName, String host, String basePath)
   at Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.Invoke(HttpContext httpContext, ISwaggerProvider swaggerProvider)
   at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

I believe it's caused by the most recent code changes in #2173, related to #2165.

Thank you.

[domaindrivendev]

@captainsafia, @bradygaster looks like the PR to use endpoint metadata for operationId may be causing a regression with the latest release. Could you possibly take a quick look to see if there's an easy fix? Thx

[davidfowl]

I guess the EndpointMetadata collection itself is null. Should be an easy fix.