[Hotfix] treasury empty epoch data (#445)

* prevent division by zero, even though no epoch data is stored

* add test case for empty epoch data

x/treasury/abci_test.go

@@ -64,3 +64,43 @@ func TestUpdate(t *testing.T) {
 	newRewardWeight := input.TreasuryKeeper.GetRewardWeight(input.Ctx)
 	require.Equal(t, rewardWeight.Add(input.TreasuryKeeper.RewardPolicy(input.Ctx).ChangeRateMax), newRewardWeight)
 }
+
+func TestEmptyIndicator(t *testing.T) {
+	input := keeper.CreateTestInput(t)
+
+	windowProbation := input.TreasuryKeeper.WindowProbation(input.Ctx)
+
+	// Set total staked luna to prevent divide by zero error when computing TRL
+	bondedModuleAcc := input.SupplyKeeper.GetModuleAccount(input.Ctx, stakingtypes.BondedPoolName)
+	err := bondedModuleAcc.SetCoins(sdk.NewCoins(sdk.NewInt64Coin(core.MicroLunaDenom, 100000000000)))
+	require.NoError(t, err)
+	input.SupplyKeeper.SetModuleAccount(input.Ctx, bondedModuleAcc)
+
+	targetEpoch := windowProbation + 1
+	for epoch := int64(0); epoch < targetEpoch; epoch++ {
+		// skip last epoch end blocker
+		// to make indicators empty
+		if epoch == targetEpoch-1 {
+			continue
+		}
+
+		input.Ctx = input.Ctx.WithBlockHeight(core.BlocksPerWeek*epoch - 1)
+		EndBlocker(input.Ctx, input.TreasuryKeeper)
+	}
+
+	// Must result in the same output as normal zero tax & mining rewards
+	// load old tax rate & reward weight
+	taxRate := input.TreasuryKeeper.GetTaxRate(input.Ctx)
+	rewardWeight := input.TreasuryKeeper.GetRewardWeight(input.Ctx)
+
+	input.Ctx = input.Ctx.WithBlockHeight(core.BlocksPerWeek*targetEpoch - 1)
+	EndBlocker(input.Ctx, input.TreasuryKeeper)
+
+	// zero tax proceeds will increase tax rate with change max amount
+	newTaxRate := input.TreasuryKeeper.GetTaxRate(input.Ctx)
+	require.Equal(t, taxRate.Add(input.TreasuryKeeper.TaxPolicy(input.Ctx).ChangeRateMax), newTaxRate)
+
+	// zero mining rewards will increase reward weight with change max amount
+	newRewardWeight := input.TreasuryKeeper.GetRewardWeight(input.Ctx)
+	require.Equal(t, rewardWeight.Add(input.TreasuryKeeper.RewardPolicy(input.Ctx).ChangeRateMax), newRewardWeight)
+}

x/treasury/internal/keeper/keeper.go

@@ -314,7 +314,7 @@ func (k Keeper) GetTSL(ctx sdk.Context, epoch int64) (res sdk.Int) {
 	bz := store.Get(types.GetTSLKey(epoch))
 
 	if bz == nil {
-		res = sdk.ZeroInt()
+		res = sdk.OneInt()
 	} else {
 		k.cdc.MustUnmarshalBinaryLengthPrefixed(bz, &res)
 	}

x/treasury/internal/keeper/keeper_test.go

@@ -157,7 +157,7 @@ func TestIndicatorGetterSetter(t *testing.T) {
 	for e := int64(0); e < 10; e++ {
 		require.Equal(t, sdk.ZeroDec(), input.TreasuryKeeper.GetTR(input.Ctx, e))
 		require.Equal(t, sdk.ZeroDec(), input.TreasuryKeeper.GetSR(input.Ctx, e))
-		require.Equal(t, sdk.ZeroInt(), input.TreasuryKeeper.GetTSL(input.Ctx, e))
+		require.Equal(t, sdk.OneInt(), input.TreasuryKeeper.GetTSL(input.Ctx, e))
 	}
 }