Always read extras from InstallRequirement.extras
@@ -162,7 +162,7 @@ class Factory(object):
for ireq in ireqs:
specifier &= ireq.req.specifier
hashes |= ireq.hashes(trust_internet=False)
- extras |= ireq.req.extras
+ extras |= frozenset(ireq.extras)
# We use this to ensure that we only yield a single candidate for
# each version (the finder's preferred one for that version). The
