Don't execute class properties when collecting Python test classes

Previously, properties such as in the added test case were triggered
during collection, possibly executing unintended code. Let's skip them
instead.

We should probably skip all custom descriptors, however I am not sure
how to do this cleanly, so for now just skip properties.

Fixes pytest-dev#2234.

AUTHORS

@@ -118,6 +118,7 @@ Piotr Banaszkiewicz
 Punyashloka Biswal
 Quentin Pradet
 Ralf Schmitt
+Ran Benita
 Raphael Pierzina
 Raquel Alegre
 Roberto Polli

CHANGELOG.rst

@@ -3,6 +3,8 @@
 
 *
 
+* Don't trigger execution of class properties in Python test classes during collection (`#2234`_).
+
 * Replace ``raise StopIteration`` usages in the code by simple ``returns`` to finish generators, in accordance to `PEP-479`_ (`#2160`_).
   Thanks `@tgoodlet`_ for the report and `@nicoddemus`_ for the PR.
 
@@ -16,6 +18,8 @@
 
 *
 
+.. _#2234: https://github.com/pytest-dev/pytest/issues/2234
+
 .. _#2160: https://github.com/pytest-dev/pytest/issues/2160
 
 .. _PEP-479: https://www.python.org/dev/peps/pep-0479/

_pytest/fixtures.py

@@ -1068,6 +1068,9 @@ def parsefactories(self, node_or_obj, nodeid=NOTSET, unittest=False):
         self._holderobjseen.add(holderobj)
         autousenames = []
         for name in dir(holderobj):
+            # Skip properties before the following getattr executes them.
+            if isinstance(type(holderobj).__dict__.get(name), property):
+                continue
             obj = getattr(holderobj, name, None)
             # fixture functions have a pytest_funcarg__ prefix (pre-2.3 style)
             # or are "@pytest.fixture" marked

testing/python/collect.py

@@ -166,6 +166,16 @@ def test_issue1579_namedtuple(self, testdir):
             "because it has a __new__ constructor*"
         )
 
+    def test_issue2234_property(self, testdir):
+        testdir.makepyfile("""
+            class TestCase(object):
+                @property
+                def prop(self):
+                    raise NotImplementedError()
+        """)
+        result = testdir.runpytest()
+        assert result.ret == EXIT_NOTESTSCOLLECTED
+
 
 class TestGenerator:
     def test_generative_functions(self, testdir):