test: triedb.Config.DBOverride and routing

triedb/database.libevm.go

@@ -40,9 +40,12 @@ type ReaderProvider interface {
 	Reader(common.Hash) (database.Reader, error)
 }
 
-// A BackendConstructor constructs alternative backend implements. The returned
-// type MUST be either a [HashBackend] or a [PathBackend].
-type BackendConstructor func(ethdb.Database, *Config) interface {
+// A BackendConstructor constructs alternative backend implementations.
+type BackendConstructor func(ethdb.Database, *Config) BackendOverride
+
+// A BackendOverride is an arbitrary implementation of a [Database] backend. It
+// MUST be either a [HashBackend] or a [PathBackend].
+type BackendOverride interface {
 	Backend
 	ReaderProvider
 }
@@ -54,7 +57,7 @@ func (db *Database) overrideBackend(diskdb ethdb.Database, config *Config) {
 	if config.HashDB != nil || config.PathDB != nil {
 		log.Crit("Database override provided when 'hash' or 'path' mode are configured")
 	}
-	db.backend.Close() //nolint:gsec // geth defaults to hashdb instances, which always return nil from Close()
+	db.backend.Close() //nolint:gosec // geth defaults to hashdb instances, which always return nil from Close()
 
 	db.backend = config.DBOverride(diskdb, config)
 	switch db.backend.(type) {

triedb/database.libevm_test.go

@@ -0,0 +1,54 @@
+// Copyright 2024 the libevm authors.
+//
+// The libevm additions to go-ethereum are free software: you can redistribute
+// them and/or modify them under the terms of the GNU Lesser General Public License
+// as published by the Free Software Foundation, either version 3 of the License,
+// or (at your option) any later version.
+//
+// The libevm additions are distributed in the hope that they will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
+// General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see
+// <http://www.gnu.org/licenses/>.
+
+package triedb
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/ava-labs/libevm/common"
+	"github.com/ava-labs/libevm/ethdb"
+	"github.com/ava-labs/libevm/triedb/database"
+)
+
+func TestDBOverride(t *testing.T) {
+	config := &Config{
+		DBOverride: func(d ethdb.Database, c *Config) BackendOverride {
+			return override{}
+		},
+	}
+
+	db := NewDatabase(nil, config)
+	got, err := db.Reader(common.Hash{})
+	require.NoError(t, err)
+	if _, ok := got.(reader); !ok {
+		t.Errorf("with non-nil %T.DBOverride, %T.Reader() got concrete type %T; want %T", config, db, got, reader{})
+	}
+}
+
+type override struct {
+	PathBackend
+}
+
+type reader struct {
+	database.Reader
+}
+
+func (override) Reader(common.Hash) (database.Reader, error) {
+	return reader{}, nil
+}