Mvc: ApiExplorer: ApiDescriptionGroup.GroupName is always empty

[bugproof]

I'm using IApiDescriptionGroupCollectionProvider to get information about the API. But ApiDescriptionGroup.GroupName is always empty when iterating over group collection.

According to this post https://andrewlock.net/introduction-to-the-apiexplorer-in-asp-net-core/ it is supposed to return controller name?

Now because this doesn't work I have to group all the ApiDescriptions by controller manually.

[pranavkm]

It's controlled by the GroupName property on ApiExplorerSettingsAttribute. If you look at the blog post, the value is explicitly set using the attribute:

[Route("api/[controller]")]
[ApiExplorerSettings(IgnoreApi = false, GroupName = nameof(ValuesController))]
public class ValuesController : Controller  

[pranavkm]

@glennc \ @rynowak we could consider defaulting this to a prettified controller name for ApiController instances with an ApiBehaviorOption to suppress it.
@tuespetre does something similar in https://github.com/aspnet/Mvc/issues/5179.

[rynowak]

I think want need to understand why that's important 😆 What do the swagger frameworks use it for?

[pranavkm]

It's supposed to translate in to tags which you could then logically group operations by - https://swagger.io/docs/specification/2-0/grouping-operations-with-tags. Although scanning the code, it doesn't look like think either NSwag or Swashbuckle uses this property today.

[rynowak]

But group name is a single thing - not a set of tags. We also intended it to be used for things like versioning.

[pranavkm]

Right. My suggestion was for consumers to use it as a tag value when available.

We also intended it to be used for things like versioning.

Ok. I guess we can solve exposing the notion of ApiDescription.Tags independent of this (and nobody's clamored for it as yet).

[pranavkm]

Closing for now until we figure out how this field needs to play with versioning and \ or tags. @lecoque for the time being, I'd recommend using the ApiExplorerSettingsAttribute to set it. Alternatively, you could consider an application model convention to do this for all controllers. https://github.com/aspnet/Mvc/issues/5179 has an example of setting this up.