From abeccb4c760c40dff5f3b6584d1d7319288c61f6 Mon Sep 17 00:00:00 2001
From: Semir Patel <semir.patel@hashicorp.com>
Date: Mon, 15 May 2023 09:42:01 -0500
Subject: [PATCH] Support update resource with change in GroupVersion (#17330)

---
 .../grpc-external/services/resource/write.go  |  7 ++++-
 .../services/resource/write_test.go           | 31 +++++++++++++++++++
 2 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/agent/grpc-external/services/resource/write.go b/agent/grpc-external/services/resource/write.go
index d50ca1dd8b..3a365cee37 100644
--- a/agent/grpc-external/services/resource/write.go
+++ b/agent/grpc-external/services/resource/write.go
@@ -107,6 +107,7 @@ func (s *Server) Write(ctx context.Context, req *pbresource.WriteRequest) (*pbre
 		//
 		//	- CAS failures will be retried by retryCAS anyway. So the read-modify-write
 		//	  cycle should eventually succeed.
+		var mismatchError storage.GroupVersionMismatchError
 		existing, err := s.Backend.Read(ctx, storage.EventualConsistency, input.Id)
 		switch {
 		// Create path.
@@ -146,7 +147,11 @@ func (s *Server) Write(ctx context.Context, req *pbresource.WriteRequest) (*pbre
 			// TODO(spatel): Revisit owner<->resource tenancy rules post-1.16
 
 		// Update path.
-		case err == nil:
+		case err == nil || errors.As(err, &mismatchError):
+			// Allow writes that update GroupVersion.
+			if mismatchError.Stored != nil {
+				existing = mismatchError.Stored
+			}
 			// Use the stored ID because it includes the Uid.
 			//
 			// Generally, users won't provide the Uid but controllers will, because
diff --git a/agent/grpc-external/services/resource/write_test.go b/agent/grpc-external/services/resource/write_test.go
index b2960a9243..9b94ecae8b 100644
--- a/agent/grpc-external/services/resource/write_test.go
+++ b/agent/grpc-external/services/resource/write_test.go
@@ -19,6 +19,7 @@ import (
 	"github.com/hashicorp/consul/internal/resource/demo"
 	"github.com/hashicorp/consul/internal/storage"
 	"github.com/hashicorp/consul/proto-public/pbresource"
+	pbdemov1 "github.com/hashicorp/consul/proto/private/pbdemo/v1"
 	pbdemov2 "github.com/hashicorp/consul/proto/private/pbdemo/v2"
 )
 
@@ -392,6 +393,36 @@ func TestWrite_Update_NoUid(t *testing.T) {
 	require.NoError(t, err)
 }
 
+func TestWrite_Update_GroupVersion(t *testing.T) {
+	server := testServer(t)
+	client := testClient(t, server)
+
+	demo.RegisterTypes(server.Registry)
+
+	res, err := demo.GenerateV2Artist()
+	require.NoError(t, err)
+
+	rsp1, err := client.Write(testContext(t), &pbresource.WriteRequest{Resource: res})
+	require.NoError(t, err)
+
+	res = rsp1.Resource
+	res.Id.Type = demo.TypeV1Artist
+
+	// translate artistV2 to artistV1
+	var artistV2 pbdemov2.Artist
+	require.NoError(t, res.Data.UnmarshalTo(&artistV2))
+	artistV1 := &pbdemov1.Artist{
+		Name:         artistV2.Name,
+		Description:  "some awesome band",
+		Genre:        pbdemov1.Genre_GENRE_JAZZ,
+		GroupMembers: int32(len(artistV2.GroupMembers)),
+	}
+	res.Data.MarshalFrom(artistV1)
+
+	_, err = client.Write(testContext(t), &pbresource.WriteRequest{Resource: res})
+	require.NoError(t, err)
+}
+
 func TestWrite_NonCASUpdate_Success(t *testing.T) {
 	server := testServer(t)
 	client := testClient(t, server)