fix: do not resolve symlinks

gitignore_parser.py

@@ -2,7 +2,7 @@
 import os
 import re
 
-from os.path import dirname
+from os.path import abspath, dirname
 from pathlib import Path
 from typing import Reversible, Union
 
@@ -102,7 +102,7 @@ def rule_from_pattern(pattern, base_path=None, source=None):
         negation=negation,
         directory_only=directory_only,
         anchored=anchored,
-        base_path=Path(base_path) if base_path else None,
+        base_path=_normalize_path(base_path) if base_path else None,
         source=source
     )
 
@@ -125,9 +125,9 @@ def __repr__(self):
     def match(self, abs_path: Union[str, Path]):
         matched = False
         if self.base_path:
-            rel_path = str(Path(abs_path).resolve().relative_to(self.base_path))
+            rel_path = str(_normalize_path(abs_path).relative_to(self.base_path))
         else:
-            rel_path = str(Path(abs_path))
+            rel_path = str(_normalize_path(abs_path))
         # Path() strips the trailing slash, so we need to preserve it
         # in case of directory-only negation
         if self.negation and type(abs_path) == str and abs_path[-1] == '/':
@@ -208,3 +208,13 @@ def fnmatch_pathname_to_regex(
     else:
         res.append('($|\\/)')
     return ''.join(res)
+
+
+def _normalize_path(path: Union[str, Path]) -> Path:
+    """Normalize a path without resolving symlinks.
+
+    This is equivalent to `Path.resolve()` except that it does not resolve symlinks.
+    Note that this simplifies paths by removing double slashes, `..`, `.` etc. like
+    `Path.resolve()` does.
+    """
+    return Path(abspath(path))

tests.py

@@ -1,5 +1,6 @@
 from unittest.mock import patch, mock_open
 from pathlib import Path
+from tempfile import TemporaryDirectory
 
 from gitignore_parser import parse_gitignore
 
@@ -178,10 +179,32 @@ def test_slash_in_range_does_not_match_dirs(self):
         self.assertFalse(matches('/home/michael/abc/def'))
         self.assertFalse(matches('/home/michael/abcXYZdef'))
 
+    def test_symlink_to_another_directory(self):
+        """Test the behavior of a symlink to another directory.
+
+        The issue https://github.com/mherrmann/gitignore_parser/issues/29 describes how
+        a symlink to another directory caused an exception to be raised during matching.
+
+        This test ensures that the issue is now fixed.
+        """
+        with TemporaryDirectory() as project_dir, TemporaryDirectory() as another_dir:
+            matches = _parse_gitignore_string('link', fake_base_dir=project_dir)
+
+            # Create a symlink to another directory.
+            link = Path(project_dir, 'link')
+            target = Path(another_dir, 'target')
+            link.symlink_to(target)
+
+            # Check the intended behavior according to
+            # https://git-scm.com/docs/gitignore#_notes:
+            # Symbolic links are not followed and are matched as if they were regular
+            # files.
+            self.assertTrue(matches(link))
+
 def _parse_gitignore_string(data: str, fake_base_dir: str = None):
     with patch('builtins.open', mock_open(read_data=data)):
         success = parse_gitignore(f'{fake_base_dir}/.gitignore', fake_base_dir)
         return success
 
 if __name__ == '__main__':
-    main()
+    main()