fix(introspection): support @deprecated directive on field arguments

[AlexanderArvidsson]

Field arguments are currently not introspected as deprecated due to a typo in the field arguments definition in the introspection code. It uses the directives from the field instead of the directives on the field argument:

		for _, arg := range f.Arguments {
			args = append(args, InputValue{
				Type:         WrapTypeFromType(t.schema, arg.Type),
				Name:         arg.Name,
				description:  arg.Description,
				DefaultValue: defaultValue(arg.DefaultValue),
-				deprecation:  f.Directives.ForName("deprecated"),
+				deprecation:  arg.Directives.ForName("deprecated"),
			})

The GraphQL spec was updated in September to allow deprecation on field arguments, and gqlgen seems to have followed, though not working due to the above typo.

I have also added tests, although I must admit I am not entirely sure what the difference is between testserver/singlefile and testserver/followschema. However, I mimicked what I saw from other tests.

I also added introspection tests in the integration/ folder, but running the GraphQL codegen generated code that was unrelated to my changes (perhaps these have not been re-generated for a while, and GraphQL codegen changed?), so I have not included that. I'm open to add those changes to this PR if you're OK with extra stuff being added by codegen.

I have:

• Added tests covering the bug / feature (see testing)
• Updated any relevant documentation (see docs)

[coveralls]

coverage: 0.0%. remained the same
when pulling e015421 on AlexanderArvidsson:fix/field-argument-deprecation
into 9da91b3 on 99designs:master.

[AlexanderArvidsson]

Fixed the linting, I did not see it because I had v1 of golangci-lint instead of v2 which caused it to not run in Neovim 😓

[StevenACoffman]

Thanks for this! I could also use help updating https://github.com/vektah/gqlparser (which gqlgen relies on) to the latest spec update.

[AlexanderArvidsson]

Thanks for this! I could also use help updating https://github.com/vektah/gqlparser (which gqlgen relies on) to the latest spec update.

I might have a look if I find some time, am happy to help!
This one case I only found when deprecating a field and wondering why my introspected schema didn't include it.

[StevenACoffman]

@AlexanderArvidsson If you get a chance, vektah/gqlparser#401 is where I started to update it, and then there are just various test failures to work through. Anything you can contribute would be a huge help!