Merge pull request #574 from okp4/feat/mint-inflation-bounds

feat(mint): add optional inflation bounds params

Author: amimart

docs/proto/mint.md

@@ -74,6 +74,8 @@ Params defines the parameters for the mint module.
 | `mint_denom` | [string](#string) |  | Denomination of the coin to be minted. |
 | `inflation_coef` | [string](#string) |  | Annual inflation coefficient, influencing the inflation rate based on the bonded ratio. Values range from 0 to 1, with higher values indicating higher inflation. |
 | `blocks_per_year` | [uint64](#uint64) |  | Estimated number of blocks per year. |
+| `inflation_max` | [string](#string) |  | Maximum annual inflation rate. |
+| `inflation_min` | [string](#string) |  | Minimum annual inflation rate. |
 
  [//]: # (end messages)
 

proto/mint/v1beta1/mint.proto

@@ -37,6 +37,21 @@ message Params {
     (gogoproto.customtype) = "cosmossdk.io/math.LegacyDec",
     (gogoproto.nullable) = false
   ];
+
   // Estimated number of blocks per year.
   uint64 blocks_per_year = 3;
+
+  // Maximum annual inflation rate.
+  string inflation_max = 4 [
+    (cosmos_proto.scalar) = "cosmos.Dec",
+    (gogoproto.customtype) = "cosmossdk.io/math.LegacyDec",
+    (gogoproto.nullable) = true
+  ];
+
+  // Minimum annual inflation rate.
+  string inflation_min = 5 [
+    (cosmos_proto.scalar) = "cosmos.Dec",
+    (gogoproto.customtype) = "cosmossdk.io/math.LegacyDec",
+    (gogoproto.nullable) = true
+  ];
 }

x/mint/abci.go

@@ -28,7 +28,13 @@ func BeginBlocker(ctx context.Context, k keeper.Keeper) error {
 		return err
 	}
 
-	minter, err := types.NewMinterWithInflationCoef(params.InflationCoef, bondedRatio, totalSupply)
+	minter, err := types.NewMinterWithInflationCoef(
+		params.InflationCoef,
+		bondedRatio,
+		params.InflationMin,
+		params.InflationMax,
+		totalSupply,
+	)
 	if err != nil {
 		panic(err)
 	}
@@ -66,6 +72,5 @@ func BeginBlocker(ctx context.Context, k keeper.Keeper) error {
 			sdk.NewAttribute(sdk.AttributeKeyAmount, mintedCoin.Amount.String()),
 		),
 	)
-
 	return nil
 }

x/mint/client/cli/query_test.go

@@ -46,14 +46,16 @@ func TestGetCmdQueryParams(t *testing.T) {
 			"json output",
 			[]string{fmt.Sprintf("--%s=1", flags.FlagHeight), fmt.Sprintf("--%s=json", flags.FlagOutput)},
 			`[--height=1 --output=json]`,
-			`{"mint_denom":"","inflation_coef":"0","blocks_per_year":"0"}`,
+			`{"mint_denom":"","inflation_coef":"0","blocks_per_year":"0","inflation_max":null,"inflation_min":null}`,
 		},
 		{
 			"text output",
 			[]string{fmt.Sprintf("--%s=1", flags.FlagHeight), fmt.Sprintf("--%s=text", flags.FlagOutput)},
 			`[--height=1 --output=text]`,
 			`blocks_per_year: "0"
 inflation_coef: "0"
+inflation_max: null
+inflation_min: null
 mint_denom: ""`,
 		},
 	}

x/mint/keeper/msg_server_test.go

@@ -9,6 +9,11 @@ import (
 )
 
