add error checking for nil keys

Checks in:
- blockstore
- blockservice
- dagservice
- bitswap

Do not anger the pokemans #2715

License: MIT
Signed-off-by: Juan Benet <juan@benet.ai>

bitswap.go

@@ -155,6 +155,9 @@ type blockRequest struct {
 // GetBlock attempts to retrieve a particular block from peers within the
 // deadline enforced by the context.
 func (bs *Bitswap) GetBlock(parent context.Context, k key.Key) (blocks.Block, error) {
+	if k == "" {
+		return nil, blockstore.ErrNotFound
+	}
 
 	// Any async work initiated by this function must end when this function
 	// returns. To ensure this, derive a new context. Note that it is okay to

bitswap_test.go

@@ -11,6 +11,7 @@ import (
 	context "gx/ipfs/QmZy2y8t9zQH2a1b8q2ZSLKp17ATuJoCNxxyMFG5qFExpt/go-net/context"
 
 	blocks "github.com/ipfs/go-ipfs/blocks"
+	blockstore "github.com/ipfs/go-ipfs/blocks/blockstore"
 	blocksutil "github.com/ipfs/go-ipfs/blocks/blocksutil"
 	key "github.com/ipfs/go-ipfs/blocks/key"
 	tn "github.com/ipfs/go-ipfs/exchange/bitswap/testnet"
@@ -278,6 +279,18 @@ func TestSendToWantingPeer(t *testing.T) {
 
 }
 
+func TestEmptyKey(t *testing.T) {
+	net := tn.VirtualNetwork(mockrouting.NewServer(), delay.Fixed(kNetworkDelay))
+	sg := NewTestSessionGenerator(net)
+	defer sg.Close()
+	bs := sg.Instances(1)[0].Exchange
+
+	_, err := bs.GetBlock(context.Background(), key.Key(""))
+	if err != blockstore.ErrNotFound {
+		t.Error("empty str key should return ErrNotFound")
+	}
+}
+
 func TestBasicBitswap(t *testing.T) {
 	net := tn.VirtualNetwork(mockrouting.NewServer(), delay.Fixed(kNetworkDelay))
 	sg := NewTestSessionGenerator(net)