Union type strips underscore in interface declaration, but not in method implementation

[ZackKorman]

What happened?

We are trying to update from 0.7.2 to 0.8.3, and our schema has types like Content_User and Content_Post. Previously these would generate Go structs of the same name (Content_User and Content_Post), but now they generate structs without the underscore (ContentUser and ContentPost).

I don’t see that documented anywhere, but it’s not a major problem. I can make the changes to handle that. However, we also have a union type defined in the schema: union Content_Child = Content_User | Content_Post, which generates:

type ContentChild interface {
	IsContentChild()
}
...
func (ContentUser) IsContent_Child() {}

func (ContentPost) IsContent_Child() {}

As a result, neither type satisfies ContentChild.

What did you expect?

I expected the underscore to get stripped from the IsContent_Child method, given that the interface refers to IsContentChild.

Minimal graphql.schema and models to reproduce

Schema:

type Content_User {
  foo: String
}

type Content_Post {
  foo: String
}

union Content_Child = Content_User | Content_Post

versions

• gqlgen version? v0.8.3
• go version? v1.12.4
• dep or go modules? go modules

[ZackKorman]

I don't have any experience working with the internals of gqlgen, but I feel this commit might have introduced this bug, in changing Is{{.Name }}() to Is{{.Name|go }}(): de3b7cb#diff-6d3fce6819ce4ba7bdbb9fd106746d78

The declaration uses Is{{.Name|go }}():

gqlgen/plugin/modelgen/models.gotpl

Lines 17 to 19 in 8e66832

	type {{.Name|go }} interface {
	Is{{.Name|go }}()
	}

But the implementation uses Is{{ $iface }}():

gqlgen/plugin/modelgen/models.gotpl

Lines 33 to 35 in 8e66832

	{{- range $iface := .Implements }}
	func ({{ $model.Name|go }}) Is{{ $iface }}() {}
	{{- end }}

I am not sure if this helps any.