fix(x/gov): migrations from 2 to 3 (min proposer deposit) (#298)

* git checkout -b roman/fix-gov-migrations

* register migrations

(cherry picked from commit 51bfa90)

# Conflicts:
#	x/gov/legacy/v3/store.go

x/gov/keeper/migrations.go

@@ -3,6 +3,7 @@ package keeper
 import (
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	v043 "github.com/cosmos/cosmos-sdk/x/gov/legacy/v043"
+	v3 "github.com/cosmos/cosmos-sdk/x/gov/legacy/v3"
 )
 
 // Migrator is a struct for handling in-place store migrations.
@@ -19,3 +20,8 @@ func NewMigrator(keeper Keeper) Migrator {
 func (m Migrator) Migrate1to2(ctx sdk.Context) error {
 	return v043.MigrateStore(ctx, m.keeper.storeKey, m.keeper.cdc)
 }
+
+// Migrate2to3 migrates from version 2 to 3.
+func (m Migrator) Migrate2to3(ctx sdk.Context) error {
+	return v3.MigrateStore(ctx, m.keeper.paramSpace)
+}

x/gov/legacy/v3/store.go

@@ -0,0 +1,28 @@
+package v3
+
+import (
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	"github.com/cosmos/cosmos-sdk/x/gov/types"
+)
+
+var minInitialDepositRatio = sdk.NewDec(25).Quo(sdk.NewDec(100))
+
+// MigrateStore performs in-place store migrations for consensus version 3
+// in the gov module.
+// Please note that this is the first version that switches from using
+// SDK versioning (v043 etc) for package names to consensus versioning
+// of the gov module.
+// The migration includes:
+//
+// - Setting the minimum deposit param in the paramstore.
+func MigrateStore(ctx sdk.Context, paramstore types.ParamSubspace) error {
+	migrateParamsStore(ctx, paramstore)
+	return nil
+}
+
+func migrateParamsStore(ctx sdk.Context, paramstore types.ParamSubspace) {
+	var depositParams types.DepositParams
+	paramstore.Get(ctx, types.ParamStoreKeyDepositParams, &depositParams)
+	depositParams.MinInitialDepositRatio = minInitialDepositRatio
+	paramstore.Set(ctx, types.ParamStoreKeyDepositParams, depositParams)
+}

x/gov/module.go

@@ -161,6 +161,10 @@ func (am AppModule) RegisterServices(cfg module.Configurator) {
 	if err != nil {
 		panic(err)
 	}
+	cfg.RegisterMigration(types.ModuleName, 2, m.Migrate2to3)
+	if err != nil {
+		panic(err)
+	}
 }
 
 // InitGenesis performs genesis initialization for the gov module. It returns