move lib/go/gremlin to ent/dialect (#1192)

Summary:
Pull Request resolved: https://github.com/facebookexternal/fbc/pull/1192

Pull Request resolved: https://github.com/facebookincubator/ent/pull/11

Reviewed By: alexsn

Differential Revision: D16377224

fbshipit-source-id: 07ca7436eb9b64fbe2299568560b91466b2417ba

dialect/gremlin/encoding/graphson/error.go

@@ -0,0 +1,41 @@
+package graphson
+
+import (
+	"unsafe"
+
+	"github.com/json-iterator/go"
+	"github.com/pkg/errors"
+)
+
+// EncoderOfError returns a value encoder which always fails to encode.
+func (encodeExtension) EncoderOfError(format string, args ...interface{}) jsoniter.ValEncoder {
+	return decoratorOfError(format, args...)
+}
+
+// DecoderOfError returns a value decoder which always fails to decode.
+func (decodeExtension) DecoderOfError(format string, args ...interface{}) jsoniter.ValDecoder {
+	return decoratorOfError(format, args...)
+}
+
+func decoratorOfError(format string, args ...interface{}) errorCodec {
+	err := errors.Errorf(format, args...)
+	return errorCodec{err}
+}
+
+type errorCodec struct{ error }
+
+func (ec errorCodec) Encode(_ unsafe.Pointer, stream *jsoniter.Stream) {
+	if stream.Error == nil {
+		stream.Error = ec.error
+	}
+}
+
+func (errorCodec) IsEmpty(unsafe.Pointer) bool {
+	return false
+}
+
+func (ec errorCodec) Decode(_ unsafe.Pointer, iter *jsoniter.Iterator) {
+	if iter.Error == nil {
+		iter.Error = ec.error
+	}
+}