Merge pull request #345 from PeggyJV/bolten/reject-empty-batches

module/x/gravity/keeper/batch.go

@@ -36,6 +36,11 @@ func (k Keeper) BuildBatchTx(ctx sdk.Context, contractAddress common.Address, ma
 		return len(selectedStes) == maxElements
 	})
 
+	// do not create batches that would contain no transactions, even if they are requested
+	if len(selectedStes) == 0 {
+		return nil
+	}
+
 	batch := &types.BatchTx{
 		BatchNonce:    k.incrementLastOutgoingBatchNonce(ctx),
 		Timeout:       k.getBatchTimeoutHeight(ctx),

module/x/gravity/keeper/batch_test.go

@@ -354,3 +354,29 @@ func TestPoolTxRefund(t *testing.T) {
 	balances := input.BankKeeper.GetAllBalances(ctx, mySender)
 	require.Equal(t, sdk.NewInt(104), balances.AmountOf(myDenom))
 }
+
+func TestEmptyBatch(t *testing.T) {
+	input := CreateTestEnv(t)
+	ctx := input.Context
+
+	var (
+		now                 = time.Now().UTC()
+		mySender, _         = sdk.AccAddressFromBech32("cosmos1ahx7f8wyertuus9r20284ej0asrs085case3kn")
+		myTokenContractAddr = common.HexToAddress("0x429881672B9AE42b8EbA0E26cD9C73711b891Ca5") // Pickle
+		allVouchers         = sdk.NewCoins(
+			types.NewERC20Token(99999, myTokenContractAddr.Hex()).GravityCoin(),
+		)
+	)
+
+	// mint some voucher first
+	require.NoError(t, input.BankKeeper.MintCoins(ctx, types.ModuleName, allVouchers))
+	// set senders balance
+	input.AccountKeeper.NewAccountWithAddress(ctx, mySender)
+	require.NoError(t, fundAccount(ctx, input.BankKeeper, mySender, allVouchers))
+
+	// no transactions should be included in this batch
+	ctx = ctx.WithBlockTime(now)
+	batchTx := input.GravityKeeper.BuildBatchTx(ctx, myTokenContractAddr, 2)
+
+	require.Nil(t, batchTx)
+}

module/x/gravity/keeper/msg_server.go

@@ -250,6 +250,9 @@ func (k msgServer) RequestBatchTx(c context.Context, msg *types.MsgRequestBatchT
 	}
 
 	batchID := k.BuildBatchTx(ctx, tokenContract, BatchTxSize)
+	if batchID == nil {
+		return nil, fmt.Errorf("no suitable batch to create")
+	}
 
 	ctx.EventManager().EmitEvent(
 		sdk.NewEvent(

module/x/gravity/keeper/msg_server_test.go

@@ -210,14 +210,85 @@ func TestMsgServer_CancelSendToEthereum(t *testing.T) {
 }
 
 func TestMsgServer_RequestBatchTx(t *testing.T) {
+	ethPrivKey, err := ethCrypto.GenerateKey()
+	require.NoError(t, err)
+
+	var (
+		env = CreateTestEnv(t)
+		ctx = env.Context
+		gk  = env.GravityKeeper
+
+		orcAddr1, _ = sdk.AccAddressFromBech32("cosmos1dg55rtevlfxh46w88yjpdd08sqhh5cc3xhkcej")
+		valAddr1    = sdk.ValAddress(orcAddr1)
+		ethAddr1    = crypto.PubkeyToAddress(ethPrivKey.PublicKey)
+
+		orcAddr2, _ = sdk.AccAddressFromBech32("cosmos164knshrzuuurf05qxf3q5ewpfnwzl4gj4m4dfy")
+		valAddr2    = sdk.ValAddress(orcAddr2)
+
+		orcAddr3, _ = sdk.AccAddressFromBech32("cosmos193fw83ynn76328pty4yl7473vg9x86alq2cft7")
+		valAddr3    = sdk.ValAddress(orcAddr3)
+
+		testDenom = "stake"
+
+		balance = sdk.Coin{
+			Denom:  testDenom,
+			Amount: sdk.NewInt(10000),
+		}
+		amount = sdk.Coin{
+			Denom:  testDenom,
+			Amount: sdk.NewInt(1000),
+		}
+		fee = sdk.Coin{
+			Denom:  testDenom,
+			Amount: sdk.NewInt(10),
+		}
+	)
+
+	{ // setup for getSignerValidator
+		gk.StakingKeeper = NewStakingKeeperMock(valAddr1, valAddr2, valAddr3)
+		gk.SetOrchestratorValidatorAddress(ctx, valAddr1, orcAddr1)
+	}
+
+	{ // add balance to bank
+		err = env.AddBalanceToBank(ctx, orcAddr1, sdk.Coins{balance})
+		require.NoError(t, err)
+	}
+
+	// create denom in keeper
+	gk.setCosmosOriginatedDenomToERC20(ctx, testDenom, "testcontractstring")
+
+	// setup for GetValidatorEthereumAddress
+	gk.setValidatorEthereumAddress(ctx, valAddr1, ethAddr1)
+
+	msgServer := NewMsgServerImpl(gk)
+
+	msg := &types.MsgSendToEthereum{
+		Sender:            orcAddr1.String(),
+		EthereumRecipient: ethAddr1.String(),
+		Amount:            amount,
+		BridgeFee:         fee,
+	}
+
+	_, err = msgServer.SendToEthereum(sdk.WrapSDKContext(ctx), msg)
+	require.NoError(t, err)
+
+	requestMsg := &types.MsgRequestBatchTx{
+		Signer: orcAddr1.String(),
+		Denom:  testDenom,
+	}
+
+	_, err = msgServer.RequestBatchTx(sdk.WrapSDKContext(ctx), requestMsg)
+	require.NoError(t, err)
+}
+
+func TestMsgServer_RequestEmptyBatchTx(t *testing.T) {
 	var (
 		env = CreateTestEnv(t)
 		ctx = env.Context
 		gk  = env.GravityKeeper
 
 		orcAddr1, _ = sdk.AccAddressFromBech32("cosmos1dg55rtevlfxh46w88yjpdd08sqhh5cc3xhkcej")
 		valAddr1    = sdk.ValAddress(orcAddr1)
-		//ethAddr1    = crypto.PubkeyToAddress(ethPrivKey.PublicKey)
 
 		orcAddr2, _ = sdk.AccAddressFromBech32("cosmos164knshrzuuurf05qxf3q5ewpfnwzl4gj4m4dfy")
 		valAddr2    = sdk.ValAddress(orcAddr2)
@@ -244,7 +315,8 @@ func TestMsgServer_RequestBatchTx(t *testing.T) {
 	}
 
 	_, err := msgServer.RequestBatchTx(sdk.WrapSDKContext(ctx), msg)
-	require.NoError(t, err)
+
+	require.Error(t, err)
 }
 
 func TestMsgServer_SubmitEthereumEvent(t *testing.T) {