fix(binder): normalize db tags

binder_struct.go

@@ -25,7 +25,9 @@ func newStructBinder(t reflect.Type, v reflect.Value) Binder {
 		}
 
 		if tagName != "" {
-			sb.fieldIndexes[tagName] = i
+			// Normalize tag name to match column name processing: remove underscores and lowercase
+			normalizedTag := strings.ToLower(strings.ReplaceAll(tagName, "_", ""))
+			sb.fieldIndexes[normalizedTag] = i
 			sb.fieldColumnNames = append(sb.fieldColumnNames, tagName)
 			continue
 

binder_test.go

@@ -1 +1,94 @@
 package sqle
+
+import (
+	"context"
+	"database/sql"
+	"testing"
+
+	_ "github.com/mattn/go-sqlite3"
+	"github.com/stretchr/testify/require"
+)
+
+type UserWithUnderscoreTag struct {
+	ID        int    `db:"id"`
+	FirstName string `db:"first_name"`
+	LastName  string `db:"last_name"`
+	Email     string `db:"email"`
+}
+
+type UserWithoutTag struct {
+	ID        int
+	FirstName string
+	LastName  string
+	Email     string
+}
+
+func TestStructBinderWithUnderscoreTags(t *testing.T) {
+	d, err := sql.Open("sqlite3", "file::memory:?cache=shared")
+	require.NoError(t, err)
+	defer d.Close()
+
+	_, err = d.Exec("CREATE TABLE users (id INTEGER PRIMARY KEY, first_name TEXT, last_name TEXT, email TEXT)")
+	require.NoError(t, err)
+
+	_, err = d.Exec("INSERT INTO users (id, first_name, last_name, email) VALUES (1, 'John', 'Doe', 'john@example.com')")
+	require.NoError(t, err)
+
+	db := Open(d)
+
+	t.Run("db_tag_with_underscores_should_work", func(t *testing.T) {
+		var user UserWithUnderscoreTag
+		err := db.QueryRow("SELECT id, first_name, last_name, email FROM users WHERE id = 1").Bind(&user)
+		require.NoError(t, err)
+		require.Equal(t, 1, user.ID)
+		require.Equal(t, "John", user.FirstName)
+		require.Equal(t, "Doe", user.LastName)
+		require.Equal(t, "john@example.com", user.Email)
+	})
+
+	t.Run("without_tag_should_work", func(t *testing.T) {
+		var user UserWithoutTag
+		err := db.QueryRow("SELECT id, first_name, last_name, email FROM users WHERE id = 1").Bind(&user)
+		require.NoError(t, err)
+		require.Equal(t, 1, user.ID)
+		require.Equal(t, "John", user.FirstName)
+		require.Equal(t, "Doe", user.LastName)
+		require.Equal(t, "john@example.com", user.Email)
+	})
+
+	t.Run("uppercase_column_names_should_work", func(t *testing.T) {
+		var user UserWithUnderscoreTag
+		err := db.QueryRow("SELECT id, FIRST_NAME, LAST_NAME, EMAIL FROM users WHERE id = 1").Bind(&user)
+		require.NoError(t, err)
+		require.Equal(t, 1, user.ID)
+		require.Equal(t, "John", user.FirstName)
+		require.Equal(t, "Doe", user.LastName)
+		require.Equal(t, "john@example.com", user.Email)
+	})
+
+	t.Run("mixed_case_column_names_should_work", func(t *testing.T) {
+		var user UserWithUnderscoreTag
+		err := db.QueryRow("SELECT id, First_Name, Last_Name, Email FROM users WHERE id = 1").Bind(&user)
+		require.NoError(t, err)
+		require.Equal(t, 1, user.ID)
+		require.Equal(t, "John", user.FirstName)
+		require.Equal(t, "Doe", user.LastName)
+		require.Equal(t, "john@example.com", user.Email)
+	})
+
+	t.Run("slice_binding_should_work", func(t *testing.T) {
+		_, err = d.Exec("INSERT INTO users (id, first_name, last_name, email) VALUES (2, 'Jane', 'Smith', 'jane@example.com')")
+		require.NoError(t, err)
+
+		var users []UserWithUnderscoreTag
+		rows, err := db.QueryBuilder(context.Background(), New("SELECT id, first_name, last_name, email FROM users ORDER BY id"))
+		require.NoError(t, err)
+		err = rows.Bind(&users)
+		require.NoError(t, err)
+		require.Len(t, users, 2)
+		require.Equal(t, 1, users[0].ID)
+		require.Equal(t, "John", users[0].FirstName)
+		require.Equal(t, 2, users[1].ID)
+		require.Equal(t, "Jane", users[1].FirstName)
+	})
+}