:fix: Correct #24. Problem with backslash

Author: Aunsiels

pyformlang/regular_expression/regex_reader.py

@@ -227,7 +227,7 @@ def _pre_process_regex(regex: str) -> str:
         if not previous_is_escape and (current_c in SPECIAL_SYMBOLS) and \
                 pos != len(regex) - 1 and regex[pos + 1] != " ":
             res.append(" ")
-        previous_is_escape = current_c == "\\"
+        previous_is_escape = current_c == "\\" and not previous_is_escape
         pos += 1
     return "".join(res)
 

pyformlang/regular_expression/tests/test_python_regex.py

@@ -203,8 +203,8 @@ def _test_compare(self, regex, s_test):
         self.assertEqual(r_python.fullmatch(s_test) is not None, r_pyformlang.accepts(s_test))
 
     def test_backslash(self):
-        self._test_compare(".*", "]")
         self._test_compare(".*", "\\")
+        self._test_compare(".*", "]")
 
     def test_escape_dot(self):
         self._test_compare("\\.", ".")
@@ -246,7 +246,7 @@ def test_brackets_backslash_middle(self):
         self._test_compare(r"[a\b]", "\\b")
         self._test_compare(r"[a\b]", "\\")
 
-    def test_backslash(self):
+    def test_backslash2(self):
         self._test_compare(r"\t", "t")
         self._test_compare(r"\t", "\t")
         self._test_compare(r"\t", "\\t")

pyformlang/regular_expression/tests/test_regex.py

@@ -290,3 +290,7 @@ def test_backslash_b(self):
         self.assertTrue(Regex("( a | \b )").accepts("\b"))
         self.assertTrue(Regex("( a | \b )").accepts("a"))
         self.assertFalse(Regex("( a | \b )").accepts("b"))
+
+    def test_backslash(self):
+        self.assertTrue(Regex("(\\\\|])").accepts("\\"))
+        self.assertTrue(Regex("(\\\\|])").accepts("]"))