fixes pytest-dev#2208 by introducing a iteration limit

CHANGELOG.rst

@@ -41,6 +41,10 @@ Changes
 * fix `#2013`_: turn RecordedWarning into namedtupe,
   to give it a comprehensible repr while preventing unwarranted modification
 
+* fix `#2208`_: ensure a iteration limit for _pytest.compat.get_real_func.
+  Thanks `@RonnyPfannschmidt`_ for the Report and PR
+
+
 .. _@davidszotten: https://github.com/davidszotten
 .. _@fushi: https://github.com/fushi
 .. _@mattduck: https://github.com/mattduck
@@ -57,6 +61,7 @@ Changes
 .. _#2101: https://github.com/pytest-dev/pytest/pull/2101
 .. _#2166: https://github.com/pytest-dev/pytest/pull/2166
 .. _#2147: https://github.com/pytest-dev/pytest/issues/2147
+.. _#2208: https://github.com/pytest-dev/pytest/issues/2208
 
 3.0.6.dev0 (unreleased)
 =======================

_pytest/compat.py

@@ -180,8 +180,16 @@ def get_real_func(obj):
     """ gets the real function object of the (possibly) wrapped object by
     functools.wraps or functools.partial.
     """
-    while hasattr(obj, "__wrapped__"):
-        obj = obj.__wrapped__
+    start_obj = obj
+    for i in range(100):
+        new_obj = getattr(obj, '__wrapped__', None)
+        if new_obj is None:
+            break
+        obj = new_obj
+    else:
+        raise ValueError(
+            ("could not find real function of {start}"
+             "\nstopped at {current}").format(start=start_obj, current=obj))
     if isinstance(obj, functools.partial):
         obj = obj.func
     return obj

testing/test_compat.py

@@ -1,7 +1,7 @@
 import sys
 
 import pytest
-from _pytest.compat import is_generator
+from _pytest.compat import is_generator, get_real_func
 
 
 def test_is_generator():
@@ -15,7 +15,30 @@ def foo():
     assert not is_generator(foo)
 
 
-@pytest.mark.skipif(sys.version_info < (3, 4), reason='asyncio available in Python 3.4+')
+def test_real_func_loop_limit():
+
+    class Evil(object):
+        def __init__(self):
+            self.left = 1000
+
+        def __repr__(self):
+            return "<Evil left={left}>".format(left=self.left)
+
+        def __getattr__(self, attr):
+            if not self.left:
+                raise RuntimeError('its over')
+            self.left -= 1
+            return self
+
+    evil = Evil()
+
+    with pytest.raises(ValueError):
+        res = get_real_func(evil)
+        print(res)
+
+
+@pytest.mark.skipif(sys.version_info < (3, 4),
+                    reason='asyncio available in Python 3.4+')
 def test_is_generator_asyncio(testdir):
     testdir.makepyfile("""
         from _pytest.compat import is_generator
@@ -27,12 +50,14 @@ def baz():
         def test_is_generator_asyncio():
             assert not is_generator(baz)
     """)
-    # avoid importing asyncio into pytest's own process, which in turn imports logging (#8)
+    # avoid importing asyncio into pytest's own process,
+    # which in turn imports logging (#8)
     result = testdir.runpytest_subprocess()
     result.stdout.fnmatch_lines(['*1 passed*'])
 
 
-@pytest.mark.skipif(sys.version_info < (3, 5), reason='async syntax available in Python 3.5+')
+@pytest.mark.skipif(sys.version_info < (3, 5),
+                    reason='async syntax available in Python 3.5+')
 def test_is_generator_async_syntax(testdir):
     testdir.makepyfile("""
         from _pytest.compat import is_generator