go/tendermint/staking/state.SlashEscrow: return slashed amount

go/consensus/tendermint/apps/staking/slashing_test.go

@@ -88,10 +88,10 @@ func TestOnEvidenceConsensusEquivocation(t *testing.T) {
 	})
 	require.NoError(err, "SetConsensusParameters")
 
-	// Should fail as the validator has no stake (which is an invariant violation as a validator
-	// needs to have some stake).
+	// Should not fail if the validator has no stake (which is in any case an
+	// invariant violation as a validator needs to have some stake).
 	err = onEvidenceConsensusEquivocation(ctx, validatorAddress, 1, now, 1)
-	require.Error(err, "should fail when validator has no stake")
+	require.NoError(err, "should fail when validator has no stake")
 
 	// Computes entity's staking address.
 	addr := staking.NewAddress(ent.ID)

go/consensus/tendermint/apps/staking/state/state.go

@@ -606,6 +606,10 @@ func (s *MutableState) SetGovernanceDeposits(ctx context.Context, q *quantity.Qu
 }
 
 func slashPool(dst *quantity.Quantity, p *staking.SharePool, amount, total *quantity.Quantity) error {
+	if total.IsZero() {
+		// Nothing to slash.
+		return nil
+	}
 	// slashAmount = amount * p.Balance / total
 	slashAmount := p.Balance.Clone()
 	if err := slashAmount.Mul(amount); err != nil {
@@ -624,55 +628,55 @@ func slashPool(dst *quantity.Quantity, p *staking.SharePool, amount, total *quan
 
 // SlashEscrow slashes the escrow balance and the escrow-but-undergoing-debonding
 // balance of the account, transferring it to the global common pool, returning
-// true iff the amount actually slashed is > 0.
+// the amount actually slashed.
 //
 // WARNING: This is an internal routine to be used to implement staking policy,
 // and MUST NOT be exposed outside of backend implementations.
 func (s *MutableState) SlashEscrow(
 	ctx *abciAPI.Context,
 	fromAddr staking.Address,
 	amount *quantity.Quantity,
-) (bool, error) {
+) (*quantity.Quantity, error) {
+	var slashed quantity.Quantity
+
 	commonPool, err := s.CommonPool(ctx)
 	if err != nil {
-		return false, fmt.Errorf("tendermint/staking: failed to query common pool for slash: %w", err)
+		return nil, fmt.Errorf("tendermint/staking: failed to query common pool for slash: %w", err)
 	}
 
 	from, err := s.Account(ctx, fromAddr)
 	if err != nil {
-		return false, fmt.Errorf("tendermint/staking: failed to query account %s: %w", fromAddr, err)
+		return nil, fmt.Errorf("tendermint/staking: failed to query account %s: %w", fromAddr, err)
 	}
 
 	// Compute the amount we need to slash each pool. The amount is split
 	// between the pools based on relative total balance.
 	total := from.Escrow.Active.Balance.Clone()
 	if err = total.Add(&from.Escrow.Debonding.Balance); err != nil {
-		return false, fmt.Errorf("tendermint/staking: compute total balance: %w", err)
+		return nil, fmt.Errorf("tendermint/staking: account total balance: %w", err)
+	}
+	// Nothing to slash.
+	if total.IsZero() {
+		return &slashed, nil
 	}
 
-	var slashed quantity.Quantity
 	if err = slashPool(&slashed, &from.Escrow.Active, amount, total); err != nil {
-		return false, fmt.Errorf("tendermint/staking: failed slashing active escrow: %w", err)
+		return nil, fmt.Errorf("tendermint/staking: failed slashing active escrow: %w", err)
 	}
 	if err = slashPool(&slashed, &from.Escrow.Debonding, amount, total); err != nil {
-		return false, fmt.Errorf("tendermint/staking: failed slashing debonding escrow: %w", err)
+		return nil, fmt.Errorf("tendermint/staking: failed slashing debonding escrow: %w", err)
 	}
-
-	if slashed.IsZero() {
-		return false, nil
-	}
-
 	totalSlashed := slashed.Clone()
 
 	if err = quantity.Move(commonPool, &slashed, totalSlashed); err != nil {
-		return false, fmt.Errorf("tendermint/staking: failed moving stake to common pool: %w", err)
+		return nil, fmt.Errorf("tendermint/staking: failed moving stake to common pool: %w", err)
 	}
 
 	if err = s.SetCommonPool(ctx, commonPool); err != nil {
-		return false, fmt.Errorf("tendermint/staking: failed to set common pool: %w", err)
+		return nil, fmt.Errorf("tendermint/staking: failed to set common pool: %w", err)
 	}
 	if err = s.SetAccount(ctx, fromAddr, from); err != nil {
-		return false, fmt.Errorf("tendermint/staking: failed to set account. %w", err)
+		return nil, fmt.Errorf("tendermint/staking: failed to set account: %w", err)
 	}
 
 	if !ctx.IsCheckOnly() {
@@ -683,7 +687,7 @@ func (s *MutableState) SlashEscrow(
 		ctx.EmitEvent(api.NewEventBuilder(AppName).Attribute(KeyTakeEscrow, ev))
 	}
 
-	return true, nil
+	return totalSlashed, nil
 }
 
 // TransferFromCommon transfers up to the amount from the global common pool

go/consensus/tendermint/apps/staking/state/state_test.go

@@ -251,9 +251,9 @@ func TestRewardAndSlash(t *testing.T) {
 	require.NoError(err, "Account")
 	require.Equal(mustInitQuantity(t, 300), escrowAccount.Escrow.Active.Balance, "reward late epoch - escrow active escrow")
 
-	slashedNonzero, err := s.SlashEscrow(ctx, escrowAddr, mustInitQuantityP(t, 40))
+	slashed, err := s.SlashEscrow(ctx, escrowAddr, mustInitQuantityP(t, 40))
 	require.NoError(err, "slash escrow")
-	require.True(slashedNonzero, "slashed nonzero")
+	require.False(slashed.IsZero(), "slashed nonzero")
 
 	// Loss of 40 base units.
 	delegatorAccount, err = s.Account(ctx, delegatorAddr)