Stub generation

[vektah]

The tests on code generation are getting very long, relying on a large object defined at the bottom of a ~1000 line file.

This adds a codegen plugin that generates a Stub that fits the resolver interface, for the generated server it looks like this:

type Stub struct {
	QueryResolver struct {
		User                   func(ctx context.Context, id int) (User, error)
		NullableArg            func(ctx context.Context, arg *int) (*string, error)
		DirectiveArg           func(ctx context.Context, arg string) (*string, error)
		DirectiveNullableArg   func(ctx context.Context, arg *int, arg2 *int) (*string, error)
		// lots of other unimportant fields removed
	}
	SubscriptionResolver struct {
		Updated     func(ctx context.Context) (<-chan string, error)
		InitPayload func(ctx context.Context) (<-chan string, error)
	}
	UserResolver struct {
		Friends func(ctx context.Context, obj *User) ([]User, error)
	}
}

which now allows each test to easily define the one or two resolvers it expects to hit simply:

resolvers := &Stub{}
resolvers.QueryResolver.Valid = func(ctx context.Context) (s string, e error) {
	return "Ok", nil
}

resolvers.QueryResolver.ErrorBubble = func(ctx context.Context) (i *Error, e error) {
	return &Error{ID: "E1234"}, nil
}

srv := httptest.NewServer(handler.GraphQL(NewExecutableSchema(Config{Resolvers: resolvers})))
c := client.New(srv.URL)

And everything else will panic.