fix: SDL rendering for directives with input objects

[ivymarkwell]

While developing, I encountered an issue where calling Absinthe.Schema.to_sdl/1 crashes if a custom directive is defined with an input_object argument and then used on a field.

From my understanding, input_objects are valid according to the GraphQL spec (https://spec.graphql.org/October2021/#sec-Language.Directives and https://spec.graphql.org/October2021/#sec-Type-System.Directives.Validation).

Directives have a name along with a list of arguments which may accept values of any input type.

and

The argument must accept a type where [IsInputType](https://spec.graphql.org/October2021/#IsInputType())(argumentType) returns true.

This happens during the rendering of the directive's arguments in Absinthe.Schema.Notation.SDL.Render.render_value/1. This function currently doesn't seem to handle input objects as values as far as I can tell. When I inspected the render_value function, the name was getting passed as an atom which was blowing up since this wasn't a proper Inspect.Algebra document structure.

You can reproduce the error I was seeing by reverting the change in lib/absinthe/schema/notation/sdl_render.ex and running the tests. It should fail with the following (prettified) stacktrace:

** (FunctionClauseError) no function clause matching in Inspect.Algebra.concat/2

Stacktrace:
  (elixir 1.18.1) lib/inspect/algebra.ex:614: Inspect.Algebra.concat(:enabled, {:doc_cons, ": ", "true"})
  (absinthe 1.7.10) lib/absinthe/schema/notation/sdl_render.ex:406: Absinthe.Schema.Notation.SDL.Render.render_value/1
  ...
  test/absinthe/schema/sdl_render_test.exs:267: Absinthe.Schema.SdlRenderTest."test Render SDL from blueprint defined with macros"/1

Let me know if I'm misunderstanding something! I'd love to fix this on my side or improve my understanding of what's expected according to the GraphQL spec.

Thanks 🙂

[cschiewek]

This looks good to me. If you can update your branch from main and get tests passing I'll approve and merge.

[ivymarkwell]

@cschiewek I believe those tests should be fixed now. I resynced my cloned repo, did a git rebase master on this branch and applied a fix in this commit.
However, I can see now there is a 2 workflows awaiting approval status. I'm not sure how to resolve that so let me know what else I need to do. Thank you.