get_namespace_name now preserves leading underscore on relative import

lark/load_grammar.py

@@ -597,6 +597,8 @@ def import_from_grammar_into_namespace(grammar, namespace, aliases):
         try:
             return aliases[name].value
         except KeyError:
+            if name[0] == '_':
+                return '_%s__%s' % (namespace, name[1:])
             return '%s__%s' % (namespace, name)
 
     to_import = list(bfs(aliases, rule_dependencies))

tests/grammars/leading_underscore_grammar.lark

@@ -0,0 +1,6 @@
+A: "A"
+
+_SEP: "x"
+_a: A
+
+c: _a _SEP

tests/test_parser.py

@@ -1099,6 +1099,11 @@ def _make_parser_test(LEXER, PARSER):
             x = l.parse('12 capybaras')
             self.assertEqual(x.children, ['12', 'capybaras'])
 
+        def test_relative_import_preserves_leading_underscore(self):
+            l = _Lark_open("test_relative_import_preserves_leading_underscore.lark", rel_to=__file__)
+            x = l.parse('Ax')
+            self.assertEqual(next(x.find_data('c')).children, ['A'])
+
         def test_import_errors(self):
             grammar = """
             start: NUMBER WORD

tests/test_relative_import_preserves_leading_underscore.lark

@@ -0,0 +1,3 @@
+start: c
+
+%import .grammars.leading_underscore_grammar.c