Fix where() so that it works with importlib.resources when available (#…

…123)

certifi/core.py

@@ -9,7 +9,36 @@
 import os
 
 try:
- from importlib.resources import read_text
+ from importlib.resources import path as get_path, read_text
+
+ _CACERT_CTX = None
+ _CACERT_PATH = None
+
+ def where():
+ # This is slightly terrible, but we want to delay extracting the file
+ # in cases where we're inside of a zipimport situation until someone
+ # actually calls where(), but we don't want to re-extract the file
+ # on every call of where(), so we'll do it once then store it in a
+ # global variable.
+ global _CACERT_CTX
+ global _CACERT_PATH
+ if _CACERT_PATH is None:
+ # This is slightly janky, the importlib.resources API wants you to
+ # manage the cleanup of this file, so it doesn't actually return a
+ # path, it returns a context manager that will give you the path
+ # when you enter it and will do any cleanup when you leave it. In
+ # the common case of not needing a temporary file, it will just
+ # return the file system location and the __exit__() is a no-op.
+ #
+ # We also have to hold onto the actual context manager, because
+ # it will do the cleanup whenever it gets garbage collected, so
+ # we will also store that at the global level as well.
+ _CACERT_CTX = get_path("certifi", "cacert.pem")
+ _CACERT_PATH = str(_CACERT_CTX.__enter__())
+
+ return _CACERT_PATH
+
+
 except ImportError:
  # This fallback will work for Python versions prior to 3.7 that lack the
  # importlib.resources module but relies on the existing `where` function
@@ -19,11 +48,12 @@ def read_text(_module, _path, encoding="ascii"):
  with open(where(), "r", encoding=encoding) as data:
  return data.read()
 
+ # If we don't have importlib.resources, then we will just do the old logic
+ # of assuming we're on the filesystem and munge the path directly.
+ def where():
+ f = os.path.dirname(__file__)
 
-def where():
- f = os.path.dirname(__file__)
-
- return os.path.join(f, "cacert.pem")
+ return os.path.join(f, "cacert.pem")
 
 
 def contents():