feat(x/mint): Add max supply param (#19896)

Co-authored-by: Marko <marko@baricevic.me>

tests/e2e/mint/grpc.go

@@ -29,7 +29,7 @@ func (s *E2ETestSuite) TestQueryGRPC() {
 			&minttypes.QueryParamsResponse{},
 			&minttypes.QueryParamsResponse{
 				Params: minttypes.NewParams("stake", math.LegacyNewDecWithPrec(13, 2), math.LegacyNewDecWithPrec(100, 2),
-					math.LegacyNewDec(1), math.LegacyNewDecWithPrec(67, 2), (60 * 60 * 8766 / 5)),
+					math.LegacyNewDec(1), math.LegacyNewDecWithPrec(67, 2), (60 * 60 * 8766 / 5), math.ZeroInt()),
 			},
 		},
 		{

x/mint/CHANGELOG.md

@@ -27,6 +27,8 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### Features
 
+* [19896](https://github.com/cosmos/cosmos-sdk/pull/19896) Added a new max supply genesis param to existing params.
+
 ### Improvements
 
 ### API Breaking Changes

x/mint/README.md

@@ -63,17 +63,21 @@ https://github.com/cosmos/cosmos-sdk/blob/v0.47.0-rc1/proto/cosmos/mint/v1beta1/
 
 The mint module stores its params in state with the prefix of `0x01`,
 it can be updated with governance or the address with authority.
+**Note:** With the latest update, the addition of the `MaxSupply` parameter allows controlling the maximum supply of tokens minted by the module. 
+A value of `0` indicates an unlimited supply.
 
 * Params: `mint/params -> legacy_amino(params)`
 
 ```protobuf reference
-https://github.com/cosmos/cosmos-sdk/blob/v0.47.0-rc1/proto/cosmos/mint/v1beta1/mint.proto#L26-L59
+https://github.com/cosmos/cosmos-sdk/blob/7068d0da52d954430054768b2c56aff44666933b/x/mint/proto/cosmos/mint/v1beta1/mint.proto#L26-L68
 ```
 
 ## Begin-Block
 
 Minting parameters are recalculated and inflation paid at the beginning of each block.
 
+The minting logic in the `BeginBlocker` function provides an optional feature for controlling token minting based on the maximum allowable supply (MaxSupply). This feature allows users to adjust the minting process according to their specific requirements and use cases. However, it's important to note that the MaxSupply parameter is independent of the minting process and assumes that any adjustments to the total supply, including burning tokens, are handled by external modules.
+
 ### Inflation rate calculation
 
 Inflation rate is calculated using an "inflation calculation function" that's
@@ -136,15 +140,17 @@ BlockProvision(params Params) sdk.Coin {
 ## Parameters
 
 The minting module contains the following parameters:
+Note: `0` indicates unlimited supply for MaxSupply param
 
-| Key                 | Type            | Example                |
-|---------------------|-----------------|------------------------|
-| MintDenom           | string          | "uatom"                |
-| InflationRateChange | string (dec)    | "0.130000000000000000" |
-| InflationMax        | string (dec)    | "0.200000000000000000" |
-| InflationMin        | string (dec)    | "0.070000000000000000" |
-| GoalBonded          | string (dec)    | "0.670000000000000000" |
-| BlocksPerYear       | string (uint64) | "6311520"              |
+| Key                 | Type             | Example                |
+|---------------------|------------------|------------------------|
+| MintDenom           | string           | "uatom"                |
+| InflationRateChange | string (dec)     | "0.130000000000000000" |
+| InflationMax        | string (dec)     | "0.200000000000000000" |
+| InflationMin        | string (dec)     | "0.070000000000000000" |
+| GoalBonded          | string (dec)     | "0.670000000000000000" |
+| BlocksPerYear       | string (uint64)  | "6311520"              |
+| MaxSupply           | string (math.Int)| "0"                    |
 
 
 ## Events
@@ -232,6 +238,7 @@ inflation_max: "0.200000000000000000"
 inflation_min: "0.070000000000000000"
 inflation_rate_change: "0.130000000000000000"
 mint_denom: stake
+max_supply: "0"
 ```
 
 ### gRPC
@@ -306,7 +313,8 @@ Example Output:
     "inflationMax": "200000000000000000",
     "inflationMin": "70000000000000000",
     "goalBonded": "670000000000000000",
-    "blocksPerYear": "6311520"
+    "blocksPerYear": "6311520",
+    "maxSupply": "0",
   }
 }
 ```
@@ -377,7 +385,8 @@ Example Output:
     "inflationMax": "200000000000000000",
     "inflationMin": "70000000000000000",
     "goalBonded": "670000000000000000",
-    "blocksPerYear": "6311520"
+    "blocksPerYear": "6311520",
+    "maxSupply": "0",
   }
 }
 ```

x/mint/keeper/abci.go

@@ -36,19 +36,43 @@ func (k Keeper) BeginBlocker(ctx context.Context, ic types.InflationCalculationF
 		return err
 	}
 
+	// update minter's inflation and annual provisions
 	minter.Inflation = ic(ctx, minter, params, bondedRatio)
 	minter.AnnualProvisions = minter.NextAnnualProvisions(params, totalStakingSupply)
 	if err = k.Minter.Set(ctx, minter); err != nil {
 		return err
 	}
 
-	// mint coins, update supply
+	// calculate minted coins
 	mintedCoin := minter.BlockProvision(params)
 	mintedCoins := sdk.NewCoins(mintedCoin)
 
-	err = k.MintCoins(ctx, mintedCoins)
-	if err != nil {
-		return err
+	maxSupply := params.MaxSupply
+	totalSupply := k.bankKeeper.GetSupply(ctx, params.MintDenom).Amount // fetch total supply from the bank module
+
+	// if maxSupply is not infinite, check against max_supply parameter
+	if !maxSupply.IsZero() {
+		if totalSupply.Add(mintedCoins.AmountOf(params.MintDenom)).GT(maxSupply) {
+			// calculate the difference between maxSupply and totalSupply
+			diff := maxSupply.Sub(totalSupply)
+			// mint the difference
+			diffCoin := sdk.NewCoin(params.MintDenom, diff)
+			diffCoins := sdk.NewCoins(diffCoin)
+
+			// mint coins
+			if err := k.MintCoins(ctx, diffCoins); err != nil {
+				return err
+			}
+			mintedCoins = diffCoins
+		}
+	}
+
+	// mint coins if maxSupply is infinite or total staking supply is less than maxSupply
+	if maxSupply.IsZero() || totalSupply.Add(mintedCoins.AmountOf(params.MintDenom)).LT(maxSupply) {
+		// mint coins
+		if err := k.MintCoins(ctx, mintedCoins); err != nil {
+			return err
+		}
 	}
 
 	// send the minted coins to the fee collector account

x/mint/keeper/genesis_test.go

@@ -71,6 +71,7 @@ func (s *GenesisTestSuite) TestImportExportGenesis() {
 		math.LegacyNewDecWithPrec(9, 2),
 		math.LegacyNewDecWithPrec(69, 2),
 		uint64(60*60*8766/5),
+		math.ZeroInt(),
 	)
 
 	err := s.keeper.InitGenesis(s.sdkCtx, s.accountKeeper, genesisState)