From 45198b5115ca1fdc745710459bf4188f70d0f91e Mon Sep 17 00:00:00 2001
From: Renat Mennanov <renat@mennanov.com>
Date: Fri, 3 Sep 2021 14:19:30 -0700
Subject: [PATCH] Fixes #21: incorrect behavior with Anypb.

---
 copy.go            | 21 ++++++++++++---------
 copy_proto_test.go |  6 ++++--
 2 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/copy.go b/copy.go
index 022e6bc..9ec304f 100644
--- a/copy.go
+++ b/copy.go
@@ -84,33 +84,36 @@ func structToStruct(filter FieldFilter, src, dst *reflect.Value, userOptions *op
 		}
 
 		if srcAny, ok := src.Interface().(*anypb.Any); ok {
-			dstAny, ok := src.Interface().(*anypb.Any)
+			dstAny, ok := dst.Interface().(*anypb.Any)
 			if !ok {
 				return errors.Errorf("dst type is %s, expected: %s ", dst.Type(), "*any.Any")
 			}
 
-			newSrcProto, err := srcAny.UnmarshalNew()
+			srcProto, err := srcAny.UnmarshalNew()
 			if err != nil {
 				return errors.WithStack(err)
 			}
-			newSrc := reflect.ValueOf(newSrcProto)
+			srcProtoValue := reflect.ValueOf(srcProto)
 
-			newDstProto, err := dstAny.UnmarshalNew()
+			if dstAny.GetTypeUrl() == "" {
+				dstAny.TypeUrl = srcAny.GetTypeUrl()
+			}
+			dstProto, err := dstAny.UnmarshalNew()
 			if err != nil {
 				return errors.WithStack(err)
 			}
-			newDst := reflect.ValueOf(newDstProto)
+			dstProtoValue := reflect.ValueOf(dstProto)
 
-			if err := structToStruct(filter, &newSrc, &newDst, userOptions); err != nil {
+			if err := structToStruct(filter, &srcProtoValue, &dstProtoValue, userOptions); err != nil {
 				return err
 			}
 
-			newSrcAny := new(anypb.Any)
-			if err := newSrcAny.MarshalFrom(newDst.Interface().(proto.Message)); err != nil {
+			newDstAny := new(anypb.Any)
+			if err := newDstAny.MarshalFrom(dstProtoValue.Interface().(proto.Message)); err != nil {
 				return errors.WithStack(err)
 			}
 
-			dst.Set(reflect.ValueOf(newSrcAny))
+			dst.Set(reflect.ValueOf(newDstAny))
 			break
 		}
 
diff --git a/copy_proto_test.go b/copy_proto_test.go
index 03d786d..573eece 100644
--- a/copy_proto_test.go
+++ b/copy_proto_test.go
@@ -129,7 +129,8 @@ func TestStructToStruct_Proto(t *testing.T) {
 func TestStructToStruct_ExistingAnyPreserved(t *testing.T) {
 	existingExtraUser := &testproto.User{
 		Id:       42,
-		Username: "username",
+		Username: "emily",
+		Role:     testproto.Role_REGULAR,
 	}
 	existingExtraUserAny, err := anypb.New(existingExtraUser)
 	require.NoError(t, err)
@@ -145,7 +146,8 @@ func TestStructToStruct_ExistingAnyPreserved(t *testing.T) {
 	require.NoError(t, err)
 	assert.Equal(t, testUserFull.Id, extraUser.Id)
 	assert.Equal(t, testUserFull.Avatar.OriginalUrl, extraUser.Avatar.OriginalUrl)
-	assert.Equal(t, "username", extraUser.Username)
+	assert.Equal(t, existingExtraUser.Username, extraUser.Username)
+	assert.Equal(t, existingExtraUser.Role, extraUser.Role)
 }
 
 func TestStructToStruct_PartialProtoSuccess(t *testing.T) {