refactor(x/mint)!: avoid writing same minter and use millisecond precision for minting (#20747)

x/mint/epoch_hooks.go

@@ -20,11 +20,17 @@ func (am AppModule) BeforeEpochStart(ctx context.Context, epochIdentifier string
 		return err
 	}
 
+	oldMinter := minter
+
 	err = am.mintFn(ctx, am.keeper.Environment, &minter, epochIdentifier, epochNumber)
 	if err != nil {
 		return err
 	}
 
+	if minter.IsEqual(oldMinter) {
+		return nil
+	}
+
 	return am.keeper.Minter.Set(ctx, minter)
 }
 

x/mint/keeper/abci.go

@@ -18,6 +18,8 @@ func (k Keeper) BeginBlocker(ctx context.Context, mintFn types.MintFn) error {
 		return err
 	}
 
+	oldMinter := minter
+
 	// we pass -1 as epoch number to indicate that this is not an epoch minting,
 	// but a regular block minting. Same with epoch id "block".
 	err = mintFn(ctx, k.Environment, &minter, "block", -1)
@@ -25,5 +27,9 @@ func (k Keeper) BeginBlocker(ctx context.Context, mintFn types.MintFn) error {
 		return err
 	}
 
+	if minter.IsEqual(oldMinter) {
+		return nil
+	}
+
 	return k.Minter.Set(ctx, minter)
 }

x/mint/keeper/keeper_test.go

@@ -1,11 +1,13 @@
 package keeper_test
 
 import (
+	"context"
 	"testing"
 
 	"github.com/golang/mock/gomock"
 	"github.com/stretchr/testify/suite"
 
+	"cosmossdk.io/core/appmodule"
 	"cosmossdk.io/log"
 	"cosmossdk.io/math"
 	storetypes "cosmossdk.io/store/types"
@@ -152,6 +154,17 @@ func (s *KeeperTestSuite) TestBeginBlocker() {
 	newMinter, err := s.mintKeeper.Minter.Get(s.ctx)
 	s.NoError(err)
 	s.NotEqual(minter, newMinter)
+
+	// now use a mintfn that doesn't do anything
+	err = s.mintKeeper.BeginBlocker(s.ctx, func(ctx context.Context, env appmodule.Environment, minter *types.Minter, epochId string, epochNumber int64) error {
+		return nil
+	})
+	s.NoError(err)
+
+	// get minter again and compare
+	unchangedMinter, err := s.mintKeeper.Minter.Get(s.ctx)
+	s.NoError(err)
+	s.Equal(newMinter, unchangedMinter)
 }
 
 func (s *KeeperTestSuite) TestMigrator() {

x/mint/types/minter.go

@@ -1,6 +1,7 @@
 package types
 
 import (
+	"bytes"
 	"fmt"
 
 	"cosmossdk.io/math"
@@ -80,3 +81,20 @@ func (m Minter) BlockProvision(params Params) sdk.Coin {
 	provisionAmt := m.AnnualProvisions.QuoInt(math.NewInt(int64(params.BlocksPerYear)))
 	return sdk.NewCoin(params.MintDenom, provisionAmt.TruncateInt())
 }
+
+// IsEqual returns true if two minters are equal, it checks all the fields
+func (m Minter) IsEqual(minter Minter) bool {
+	if !m.Inflation.Equal(minter.Inflation) {
+		return false
+	}
+
+	if !m.AnnualProvisions.Equal(minter.AnnualProvisions) {
+		return false
+	}
+
+	if !bytes.Equal(m.Data, minter.Data) {
+		return false
+	}
+
+	return true
+}