unixfs: fix dagTruncate to preserve node type

mfs/mfs_test.go

@@ -1136,3 +1136,43 @@ func TestTruncateAtSize(t *testing.T) {
 	}
 	fd.Truncate(4)
 }
+
+func TestTruncateAndWrite(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	ds, rt := setupRoot(ctx, t)
+
+	dir := rt.GetDirectory()
+
+	nd := dag.NodeWithData(ft.FilePBData(nil, 0))
+	fi, err := NewFile("test", nd, dir, ds)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	fd, err := fi.Open(OpenReadWrite, true)
+	defer fd.Close()
+	if err != nil {
+		t.Fatal(err)
+	}
+	for i := 0; i < 200; i++ {
+		err = fd.Truncate(0)
+		if err != nil {
+			t.Fatal(err)
+		}
+		l, err := fd.Write([]byte("test"))
+		if err != nil {
+			t.Fatal(err)
+		}
+		if l != len("test") {
+			t.Fatal("incorrect write length")
+		}
+		data, err := ioutil.ReadAll(fd)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if string(data) != "test" {
+			t.Errorf("read error at read %d, read: %v", i, data)
+		}
+	}
+}

test/sharness/t0250-files-api.sh

@@ -613,7 +613,7 @@ tests_for_files_api() {
   ROOT_HASH=QmcwKfTMCT7AaeiD92hWjnZn9b6eh9NxnhfSzN5x2vnDpt
   CATS_HASH=Qma88m8ErTGkZHbBWGqy1C7VmEmX8wwNDWNpGyCaNmEgwC
   FILE_HASH=QmQdQt9qooenjeaNhiKHF3hBvmNteB4MQBtgu3jxgf9c7i
-  TRUNC_HASH=QmdaQZbLwK5ykweGdCVovNnvBom7QhikovDUVqTPHQG4L8
+  TRUNC_HASH=QmPVnT9gocPbqzN4G6SMp8vAPyzcjDbUJrNdKgzQquuDg4
   test_files_api "($EXTRA)"
 
   test_expect_success "can create some files for testing with raw-leaves ($EXTRA)" '
@@ -629,13 +629,13 @@ tests_for_files_api() {
   ROOT_HASH=QmW3dMSU6VNd1mEdpk9S3ZYRuR1YwwoXjGaZhkyK6ru9YU
   CATS_HASH=QmPqWDEg7NoWRX8Y4vvYjZtmdg5umbfsTQ9zwNr12JoLmt
   FILE_HASH=QmRCgHeoKxCqK2Es6M6nPUDVWz19yNQPnsXGsXeuTkSKpN
-  TRUNC_HASH=QmRFJEKWF5A5FyFYZgNhusLw2UziW9zBKYr4huyHjzcB6o
+  TRUNC_HASH=QmckstrVxJuecVD1FHUiURJiU9aPURZWJieeBVHJPACj8L
   test_files_api "($EXTRA, raw-leaves)" '' --raw-leaves
 
   ROOT_HASH=QmageRWxC7wWjPv5p36NeAgBAiFdBHaNfxAehBSwzNech2
   CATS_HASH=zdj7WkEzPLNAr5TYJSQC8CFcBjLvWFfGdx6kaBrJXnBguwWeX
   FILE_HASH=zdj7WYHvf5sBRgSBjYnq64QFr449CCbgupXfBvoYL3aHC1DzJ
-  TRUNC_HASH=zdj7WYLYbka6Ydg8gZUJRLKnFBVehCADhQKBsFbNiMxZSB5Gj
+  TRUNC_HASH=zdj7Wjr8GHZonPFVCWvz2SLLo9H6MmqBxyeB34ArHfyCbmdJG
   if [ "$EXTRA" = "offline" ]; then
     test_files_api "($EXTRA, cidv1)" --cid-version=1
   fi
@@ -660,7 +660,7 @@ tests_for_files_api() {
     ROOT_HASH=zDMZof1kxEsAwSgCZsGQRVcHCMtHLjkUQoiZUbZ87erpPQJGUeW8
     CATS_HASH=zDMZof1kuAhr3zBkxq48V7o9HJZCTVyu1Wd9wnZtVcPJLW8xnGft
     FILE_HASH=zDMZof1kxbB9CvxgRioBzESbGnZUxtSCsZ18H1EUkxDdWt1DYEkK
-    TRUNC_HASH=zDMZof1kxXqKdVsVo231qVdN3hCTF5a34UuQZpzmm5K7CbRJ4u2S
+    TRUNC_HASH=zDMZof1kpH1vxK3k2TeYc8w59atCbzMzrhZonsztMWSptVro2zQa
     test_files_api "($EXTRA, blake2b-256 root)"
   fi
 

