fix #2524 basic alias Byte was not binded properly (#2528)

* fix #2524 basic alias `Byte` was not binded properly

* add tests for defined types as []byte and []rune

Author: mstephano

_examples/scalars/.gqlgen.yml

@@ -18,3 +18,11 @@ models:
     model: github.com/99designs/gqlgen/_examples/scalars/model.Banned
   DarkMode:
     model: github.com/99designs/gqlgen/_examples/scalars/model.Preferences
+  Bytes:
+    model: "github.com/99designs/gqlgen/codegen/testserver/singlefile.Bytes"
+  Runes:
+    model: "github.com/99designs/gqlgen/_examples/scalars/model.Runes"
+  DefinedTypeBytes:
+    model: "github.com/99designs/gqlgen/_examples/scalars/external.Bytes"
+  DefinedTypeRunes:
+    model: "github.com/99designs/gqlgen/_examples/scalars/external.Runes"

_examples/scalars/external/model.go

@@ -1,13 +1,60 @@
 package external
 
+import (
+	"fmt"
+	"io"
+
+	"github.com/99designs/gqlgen/graphql"
+)
+
 type (
-	ObjectID     int
-	Manufacturer string // remote named string
-	Count        uint32 // remote named uint32
+	ObjectID      int
+	Manufacturer  string // remote named string
+	Count         uint8  // remote named uint8
+	ExternalBytes []byte
+	ExternalRunes []rune
 )
 
 const (
 	ManufacturerTesla  Manufacturer = "TESLA"
 	ManufacturerHonda  Manufacturer = "HONDA"
 	ManufacturerToyota Manufacturer = "TOYOTA"
 )
+
+func MarshalBytes(b ExternalBytes) graphql.Marshaler {
+	return graphql.WriterFunc(func(w io.Writer) {
+		_, _ = fmt.Fprintf(w, "%q", string(b))
+	})
+}
+
+func UnmarshalBytes(v interface{}) (ExternalBytes, error) {
+	switch v := v.(type) {
+	case string:
+		return ExternalBytes(v), nil
+	case *string:
+		return ExternalBytes(*v), nil
+	case ExternalBytes:
+		return v, nil
+	default:
+		return nil, fmt.Errorf("%T is not ExternalBytes", v)
+	}
+}
+
+func MarshalRunes(r ExternalRunes) graphql.Marshaler {
+	return graphql.WriterFunc(func(w io.Writer) {
+		_, _ = fmt.Fprintf(w, "%q", string(r))
+	})
+}
+
+func UnmarshalRunes(v interface{}) (ExternalRunes, error) {
+	switch v := v.(type) {
+	case string:
+		return ExternalRunes(v), nil
+	case *string:
+		return ExternalRunes(*v), nil
+	case ExternalRunes:
+		return v, nil
+	default:
+		return nil, fmt.Errorf("%T is not ExternalRunes", v)
+	}
+}