 func (s *IntegrationTestSuite) TestUpdateParams() {
+	validInfMin := math.LegacyNewDecWithPrec(3, 2)
+	validInfMax := math.LegacyNewDecWithPrec(20, 2)
+	invalidInfMin := math.LegacyNewDecWithPrec(-3, 2)
+	invalidInfMax := math.LegacyNewDecWithPrec(-20, 2)
+
 	testCases := []struct {
 		name      string
 		request   *types.MsgUpdateParams
@@ -34,12 +39,70 @@ func (s *IntegrationTestSuite) TestUpdateParams() {
 			expectErr: true,
 		},
 		{
-			name: "set full valid params",
+			name: "set invalid params for inflation max (negative value)",
+			request: &types.MsgUpdateParams{
+				Authority: s.mintKeeper.GetAuthority(),
+				Params: types.Params{
+					MintDenom:     sdk.DefaultBondDenom,
+					InflationCoef: math.LegacyNewDecWithPrec(73, 2),
+					InflationMax:  &invalidInfMax,
+					InflationMin:  nil,
+					BlocksPerYear: uint64(60 * 60 * 8766 / 5),
+				},
+			},
+			expectErr: true,
+		},
+		{
+			name: "set invalid params for inflation min (negative value)",
+			request: &types.MsgUpdateParams{
+				Authority: s.mintKeeper.GetAuthority(),
+				Params: types.Params{
+					MintDenom:     sdk.DefaultBondDenom,
+					InflationCoef: math.LegacyNewDecWithPrec(73, 2),
+					InflationMax:  nil,
+					InflationMin:  &invalidInfMin,
+					BlocksPerYear: uint64(60 * 60 * 8766 / 5),
+				},
+			},
+			expectErr: true,
+		},
+		{
+			name: "set invalid params for inflation min & max (min > max)",
+			request: &types.MsgUpdateParams{
+				Authority: s.mintKeeper.GetAuthority(),
+				Params: types.Params{
+					MintDenom:     sdk.DefaultBondDenom,
+					InflationCoef: math.LegacyNewDecWithPrec(73, 2),
+					InflationMax:  &validInfMin,
+					InflationMin:  &validInfMax,
+					BlocksPerYear: uint64(60 * 60 * 8766 / 5),
+				},
+			},
+			expectErr: true,
+		},
+		{
+			name: "set full valid params with boundaries",
+			request: &types.MsgUpdateParams{
+				Authority: s.mintKeeper.GetAuthority(),
+				Params: types.Params{
+					MintDenom:     sdk.DefaultBondDenom,
+					InflationCoef: math.LegacyNewDecWithPrec(73, 2),
+					InflationMax:  &validInfMax,
+					InflationMin:  &validInfMin,
+					BlocksPerYear: uint64(60 * 60 * 8766 / 5),
+				},
+			},
+			expectErr: false,
+		},
+		{
+			name: "set full valid params without boundaries",
 			request: &types.MsgUpdateParams{
 				Authority: s.mintKeeper.GetAuthority(),
 				Params: types.Params{
 					MintDenom:     sdk.DefaultBondDenom,
 					InflationCoef: math.LegacyNewDecWithPrec(73, 2),
+					InflationMax:  nil,
+					InflationMin:  nil,
 					BlocksPerYear: uint64(60 * 60 * 8766 / 5),
 				},
 			},

x/mint/simulation/genesis_test.go

@@ -45,7 +45,7 @@ func TestRandomizedGenState(t *testing.T) {
 
 	inflationCoef := math.LegacyNewDecWithPrec(3, 2)
 	bondedRatio := math.LegacyNewDecWithPrec(2, 1)
-	minter, _ := types.NewMinterWithInflationCoef(inflationCoef, bondedRatio, simState.InitialStake)
+	minter, _ := types.NewMinterWithInflationCoef(inflationCoef, bondedRatio, nil, nil, simState.InitialStake)
 
 	require.Equal(t, uint64(6311520), mintGenesis.Params.BlocksPerYear)
 	require.Equal(t, "0.073000000000000000", mintGenesis.Params.InflationCoef.String())

x/mint/types/mint.pb.go

@@ -26,8 +26,12 @@ func NewMinterWithInitialInflation(inflation math.LegacyDec) Minter {
 }
 
 // NewMinterWithInflationCoef returns a new Minter with updated inflation and annual provisions values.
-func NewMinterWithInflationCoef(inflationCoef math.LegacyDec, bondedRatio math.LegacyDec, totalSupply math.Int) (Minter, error) {
-	inflationRate, err := inflationRate(inflationCoef, bondedRatio)
+func NewMinterWithInflationCoef(
+	inflationCoef, bondedRatio math.LegacyDec,
+	minBound, maxBound *math.LegacyDec,
+	totalSupply math.Int,
+) (Minter, error) {
+	inflationRate, err := inflationRate(inflationCoef, bondedRatio, minBound, maxBound)
 	if err != nil {
 		return Minter{}, err
 	}
@@ -55,12 +59,20 @@ func (m Minter) Validate() error {
 
 // inflationRate returns the inflation rate computed from the current bonded ratio
 // and the inflation parameter.
-func inflationRate(inflationCoef math.LegacyDec, bondedRatio math.LegacyDec) (math.LegacyDec, error) {
+func inflationRate(inflationCoef, bondedRatio math.LegacyDec, minBound, maxBound *math.LegacyDec) (math.LegacyDec, error) {
 	if bondedRatio.IsZero() {
 		return math.LegacyZeroDec(), ErrBondedRatioIsZero
 	}
 
-	return inflationCoef.Quo(bondedRatio), nil
+	rate := inflationCoef.Quo(bondedRatio)
+	if minBound != nil {
+		rate = math.LegacyMaxDec(rate, *minBound)
+	}
+	if maxBound != nil {
+		rate = math.LegacyMinDec(rate, *maxBound)
+	}
+
+	return rate, nil
 }
 
 // BlockProvision returns the provisions for a block based on the annual