R4R: Block redelegations to the same validator

PENDING.md

@@ -37,6 +37,7 @@ IMPROVEMENTS
 
 * SDK
  - #2573 [x/distribution] add accum invariance
+ - #2610 [x/stake] Block redelegation to and from the same validator
 
 * Tendermint
 

x/stake/keeper/delegation.go

@@ -541,6 +541,10 @@ func (k Keeper) CompleteUnbonding(ctx sdk.Context, delAddr sdk.AccAddress, valAd
 func (k Keeper) BeginRedelegation(ctx sdk.Context, delAddr sdk.AccAddress,
 	valSrcAddr, valDstAddr sdk.ValAddress, sharesAmount sdk.Dec) (types.Redelegation, sdk.Error) {
 
+	if bytes.Equal(valSrcAddr, valDstAddr) {
+		return types.Redelegation{}, types.ErrSelfRedelegation(k.Codespace())
+	}
+
 	// check if there is already a redelgation in progress from src to dst
 	// TODO quick fix, instead we should use an index, see https://github.com/cosmos/cosmos-sdk/issues/1402
 	_, found := k.GetRedelegation(ctx, delAddr, valSrcAddr, valDstAddr)

x/stake/keeper/delegation_test.go

@@ -581,6 +581,32 @@ func TestRedelegation(t *testing.T) {
 	require.Equal(t, 0, len(redelegations))
 }
 
+func TestRedelegateToSameValidator(t *testing.T) {
+
+	ctx, _, keeper := CreateTestInput(t, false, 0)
+	pool := keeper.GetPool(ctx)
+	pool.LooseTokens = sdk.NewDec(30)
+
+	// create a validator with a self-delegation
+	validator := types.NewValidator(addrVals[0], PKs[0], types.Description{})
+	validator, pool, issuedShares := validator.AddTokensFromDel(pool, sdk.NewInt(10))
+	require.Equal(t, int64(10), issuedShares.RoundInt64())
+	keeper.SetPool(ctx, pool)
+	validator = TestingUpdateValidator(keeper, ctx, validator)
+	pool = keeper.GetPool(ctx)
+	val0AccAddr := sdk.AccAddress(addrVals[0].Bytes())
+	selfDelegation := types.Delegation{
+		DelegatorAddr: val0AccAddr,
+		ValidatorAddr: addrVals[0],
+		Shares:        issuedShares,
+	}
+	keeper.SetDelegation(ctx, selfDelegation)
+
+	_, err := keeper.BeginRedelegation(ctx, val0AccAddr, addrVals[0], addrVals[0], sdk.NewDec(5))
+	require.Error(t, err)
+
+}
+
 func TestRedelegateSelfDelegation(t *testing.T) {
 
 	ctx, _, keeper := CreateTestInput(t, false, 0)

x/stake/types/errors.go

@@ -155,6 +155,10 @@ func ErrNoRedelegation(codespace sdk.CodespaceType) sdk.Error {
 	return sdk.NewError(codespace, CodeInvalidDelegation, "no redelegation found")
 }
 
+func ErrSelfRedelegation(codespace sdk.CodespaceType) sdk.Error {
+	return sdk.NewError(codespace, CodeInvalidDelegation, "cannot redelegate to the same validator")
+}
+
 func ErrBadRedelegationDst(codespace sdk.CodespaceType) sdk.Error {
 	return sdk.NewError(codespace, CodeInvalidDelegation, "redelegation validator not found")
 }