Always inject extra into the environment when evaluating markers. Fixes #544.

CHANGES.rst

@@ -2,6 +2,12 @@
 CHANGES
 =======
 
+v20.8.1
+-------
+
+* Issue #544: Fix issue with extra environment marker
+  processing in WorkingSet due to refactor in v20.7.0.
+
 v20.8.0
 -------
 

pkg_resources/__init__.py

@@ -988,9 +988,9 @@ class _ReqExtras(dict):
         """
         extra_evals = (
             req.marker.evaluate({'extra': extra})
-            for extra in self.get(req, ())
+            for extra in self.get(req, ()) + (None,)
         )
-        return not req.marker or any(extra_evals) or req.marker.evaluate()
+        return not req.marker or any(extra_evals)
 
 
 class Environment(object):

pkg_resources/tests/test_resources.py

@@ -189,7 +189,7 @@ class TestDistro:
     def test_environment_marker_evaluation_called(self):
         """
         If one package foo requires bar without any extras,
-        markers should pass for bar.
+        markers should pass for bar without extras.
         """
         parent_req, = parse_requirements("foo")
         req, = parse_requirements("bar;python_version>='2'")
@@ -201,14 +201,6 @@ class TestDistro:
         req_extras = pkg_resources._ReqExtras({req: parent_req.extras})
         assert req_extras.markers_pass(req)
 
-        # extra should not be present in the marker namespace if
-        # no markers were supplied
-        parent_req, = parse_requirements("foo")
-        req, = parse_requirements("bar;extra==''")
-        req_extras = pkg_resources._ReqExtras({req: parent_req.extras})
-        with pytest.raises(packaging.markers.UndefinedEnvironmentName):
-            req_extras.markers_pass(req)
-
     def test_marker_evaluation_with_extras(self):
         """Extras are also evaluated as markers at resolution time."""
         ad = pkg_resources.Environment([])