feemarket: migration (#1002)

* increase feemarket's consensus version and add migration handler

Closes: #1001

* unit test

* fix linter

x/feemarket/keeper/migrations.go

@@ -1,5 +1,14 @@
 package keeper
 
+import (
+	"math/big"
+
+	sdk "github.com/cosmos/cosmos-sdk/types"
+)
+
+// KeyPrefixBaseFeeV1 is the base fee key prefix used in version 1
+var KeyPrefixBaseFeeV1 = []byte{2}
+
 // Migrator is a struct for handling in-place store migrations.
 type Migrator struct {
 	keeper Keeper
@@ -11,3 +20,14 @@ func NewMigrator(keeper Keeper) Migrator {
 		keeper: keeper,
 	}
 }
+
+func (m Migrator) Migrate1to2(ctx sdk.Context) error {
+	store := ctx.KVStore(m.keeper.storeKey)
+	bz := store.Get(KeyPrefixBaseFeeV1)
+	if len(bz) > 0 {
+		baseFee := new(big.Int).SetBytes(bz)
+		m.keeper.SetBaseFee(ctx, baseFee)
+	}
+	store.Delete(KeyPrefixBaseFeeV1)
+	return nil
+}

x/feemarket/keeper/migrations_test.go

@@ -0,0 +1,18 @@
+package keeper_test
+
+import (
+	"math/big"
+
+	"github.com/tharsis/ethermint/x/feemarket/keeper"
+)
+
+func (suite *KeeperTestSuite) TestMigration1To2() {
+	suite.SetupTest()
+	storeKey := suite.app.GetKey("feemarket")
+	store := suite.ctx.KVStore(storeKey)
+	baseFee := big.NewInt(1000)
+	store.Set(keeper.KeyPrefixBaseFeeV1, baseFee.Bytes())
+	m := keeper.NewMigrator(suite.app.FeeMarketKeeper)
+	suite.Require().NoError(m.Migrate1to2(suite.ctx))
+	suite.Require().Equal(baseFee, suite.app.FeeMarketKeeper.GetBaseFee(suite.ctx))
+}