schema/field: add GoType support for enum fields (#638)

schema/field/field.go

@@ -732,6 +732,22 @@ func (b *enumBuilder) Annotations(annotations ...Annotation) *enumBuilder {
 	return b
 }
 
+// EnumValues defines the interface for getting the enum values.
+type EnumValues interface {
+	Values() []string
+}
+
+// GoType overrides the default Go type with a custom one.
+//
+//	field.Enum("enum").
+//		GoType(role.Enum("role"))
+//
+func (b *enumBuilder) GoType(ev EnumValues) *enumBuilder {
+	b.Values(ev.Values()...)
+	b.desc.goType(ev, stringType)
+	return b
+}
+
 // Descriptor implements the ent.Field interface by returning its descriptor.
 func (b *enumBuilder) Descriptor() *Descriptor {
 	return b.desc

schema/field/field_test.go

@@ -326,6 +326,12 @@ func TestField_Tag(t *testing.T) {
 	assert.Equal(t, `json:"expired,omitempty"`, fd.Tag)
 }
 
+type Role string
+
+func (Role) Values() []string {
+	return []string{"admin", "owner"}
+}
+
 func TestField_Enums(t *testing.T) {
 	fd := field.Enum("role").
 		Values(
@@ -338,6 +344,15 @@ func TestField_Enums(t *testing.T) {
 	assert.Equal(t, "role", fd.Name)
 	assert.Equal(t, map[string]string{"admin": "admin", "master": "master", "user": "user"}, fd.Enums)
 	assert.Equal(t, "user", fd.Default)
+
+	fd = field.Enum("role").GoType(Role("")).Descriptor()
+	assert.NoError(t, fd.Err())
+	assert.Equal(t, "field_test.Role", fd.Info.Ident)
+	assert.Equal(t, "github.com/facebookincubator/ent/schema/field_test", fd.Info.PkgPath)
+	assert.Equal(t, "field_test.Role", fd.Info.String())
+	assert.False(t, fd.Info.Nillable)
+	assert.False(t, fd.Info.ValueScanner())
+	assert.Equal(t, map[string]string{"admin": "admin", "owner": "owner"}, fd.Enums)
 }
 
 func TestField_UUID(t *testing.T) {