CreateValidator self delegation must be at least one consensus power

CHANGELOG.md

@@ -75,6 +75,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### Improvements
 
+* (x/staking) [\#8909](https://github.com/cosmos/cosmos-sdk/pull/8909) Require self delegation in `MsgCreateValidator` to be at least one consensus power. 
 * (x/bank) [\#8614](https://github.com/cosmos/cosmos-sdk/issues/8614) Add `Name` and `Symbol` fields to denom metadata
 * (x/auth) [\#8522](https://github.com/cosmos/cosmos-sdk/pull/8522) Allow to query all stored accounts
 * (crypto/types) [\#8600](https://github.com/cosmos/cosmos-sdk/pull/8600) `CompactBitArray`: optimize the `NumTrueBitsBefore` method and add an `Equal` method.

x/staking/types/msg.go

@@ -140,6 +140,11 @@ func (msg MsgCreateValidator) ValidateBasic() error {
 		return ErrMinSelfDelegationInvalid
 	}
 
+	// ensure delegation is at least one consensus power
+	if sdk.TokensToConsensusPower(msg.Value.Amount) <= 0 {
+		return sdkerrors.Wrapf(ErrBadDelegationAmount, "self delegation amount (%s) must be at least one consensus power (%s)", msg.Value.Amount, sdk.PowerReduction)
+	}
+
 	if msg.Value.Amount.LT(msg.MinSelfDelegation) {
 		return ErrSelfDelegationBelowMinimum
 	}

x/staking/types/msg_test.go

@@ -15,7 +15,7 @@ import (
 )
 
 var (
-	coinPos  = sdk.NewInt64Coin(sdk.DefaultBondDenom, 1000)
+	coinPos  = sdk.NewInt64Coin(sdk.DefaultBondDenom, sdk.PowerReduction.Int64())
 	coinZero = sdk.NewInt64Coin(sdk.DefaultBondDenom, 0)
 )
 
@@ -75,6 +75,7 @@ func TestMsgCreateValidator(t *testing.T) {
 		{"zero min self delegation", "a", "b", "c", "d", "e", commission1, sdk.ZeroInt(), valAddr1, pk1, coinPos, false},
 		{"negative min self delegation", "a", "b", "c", "d", "e", commission1, sdk.NewInt(-1), valAddr1, pk1, coinPos, false},
 		{"delegation less than min self delegation", "a", "b", "c", "d", "e", commission1, coinPos.Amount.Add(sdk.OneInt()), valAddr1, pk1, coinPos, false},
+		{"delegation less than one consensus power", "a", "b", "c", "d", "e", commission1, sdk.OneInt(), valAddr1, pk1, sdk.NewInt64Coin(sdk.DefaultBondDenom, 1000), false},
 	}
 
 	for _, tc := range tests {