Made env generation polymorphic

tests/util_test.py

@@ -0,0 +1,29 @@
+
+import pytest
+import time
+
+from pre_commit.util import cached_property
+
+
+@pytest.fixture
+def class_with_cached_property():
+    class Foo(object):
+        @cached_property
+        def foo(self):
+            return "Foo" + str(time.time())
+
+    return Foo
+
+
+def test_cached_property(class_with_cached_property):
+    instance = class_with_cached_property()
+    val = instance.foo
+    val2 = instance.foo
+    assert val is val2
+
+
+def test_unbound_cached_property(class_with_cached_property):
+    # Make sure we don't blow up when accessing the property unbound
+    prop = class_with_cached_property.foo
+    assert isinstance(prop, cached_property)
+