Problem: TOP_DIR_x are global

Solution: use functools.partial to avoid the need for global vars.

Author: gotcha

pyannotate_runtime/collect_types.py

@@ -703,11 +703,6 @@ def type_consumer():
 
 running = False
 
-TOP_DIR = os.path.join(os.getcwd(), '')     # current dir with trailing slash
-TOP_DIR_DOT = os.path.join(TOP_DIR, '.')
-TOP_DIR_LEN = len(TOP_DIR)
-
-
 def _make_sampling_sequence(n):
     # type: (int) -> List[int]
     """
@@ -784,30 +779,36 @@ def start():
     sampling_counters.clear()
 
 
-def default_filter_filename(filename):
-    # type: (Optional[str]) -> Optional[str]
+def default_filter_filename(top_dir, filename):
+    # type: (str, Optional[str]) -> Optional[str]
     """Default filter for filenames.
 
     Returns either a normalized filename or None.
     You can pass your own filter to init_types_collection().
     """
     if filename is None:
         return None
-    elif filename.startswith(TOP_DIR):
-        if filename.startswith(TOP_DIR_DOT):
+    elif filename.startswith(top_dir):
+        top_dir_dot = os.path.join(top_dir, '.')
+        if filename.startswith(top_dir_dot):
             # Skip subdirectories starting with dot (e.g. .vagrant).
             return None
         else:
             # Strip current directory and following slashes.
-            return filename[TOP_DIR_LEN:].lstrip(os.sep)
+            return filename[len(top_dir):].lstrip(os.sep)
     elif filename.startswith(os.sep):
         # Skip absolute paths not under current directory.
         return None
     else:
         return filename
 
+from functools import partial
+
+cwd_default_filter_filename = partial(default_filter_filename,
+        os.path.join(os.getcwd()))
+
 
-_filter_filename = default_filter_filename  # type: Callable[[Optional[str]], Optional[str]]
+_filter_filename = cwd_default_filter_filename  # type: Callable[[Optional[str]], Optional[str]]
 
 
 if sys.version_info[0] == 2: