Fail new tree creation when layer files exist

prover/prover.go

@@ -19,6 +19,7 @@
 	mshared "github.com/spacemeshos/merkle-tree/shared"
 	"go.uber.org/zap"
 	"go.uber.org/zap/zapcore"
+	"golang.org/x/exp/maps"
 
 	"github.com/spacemeshos/poet/logging"
 	"github.com/spacemeshos/poet/shared"
@@ -119,7 +120,17 @@
 	)
 }
 
+// Create a new merkle tree for proof generation.
 func makeProofTree(treeCfg TreeConfig, merkleHashFunc merkle.HashFunc) (*merkle.Tree, *cache.Writer, error) {
+	// Make sure there are no existing layer files.
+	layersFiles, err := getLayersFiles(treeCfg.Datadir)
+	if err != nil {
+		return nil, nil, err
+	}
+	if len(layersFiles) > 0 {
+		return nil, nil, fmt.Errorf("datadir is not empty. %v layer files exist", maps.Values(layersFiles))
+	}
+
 	minMemoryLayer := max(treeCfg.MinMemoryLayer, LowestMerkleMinMemoryLayer)
 	treeCache := cache.NewWriter(
 		cache.Combine(
@@ -136,6 +147,7 @@
 	return tree, treeCache, nil
 }
 
+// Recover merkle tree from existing cache files.
 func makeRecoveryProofTree(
 	ctx context.Context,
 	treeCfg TreeConfig,

prover/prover_test.go

@@ -148,3 +148,23 @@ func TestTreeRecovery(t *testing.T) {
 		test(t, 1000)
 	})
 }
+
+func TestNewTreeFailOnDirectoryNotEmpty(t *testing.T) {
+	t.Parallel()
+
+	r := require.New(t)
+	// Create a tree and add some nodes to it
+	treeCfg := TreeConfig{
+		MinMemoryLayer: 3,
+		Datadir:        t.TempDir(),
+	}
+	merklehashFuncFunc := hash.GenMerkleHashFunc([]byte{})
+	tree, treeCache, err := makeProofTree(treeCfg, merklehashFuncFunc)
+	r.NoError(err)
+	r.NoError(tree.AddLeaf(bytes.Repeat([]byte{7}, 32)))
+	treeCache.Close()
+
+	// try to create a new tree in the same directory
+	_, _, err = makeProofTree(treeCfg, merklehashFuncFunc)
+	r.Error(err)
+}