Add error check for nil pointers used as arguments to QueryOne()

ksql.go

@@ -248,16 +248,22 @@ func (c DB) QueryOne(
 	query string,
 	params ...interface{},
 ) error {
-	t := reflect.TypeOf(record)
+	v := reflect.ValueOf(record)
+	t := v.Type()
 	if t.Kind() != reflect.Ptr {
 		return fmt.Errorf("ksql: expected to receive a pointer to struct, but got: %T", record)
 	}
-	t = t.Elem()
-	if t.Kind() != reflect.Struct {
+
+	if v.IsNil() {
+		return fmt.Errorf("ksql: expected a valid pointer to struct as argument but received a nil pointer: %v", record)
+	}
+
+	tStruct := t.Elem()
+	if tStruct.Kind() != reflect.Struct {
 		return fmt.Errorf("ksql: expected to receive a pointer to struct, but got: %T", record)
 	}
 
-	info := kstructs.GetTagInfo(t)
+	info := kstructs.GetTagInfo(tStruct)
 
 	firstToken := strings.ToUpper(getFirstToken(query))
 	if info.IsNestedStruct && firstToken == "SELECT" {
@@ -266,7 +272,7 @@ func (c DB) QueryOne(
 	}
 
 	if firstToken == "FROM" {
-		selectPrefix, err := buildSelectQuery(c.dialect, t, info, selectQueryCache[c.dialect.DriverName()])
+		selectPrefix, err := buildSelectQuery(c.dialect, tStruct, info, selectQueryCache[c.dialect.DriverName()])
 		if err != nil {
 			return err
 		}
@@ -286,7 +292,7 @@ func (c DB) QueryOne(
 		return ErrRecordNotFound
 	}
 
-	err = scanRows(c.dialect, rows, record)
+	err = scanRowsFromType(c.dialect, rows, record, t, v)
 	if err != nil {
 		return err
 	}
@@ -860,6 +866,16 @@ func (nopScanner) Scan(value interface{}) error {
 func scanRows(dialect Dialect, rows Rows, record interface{}) error {
 	v := reflect.ValueOf(record)
 	t := v.Type()
+	return scanRowsFromType(dialect, rows, record, t, v)
+}
+
+func scanRowsFromType(
+	dialect Dialect,
+	rows Rows,
+	record interface{},
+	t reflect.Type,
+	v reflect.Value,
+) error {
 	if t.Kind() != reflect.Ptr {
 		return fmt.Errorf("ksql: expected record to be a pointer to struct, but got: %T", record)
 	}

ksql_test.go

@@ -594,6 +594,17 @@ func TestQueryOne(t *testing.T) {
 				assert.NotEqual(t, nil, err)
 			})
 
+			t.Run("should report error if it receives a nil pointer to a struct", func(t *testing.T) {
+				db, closer := connectDB(t, config)
+				defer closer.Close()
+
+				ctx := context.Background()
+				c := newTestDB(db, config.driver)
+				var user *User
+				err := c.QueryOne(ctx, user, `SELECT * FROM users`)
+				assert.NotEqual(t, nil, err)
+			})
+
 			t.Run("should report error if the query is not valid", func(t *testing.T) {
 				db, closer := connectDB(t, config)
 				defer closer.Close()