evm: implement vm.GetHashFn (#620)

* evm: implement vm.GetHashFn

* check nil case

* test

* handle 3 cases

* use switch statement

* stateDB tests

* abci changes

* fix LGTM issue

* final tests

* changelog

* remove epoch

* update test

* clean test

* rm epoch

x/evm/keeper/abci.go

@@ -8,6 +8,8 @@ import (
 	sdk "github.com/cosmos/cosmos-sdk/types"
 
 	ethtypes "github.com/ethereum/go-ethereum/core/types"
+
+	"github.com/cosmos/ethermint/x/evm/types"
 )
 
 // BeginBlock sets the block hash -> block height map for the previous block height
@@ -29,18 +31,25 @@ func (k *Keeper) BeginBlock(ctx sdk.Context, req abci.RequestBeginBlock) {
 
 // EndBlock updates the accounts and commits state objects to the KV Store, while
 // deleting the empty ones. It also sets the bloom filers for the request block to
-// the store. The EVM end block loginc doesn't update the validator set, thus it returns
+// the store. The EVM end block logic doesn't update the validator set, thus it returns
 // an empty slice.
 func (k Keeper) EndBlock(ctx sdk.Context, req abci.RequestEndBlock) []abci.ValidatorUpdate {
 	// Gas costs are handled within msg handler so costs should be ignored
 	ctx = ctx.WithGasMeter(sdk.NewInfiniteGasMeter())
 
+	// Set the hash for the current height.
+	// NOTE: we set the hash here instead of on BeginBlock in order to set the final block prior to
+	// an upgrade. If we set it on BeginBlock the last block from prior to the upgrade wouldn't be
+	// included on the store.
+	hash := types.HashFromContext(ctx)
+	k.SetHeightHash(ctx, uint64(ctx.BlockHeight()), hash)
+
 	// Update account balances before committing other parts of state
 	k.UpdateAccounts(ctx)
 
 	// Commit state objects to KV store
-	_, err := k.Commit(ctx, true)
-	if err != nil {
+	if _, err := k.Commit(ctx, true); err != nil {
+		k.Logger(ctx).Error("failed to commit state objects", "error", err, "height", ctx.BlockHeight())
 		panic(err)
 	}
 

x/evm/keeper/keeper.go

@@ -88,6 +88,21 @@ func (k Keeper) SetBlockHash(ctx sdk.Context, hash []byte, height int64) {
 	store.Set(hash, bz)
 }
 
+// ----------------------------------------------------------------------------
+// Epoch Height -> hash mapping functions
+// Required by EVM context's GetHashFunc
+// ----------------------------------------------------------------------------
+
+// GetHeightHash returns the block header hash associated with a given block height and chain epoch number.
+func (k Keeper) GetHeightHash(ctx sdk.Context, height uint64) common.Hash {
+	return k.CommitStateDB.WithContext(ctx).GetHeightHash(height)
+}
+
+// SetHeightHash sets the block header hash associated with a given height.
+func (k Keeper) SetHeightHash(ctx sdk.Context, height uint64, hash common.Hash) {
+	k.CommitStateDB.WithContext(ctx).SetHeightHash(height, hash)
+}
+
 // ----------------------------------------------------------------------------
 // Block bloom bits mapping functions
 // Required by Web3 API.

x/evm/keeper/keeper_test.go

@@ -42,7 +42,7 @@ func (suite *KeeperTestSuite) SetupTest() {
 	checkTx := false
 
 	suite.app = app.Setup(checkTx)
-	suite.ctx = suite.app.BaseApp.NewContext(checkTx, abci.Header{Height: 1, ChainID: "3", Time: time.Now().UTC()})
+	suite.ctx = suite.app.BaseApp.NewContext(checkTx, abci.Header{Height: 1, ChainID: "ethermint-3", Time: time.Now().UTC()})
 	suite.querier = keeper.NewQuerier(suite.app.EvmKeeper)
 	suite.address = ethcmn.HexToAddress(addrHex)