core/state: fix account prefetching for absent accounts (#35256)

core/state/statedb.go

@@ -614,16 +614,17 @@ func (s *StateDB) getStateObject(addr common.Address) *stateObject {
 	}
 	s.AccountReads += time.Since(start)
 
-	// Short circuit if the account is not found
-	if acct == nil {
-		return nil
-	}
-	// Schedule the resolved account for prefetching if it's enabled.
+	// Schedule the account path for prefetching if it's enabled. Even if the
+	// account is absent, the trie path proves its non-existence for witnesses.
 	if s.prefetcher != nil {
 		if err = s.prefetcher.prefetch(common.Hash{}, s.originalRoot, common.Address{}, []common.Address{addr}, nil, true); err != nil {
 			log.Error("Failed to prefetch account", "addr", addr, "err", err)
 		}
 	}
+	// Short circuit if the account is not found
+	if acct == nil {
+		return nil
+	}
 	// Insert into the live set
 	obj := newObject(s, addr, acct)
 	s.setStateObject(obj)

core/state/statedb_test.go

@@ -33,6 +33,7 @@ import (
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/rawdb"
 	"github.com/ethereum/go-ethereum/core/state/snapshot"
+	"github.com/ethereum/go-ethereum/core/stateless"
 	"github.com/ethereum/go-ethereum/core/tracing"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/crypto"
@@ -998,6 +999,45 @@ func TestDeleteCreateRevert(t *testing.T) {
 	}
 }
 
+func TestWitnessIncludesAbsentAccountReads(t *testing.T) {
+	db := NewDatabaseForTesting()
+	state, _ := New(types.EmptyRootHash, db)
+	for i := byte(0); i < 3; i++ {
+		addr := common.Address{i + 1}
+		state.SetBalance(addr, uint256.NewInt(uint64(i+1)), tracing.BalanceChangeUnspecified)
+	}
+	root, err := state.Commit(0, false, false)
+	if err != nil {
+		t.Fatalf("failed to commit initial state: %v", err)
+	}
+	state, err = New(root, db)
+	if err != nil {
+		t.Fatalf("failed to reopen state: %v", err)
+	}
+
+	witness := &stateless.Witness{
+		Codes: make(map[string]struct{}),
+		State: make(map[string]struct{}),
+	}
+	state.StartPrefetcher("test", witness)
+	missing := common.HexToAddress("0x017655eac00c837122cabbbc0dd604a196906648")
+	if balance := state.GetBalance(missing); balance.Sign() != 0 {
+		t.Fatalf("unexpected balance for absent account: %v", balance)
+	}
+	if err := state.Error(); err != nil {
+		t.Fatalf("unexpected state error after read: %v", err)
+	}
+	if got := state.IntermediateRoot(false); got != root {
+		t.Fatalf("unexpected root after read-only access: have %x want %x", got, root)
+	}
+	if err := state.Error(); err != nil {
+		t.Fatalf("unexpected state error after root calculation: %v", err)
+	}
+	if len(witness.State) == 0 {
+		t.Fatal("missing witness nodes for absent account read")
+	}
+}
+
 // TestMissingTrieNodes tests that if the StateDB fails to load parts of the trie,
 // the Commit operation fails with an error
 // If we are missing trie nodes, we should not continue writing to the trie