Merge pull request #299 from lazyledger/hlib/empty-block-retrieve

p2p/ipld/nmt_wrapper.go

@@ -1,12 +1,14 @@
 package ipld
 
 import (
+	"bytes"
 	"crypto/sha256"
 
-	"github.com/lazyledger/lazyledger-core/types"
 	"github.com/lazyledger/nmt"
 	"github.com/lazyledger/nmt/namespace"
 	"github.com/lazyledger/rsmt2d"
+
+	"github.com/lazyledger/lazyledger-core/types"
 )
 
 // Fulfills the rsmt2d.Tree interface and rsmt2d.TreeConstructorFn function
@@ -50,12 +52,16 @@ func (w *ErasuredNamespacedMerkleTree) Push(data []byte, idx rsmt2d.SquareIndex)
 		panic("pushed past predetermined square size")
 	}
 
-	// use the parity namespace if the cell is not in Q0 of the extended
-	// datasquare
+	// use the parity namespace if the cell is not in Q0 of the extended datasquare
+	// if the cell is empty it means we got an empty block so we need to use TailPaddingNamespaceID
 	if idx.Axis+1 > uint(w.squareSize) || idx.Cell+1 > uint(w.squareSize) {
 		copy(nsID, types.ParitySharesNamespaceID)
 	} else {
-		copy(nsID, data[:types.NamespaceSize])
+		if bytes.Equal(data[:types.NamespaceSize], nsID) {
+			copy(nsID, types.TailPaddingNamespaceID)
+		} else {
+			copy(nsID, data[:types.NamespaceSize])
+		}
 	}
 	nidAndData := append(append(make([]byte, 0, types.NamespaceSize+len(data)), nsID...), data...)
 	// push to the underlying tree

p2p/ipld/read_test.go

@@ -229,6 +229,7 @@ func TestRetrieveBlockData(t *testing.T) {
 	adjustedMsgSize := types.MsgShareSize - 2
 
 	tests := []test{
+		{"Empty block", 1, false, ""},
 		{"4 KB block", 4, false, ""},
 		{"16 KB block", 8, false, ""},
 		{"16 KB block timeout expected", 8, true, "timeout"},
@@ -391,6 +392,9 @@ func rootsToDigests(roots [][]byte) []namespace.IntervalDigest {
 
 func generateRandomBlockData(msgCount, msgSize int) types.Data {
 	var out types.Data
+	if msgCount == 1 {
+		return out
+	}
 	out.Messages = generateRandomMessages(msgCount-1, msgSize)
 	out.Txs = generateRandomContiguousShares(1)
 	return out