Support environment markers in *_requires, via WorkingSet.

2 files changed, 9 insertions, 0 deletions

diff --git a/pkg_resources/__init__.py b/pkg_resources/__init__.py
index 0534f54f..bb69b607 100644
--- a/pkg_resources/__init__.py
+++ b/pkg_resources/__init__.py
@@ -809,6 +809,10 @@ class WorkingSet(object):
             if req in processed:
                 # Ignore cyclic or redundant dependencies
                 continue
+            # If the req has a marker, evaluate it -- skipping the req if
+            # it evaluates to False.
+            if req.marker and not req.marker.evaluate():
+                continue
             dist = best.get(req.key)
             if dist is None:
                 # Find the best distribution and add it to the map
diff --git a/pkg_resources/tests/test_resources.py b/pkg_resources/tests/test_resources.py
index 1444b9ba..1d3d5315 100644
--- a/pkg_resources/tests/test_resources.py
+++ b/pkg_resources/tests/test_resources.py
@@ -182,6 +182,11 @@ class TestDistro:
         msg = 'Foo 0.9 is installed but Foo==1.2 is required'
         assert vc.value.report() == msg
 
+        ws = WorkingSet([]) # reset
+        # Environment markers are evaluated at resolution time
+        res = ws.resolve(parse_requirements("Foo;python_version<'2'"), ad)
+        assert list(res) == []
+
     def testDistroDependsOptions(self):
         d = self.distRequires("""
             Twisted>=1.5