Create a raw node instead of a file node when there is no content.

importer/balanced/builder.go

@@ -51,7 +51,12 @@ func Layout(db *h.DagBuilderHelper) (ipld.Node, error) {
 
 	}
 	if root == nil {
-		root = db.NewUnixfsNode()
+		// this should only happen with an empty node, so return a leaf
+		var err error
+		root, err = db.NewLeaf(nil)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	out, err := db.Add(root)

importer/helpers/dagbuilder.go

@@ -122,6 +122,41 @@ func (db *DagBuilderHelper) NewUnixfsNode() *UnixfsNode {
 	return n
 }
 
+// NewLeaf creates a leaf node filled with data.  If rawLeaves is
+// defined than a raw leaf will be returned.  Otherwise, if data is
+// nil the type field will be TRaw (for backwards compatibility), if
+// data is defined (but possibly empty) the type field will be TRaw.
+func (db *DagBuilderHelper) NewLeaf(data []byte) (*UnixfsNode, error) {
+	if len(data) > BlockSizeLimit {
+		return nil, ErrSizeLimitExceeded
+	}
+
+	if db.rawLeaves {
+		if db.prefix == nil {
+			return &UnixfsNode{
+				rawnode: dag.NewRawNode(data),
+				raw:     true,
+			}, nil
+		}
+		rawnode, err := dag.NewRawNodeWPrefix(data, *db.prefix)
+		if err != nil {
+			return nil, err
+		}
+		return &UnixfsNode{
+			rawnode: rawnode,
+			raw:     true,
+		}, nil
+	}
+
+	if data == nil {
+		return db.NewUnixfsNode(), nil
+	}
+
+	blk := db.newUnixfsBlock()
+	blk.SetData(data)
+	return blk, nil
+}
+
 // newUnixfsBlock creates a new Unixfs node to represent a raw data block
 func (db *DagBuilderHelper) newUnixfsBlock() *UnixfsNode {
 	n := &UnixfsNode{
@@ -164,30 +199,7 @@ func (db *DagBuilderHelper) GetNextDataNode() (*UnixfsNode, error) {
 		return nil, nil
 	}
 
-	if len(data) > BlockSizeLimit {
-		return nil, ErrSizeLimitExceeded
-	}
-
-	if db.rawLeaves {
-		if db.prefix == nil {
-			return &UnixfsNode{
-				rawnode: dag.NewRawNode(data),
-				raw:     true,
-			}, nil
-		}
-		rawnode, err := dag.NewRawNodeWPrefix(data, *db.prefix)
-		if err != nil {
-			return nil, err
-		}
-		return &UnixfsNode{
-			rawnode: rawnode,
-			raw:     true,
-		}, nil
-	}
-
-	blk := db.newUnixfsBlock()
-	blk.SetData(data)
-	return blk, nil
+	return db.NewLeaf(data)
 }
 
 // SetPosInfo sets the offset information of a node using the fullpath and stat

test/sharness/t0040-add-and-cat.sh

@@ -166,6 +166,24 @@ test_add_cat_file() {
     echo "added $HASH .hello.txt" >expected &&
     test_cmp expected actual
   '
+
+  test_expect_success "add zero length file" '
+    touch zero-length-file &&
+    ZEROHASH=$(ipfs add -q zero-length-file) &&
+    echo $ZEROHASH
+  '
+
+  test_expect_success "zero length file has correct hash" '
+    test "$ZEROHASH" = QmbFMke1KXqnYyBBWxB74N4c5SBnJMVAiMNRcGu6x1AwQH
+  '
+
+  test_expect_success "cat zero length file" '
+    ipfs cat $ZEROHASH > zero-length-file_out
+  '
+
+  test_expect_success "make sure it looks good" '
+    test_cmp zero-length-file zero-length-file_out
+  '
 }
 
 test_add_cat_5MB() {
@@ -221,6 +239,24 @@ test_add_cat_raw() {
   test_expect_success "make sure it looks good" '
     test_cmp afile afile_out
   '
+
+  test_expect_success "add zero length file with raw-leaves" '
+    touch zero-length-file &&
+    ZEROHASH=$(ipfs add -q --raw-leaves zero-length-file) &&
+    echo $ZEROHASH
+  '
+
+  test_expect_success "zero length file has correct hash" '
+    test "$ZEROHASH" = zb2rhmy65F3REf8SZp7De11gxtECBGgUKaLdiDj7MCGCHxbDW
+  '
+
+  test_expect_success "cat zero length file" '
+    ipfs cat $ZEROHASH > zero-length-file_out
+  '
+
+  test_expect_success "make sure it looks good" '
+    test_cmp zero-length-file zero-length-file_out
+  '
 }
 
 test_add_cat_expensive() {