Override template ref to be any instead of interface{}

[StevenACoffman]

This fixes #3414 so that ref template functions used when generating will consistently use any over interface{}. Linters, like revive, will flag the use of interface{} and the recommendation is to use gofmt -w -r 'interface{} -> any' to change them all to any. This PR coerces the value to always prefer any, which is a dirty hack that will probably bite me. I am not sure why the behavior is inconsistent without this change. I think somehow the template is supplied with $type.GO inconsistently (despite my putting types.Unalias seemingly all over the place in other PRs). If someone has a better idea, I would love to hear about it.

• When the type.gotpl template file pipes the $type.GO to ref here
• That calls the ref function here
• Which then calls CurrentImports.LookupType here
• Which passes the Qualifier Function using s.Lookup(i.Path() that is implemented here

When you bind a type with an Any scalar field to a go struct where that field is an interface{} it will sometimes generate the scalar marshaller (eg marshalNAny2interface) with a parameter/return type of interface{} to match that field.

I'm guessing it's a race condition sort of thing, where you're using threads to traverse the graph in parallel and generate the schema gen code. One thread sees something like an input with no go type to reference and generates the marshaller with default type of any while another thread sees the go struct with type interface{} being mapped to a field on the graph of type Any and uses that (interface{}) type when generating the marshaller.

I've made an example repo to show this happening. Just run the regen.sh script (or run go run github.com/99designs/gqlgen repeatedly) to see it sometimes generate the schema_gen.go file exactly as it's committed and sometime with a diff in the schema_gen.go file.

Example repo: https://github.com/evellior/gqlgen-test

Signed-off-by: Steve Coffman steve@khanacademy.org

[coveralls]

coverage: 73.888% (+0.02%) from 73.868%
when pulling 413b8d2 on override_interface_to_any
into 40ad172 on master.

[StevenACoffman]

@UnAfraid @evellior @giautm Not sure if any of you have any insight or better ideas. This seems to work, so I'm going to merge it and let people try it out, but I would rather understand the real root of the problem, and fix it at the source.