Add a warning to the Python version of the parser (#30)

Adding a warning that gets logged whenever the slow Python version of the parser is used.

src/pytsql/grammar/__init__.py

@@ -1 +1 @@
-from .sa_tsql import parse, SA_ErrorListener, tsqlParser
+from .sa_tsql import parse, SA_ErrorListener, tsqlParser, USE_CPP_IMPLEMENTATION

src/pytsql/grammar/sa_tsql.py

@@ -1,6 +1,5 @@
 # This file was auto-generated by speedy-antlr-tool v1.3.1
 #  https://github.com/amykyta3/speedy-antlr-tool
-
 import sys
 import types
 from typing import Optional

src/pytsql/tsql.py

@@ -1,5 +1,6 @@
 import logging
 import re
+import warnings
 from pathlib import Path
 from re import Match
 from typing import Any, Dict, List, Optional, Union
@@ -9,7 +10,7 @@
 from antlr4 import InputStream, Token
 from sqlalchemy.engine import Connection
 
-from pytsql.grammar import SA_ErrorListener, parse, tsqlParser
+from pytsql.grammar import USE_CPP_IMPLEMENTATION, SA_ErrorListener, parse, tsqlParser
 
 _REPLACE_START = "<replace>"
 _REPLACE_END = "</replace>"
@@ -143,6 +144,13 @@ def syntaxError(
 
 
 def _split(code: str) -> List[str]:
+    if not USE_CPP_IMPLEMENTATION:
+        warnings.warn(
+            "Can not find C++ version of the parser, Python version will be used instead."
+            " Something is likely wrong with your installation of the package,"
+            " and is preventing the use of the faster C++ parser."
+        )
+
     logging.info("Started SQL script parsing")
 
     # The default error listener only prints to the console without raising exceptions.

tests/unit/test_py_vs_cpp.py

@@ -8,6 +8,7 @@
 from antlr4.Token import CommonToken
 from antlr4.tree.Tree import TerminalNodeImpl
 
+from pytsql import tsql
 from pytsql.grammar import sa_tsql
 from pytsql.tsql import _split
 
@@ -135,3 +136,9 @@ def test_compare_py_and_cpp__split(py_parse_mock, cpp_parse_mock, seed):
     cpp_parse_mock.assert_called_once()
 
     assert py_result == cpp_result
+
+
+def test__py_parse__warns():
+    tsql.USE_CPP_IMPLEMENTATION = False
+    with pytest.warns(match=r"Can not find C\+\+ version of the parser"):
+        _split("")