minor refactor

core/blockchain_reader.go

@@ -17,6 +17,7 @@
 package core
 
 import (
+	"errors"
 	"math/big"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -337,7 +338,20 @@ func (bc *BlockChain) State() (*state.StateDB, error) {
 
 // StateAt returns a new mutable state based on a particular point in time.
 func (bc *BlockChain) StateAt(root common.Hash) (*state.StateDB, error) {
-	return state.New(root, bc.stateCache, bc.snaps)
+	stateDb, err := state.New(root, bc.stateCache, bc.snaps)
+	if err != nil {
+		return nil, err
+	}
+
+	// If there's no trie and the specified snapshot is not available, getting
+	// any state will by default return nil.
+	// Instead of that, it will be more useful to return an error to indicate
+	// the state is not available.
+	if stateDb.NoTrie() && stateDb.GetSnap() == nil {
+		return nil, errors.New("state is not available")
+	}
+
+	return stateDb, err
 }
 
 // Config retrieves the chain's fork configuration.

core/state/statedb.go

@@ -71,7 +71,7 @@ type StateDB struct {
 	// It will be updated when the Commit is called.
 	originalRoot common.Hash
 	expectedRoot common.Hash // The state root in the block header
-	stateRoot    common.Hash
+
 	// These maps hold the state changes (including the corresponding
 	// original value) that occurred in this **block**.
 	accounts       map[common.Hash][]byte                    // The mutated accounts in 'slim RLP' encoding
@@ -1193,7 +1193,7 @@ func (s *StateDB) Commit(block uint64, deleteEmptyObjects bool) (common.Hash, er
 		return common.Hash{}, fmt.Errorf("commit aborted due to earlier error: %v", s.dbErr)
 	}
 	// Finalize any pending changes and merge everything into the tries
-	s.stateRoot = s.IntermediateRoot(deleteEmptyObjects)
+	root := s.IntermediateRoot(deleteEmptyObjects)
 
 	// Commit objects to the trie, measuring the elapsed time
 	var (
@@ -1282,15 +1282,15 @@ func (s *StateDB) Commit(block uint64, deleteEmptyObjects bool) (common.Hash, er
 	if s.snap != nil {
 		start := time.Now()
 		// Only update if there's a state transition (skip empty Clique blocks)
-		if parent := s.snap.Root(); parent != s.expectedRoot {
-			if err := s.snaps.Update(s.expectedRoot, parent, s.convertAccountSet(s.stateObjectsDestruct), s.accounts, s.storages); err != nil {
+		if parent := s.snap.Root(); parent != root {
+			if err := s.snaps.Update(root, parent, s.convertAccountSet(s.stateObjectsDestruct), s.accounts, s.storages); err != nil {
 				log.Warn("Failed to update snapshot tree", "from", parent, "to", s.expectedRoot, "err", err)
 			}
 			// Keep 128 diff layers in the memory, persistent layer is 129th.
 			// - head layer is paired with HEAD state
 			// - head-1 layer is paired with HEAD-1 state
 			// - head-127 layer(bottom-most diff layer) is paired with HEAD-127 state
-			if err := s.snaps.Cap(s.expectedRoot, 128); err != nil {
+			if err := s.snaps.Cap(root, 128); err != nil {
 				log.Warn("Failed to cap snapshot tree", "root", s.expectedRoot, "layers", 128, "err", err)
 			}
 		}
@@ -1300,7 +1300,6 @@ func (s *StateDB) Commit(block uint64, deleteEmptyObjects bool) (common.Hash, er
 		s.snap = nil
 	}
 
-	root := s.stateRoot
 	if root == (common.Hash{}) {
 		root = types.EmptyRootHash
 	}
@@ -1429,6 +1428,10 @@ func (s *StateDB) NoTrie() bool {
 	return s.noTrie
 }
 
+func (s *StateDB) GetSnap() snapshot.Snapshot {
+	return s.snap
+}
+
 // Mark that the block is processed by diff layer
 func (s *StateDB) SetExpectedStateRoot(root common.Hash) {
 	s.expectedRoot = root

tests/state_test_util.go

@@ -299,10 +299,7 @@ func (t *StateTest) RunNoVerify(subtest StateSubtest, vmconfig vm.Config, snapsh
 	statedb.AddBalance(block.Coinbase(), new(big.Int))
 
 	// Commit state mutations into database.
-	root := statedb.IntermediateRoot(config.IsEIP158(block.Number()))
-	statedb.SetExpectedStateRoot(root)
-
-	root, _ = statedb.Commit(block.NumberU64(), config.IsEIP158(block.Number()))
+	root, _ := statedb.Commit(block.NumberU64(), config.IsEIP158(block.Number()))
 	return triedb, snaps, statedb, root, err
 }
 
@@ -329,10 +326,7 @@ func MakePreState(db ethdb.Database, accounts core.GenesisAlloc, snapshotter boo
 		}
 	}
 	// Commit and re-open to start with a clean state.
-	root := statedb.IntermediateRoot(false)
-	statedb.SetExpectedStateRoot(root)
-
-	root, _ = statedb.Commit(0, false)
+	root, _ := statedb.Commit(0, false)
 
 	var snaps *snapshot.Tree
 	if snapshotter {