Merge pull request #1631 from PyCQA/dupe-sys-path

prevent duplicate plugin discovery on misconfigured pythons

Author: asottile

src/flake8/plugins/finder.py

@@ -179,6 +179,8 @@ def _flake8_plugins(
 
 
 def _find_importlib_plugins() -> Generator[Plugin, None, None]:
+ # some misconfigured pythons (RHEL) have things on `sys.path` twice
+ seen = set()
  for dist in importlib_metadata.distributions():
  # assigned to prevent continual reparsing
  eps = dist.entry_points
@@ -190,6 +192,11 @@ def _find_importlib_plugins() -> Generator[Plugin, None, None]:
  # assigned to prevent continual reparsing
  meta = dist.metadata
 
+ if meta["name"] in seen:
+ continue
+ else:
+ seen.add(meta["name"])
+
  if meta["name"] in BANNED_PLUGINS:
  LOG.warning(
  "%s plugin is obsolete in flake8>=%s",

tests/unit/plugins/finder_test.py

@@ -361,6 +361,23 @@ def test_importlib_plugins(
  ]
 
 
+def test_duplicate_dists(flake8_dist):
+ # some poorly packaged pythons put lib and lib64 on sys.path resulting in
+ # duplicates from `importlib.metadata.distributions`
+ with mock.patch.object(
+ importlib_metadata,
+ "distributions",
+ return_value=[
+ flake8_dist,
+ flake8_dist,
+ ],
+ ):
+ ret = list(finder._find_importlib_plugins())
+
+ # we should not have duplicates
+ assert len(ret) == len(set(ret))
+
+
 def test_find_local_plugins_nothing():
  cfg = configparser.RawConfigParser()
  assert set(finder._find_local_plugins(cfg)) == set()