Merge pull request #5322 from oasisprotocol/kostko/stable/22.2.x/back…

…port-5321

[BACKPORT/22.2.x] go/storage/mkvs: Fix commit of nil entries

.changelog/5321.bugfix.md

@@ -0,0 +1 @@
+go/storage/mkvs: Fix commit of nil entries

go/storage/mkvs/commit.go

@@ -111,7 +111,7 @@ func (t *tree) commitWithHooks(
 		}
 
 		log = append(log, writelog.LogEntry{Key: entry.key, Value: entry.value})
-		if len(entry.value) == 0 {
+		if entry.value == nil {
 			logAnns = append(logAnns, writelog.LogEntryAnnotation{InsertedNode: nil})
 		} else {
 			logAnns = append(logAnns, writelog.LogEntryAnnotation{InsertedNode: entry.insertedLeaf})

go/storage/mkvs/tree_test.go

@@ -1165,6 +1165,47 @@ func testSize(t *testing.T, ndb db.NodeDB, factory NodeDBFactory) {
 	require.True(t, newSize > size, "Size should be greater than before")
 }
 
+func testEmptyValueWriteLog(t *testing.T, ndb db.NodeDB, factory NodeDBFactory) {
+	ctx := context.Background()
+
+	// Populate the tree.
+	tree := New(nil, ndb, node.RootTypeState)
+	err := tree.Insert(ctx, []byte("foo"), []byte("bar"))
+	require.NoError(t, err, "Insert")
+	err = tree.Insert(ctx, []byte("bar"), []byte(""))
+	require.NoError(t, err, "Insert")
+	writeLog, rootHash, err := tree.Commit(ctx, testNs, 0)
+	require.NoError(t, err, "Commit")
+
+	// Ensure no nil entries returned.
+	for _, entry := range writeLog {
+		require.NotNil(t, entry.Value)
+	}
+
+	startRoot := node.Root{
+		Namespace: testNs,
+		Version:   0,
+		Type:      node.RootTypeState,
+	}
+	startRoot.Hash.Empty()
+
+	endRoot := node.Root{
+		Namespace: testNs,
+		Hash:      rootHash,
+		Version:   0,
+		Type:      node.RootTypeState,
+	}
+
+	// Fetch write log from database.
+	wli, err := ndb.GetWriteLog(ctx, startRoot, endRoot)
+	require.NoError(t, err, "GetWriteLog")
+	writeLog = foldWriteLogIterator(t, wli)
+
+	for _, entry := range writeLog {
+		require.NotNil(t, entry.Value)
+	}
+}
+
 func testMergeWriteLog(t *testing.T, ndb db.NodeDB, factory NodeDBFactory) {
 	ctx := context.Background()
 
@@ -2224,6 +2265,7 @@ func testBackend(
 		{"DebugDump", testDebugDumpLocal},
 		{"OnCommitHooks", testOnCommitHooks},
 		{"CommitNoPersist", testCommitNoPersist},
+		{"EmptyValueWriteLog", testEmptyValueWriteLog},
 		{"MergeWriteLog", testMergeWriteLog},
 		{"HasRoot", testHasRoot},
 		{"GetRootsForVersion", testGetRootsForVersion},