[4.0.0 backport] CBG-4908: fix for panic in CheckProposedVersion for legacy revision case (#7803)

Co-authored-by: Gregory Newman-Smith <[email protected]>

Author: torcolvin

db/crud.go

@@ -3688,6 +3688,9 @@ func (db *DatabaseCollectionWithUser) CheckProposedVersion(ctx context.Context,
 	} else if previousRevFormat == "revTreeID" && syncData.GetRevTreeID() == previousRev {
 		// Non-conflicting update, client's previous legacy revTreeID is server's currentRev
 		return ProposedRev_OK, ""
+	} else if hlv == nil {
+		// no HLV on this doc in SGW so if previousRev didn't match current rev then it is a conflict
+		return ProposedRev_Conflict, syncData.GetRevTreeID()
 	} else if previousRevFormat == "version" && localDocCV == previousVersion {
 		// Non-conflicting update, client's previous version is server's CV
 		return ProposedRev_OK, ""

rest/blip_api_crud_test.go

@@ -3568,6 +3568,52 @@ func TestBlipPullConflict(t *testing.T) {
 	})
 }
 
+func TestPushHLVOntoLegacyRev(t *testing.T) {
+	t.Skip("CBG-4909 skipping due to conflict resolution not yet implemented for CBL rev tree")
+
+	btcRunner := NewBlipTesterClientRunner(t)
+	btcRunner.SkipSubtest[RevtreeSubtestName] = true // revtree subtest not relevant to this test
+	btcRunner.Run(func(t *testing.T) {
+		// Steps:
+		// 1. Rev 1-abc is created on SGW
+		// 2. Client pulls this revision (one shot)
+		// 3. Doc is mutated on SGW to get 2-abc (legacy rev only)
+		// 4. Doc is updated on CBL to get 100@CBL1 (HLV)
+		// 5. Client attempts to push this doc update
+		rt := NewRestTester(t,
+			&RestTesterConfig{
+				SyncFn: channels.DocChannelsSyncFunction,
+			})
+		defer rt.Close()
+
+		docID := SafeDocumentName(t, t.Name())
+
+		const alice = "alice"
+		rt.CreateUser(alice, []string{"ABC"})
+
+		opts := &BlipTesterClientOpts{Username: alice}
+		client := btcRunner.NewBlipTesterClientOptsWithRT(rt, opts)
+
+		// create legacy doc on rt and have CBL pull it
+		doc := rt.CreateDocNoHLV(docID, db.Body{"channels": []string{"ABC"}})
+		btcRunner.StartOneshotPull(client.id)
+
+		docInitVersion := doc.ExtractDocVersion()
+		btcRunner.WaitForVersion(client.id, docID, docInitVersion)
+
+		// update doc again in legacy mode on rt
+		_ = rt.CreateDocNoHLV(docID, db.Body{"channels": []string{"ABC"}, "_rev": docInitVersion.RevTreeID})
+
+		// update doc on client to have vv given to it and attempt to push it
+		newVersion := btcRunner.AddRev(client.id, docID, &docInitVersion, []byte(`{"channels": ["ABC"]}`))
+
+		btcRunner.StartPush(client.id)
+		btcRunner.StartPull(client.id)
+
+		rt.WaitForVersion(docID, newVersion)
+	})
+}
+
 func TestTombstoneCount(t *testing.T) {
 	base.SetUpTestLogging(t, base.LevelDebug, base.KeyAll)
 	rtConfig := RestTesterConfig{