unixfs/mod/dagmodifier.go

@@ -529,7 +529,13 @@ func dagTruncate(ctx context.Context, n ipld.Node, size uint64, ds ipld.DAGServi
 	var cur uint64
 	end := 0
 	var modified ipld.Node
-	ndata := ft.NewFSNode(ft.TRaw)
+	ndata, err := ft.FSNodeFromBytes(nd.Data())
+	if err != nil {
+		return nil, err
+	}
+	// Reset the block sizes of the node to adjust them
+	// with the new values of the truncated children.
+	ndata.RemoveAllBlockSizes()
 	for i, lnk := range nd.Links() {
 		child, err := lnk.GetNode(ctx, ds)
 		if err != nil {
@@ -558,7 +564,7 @@ func dagTruncate(ctx context.Context, n ipld.Node, size uint64, ds ipld.DAGServi
 		ndata.AddBlockSize(childsize)
 	}
 
-	err := ds.Add(ctx, modified)
+	err = ds.Add(ctx, modified)
 	if err != nil {
 		return nil, err
 	}
@@ -573,7 +579,7 @@ func dagTruncate(ctx context.Context, n ipld.Node, size uint64, ds ipld.DAGServi
 	if err != nil {
 		return nil, err
 	}
-
+	// Save the new block sizes to the original node.
 	nd.SetData(d)
 
 	// invalidate cache and recompute serialized data

unixfs/mod/dagmodifier_test.go

@@ -406,6 +406,44 @@ func testDagTruncate(t *testing.T, opts testu.NodeOpts) {
 	}
 }
 
+// TestDagTruncateSameSize tests that a DAG truncated
+// to the same size (i.e., doing nothing) doesn't modify
+// the DAG (its hash).
+func TestDagTruncateSameSize(t *testing.T) {
+	runAllSubtests(t, testDagTruncateSameSize)
+}
+func testDagTruncateSameSize(t *testing.T, opts testu.NodeOpts) {
+	dserv := testu.GetDAGServ()
+	_, n := testu.GetRandomNode(t, dserv, 50000, opts)
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	dagmod, err := NewDagModifier(ctx, n, dserv, testu.SizeSplitterGen(512))
+	if err != nil {
+		t.Fatal(err)
+	}
+	// Copied from `TestDagTruncate`.
+
+	size, err := dagmod.Size()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = dagmod.Truncate(size)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	modifiedNode, err := dagmod.GetNode()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if modifiedNode.Cid().Equals(n.Cid()) == false {
+		t.Fatal("the node has been modified!")
+	}
+}
+
 func TestSparseWrite(t *testing.T) {
 	runAllSubtests(t, testSparseWrite)
 }

unixfs/unixfs.go

@@ -201,6 +201,12 @@ func (n *FSNode) BlockSize(i int) uint64 {
 	return n.format.Blocksizes[i]
 }
 
+// RemoveAllBlockSizes removes all the child block sizes of this node.
+func (n *FSNode) RemoveAllBlockSizes() {
+	n.format.Blocksizes = []uint64{}
+	n.format.Filesize = proto.Uint64(uint64(len(n.Data())))
+}
+
 // GetBytes marshals this node as a protobuf message.
 func (n *FSNode) GetBytes() ([]byte, error) {
 	return proto.Marshal(&n.format)