Use inspect to properly detect generators. Fixes pytest-dev#2129

_pytest/compat.py

@@ -19,6 +19,12 @@
     # Only available in Python 3.4+ or as a backport
     enum = None
 
+try:
+    import asyncio
+except ImportError:  # pragma: no cover
+    # Only available in Python 3.4+ or as a backport
+    asyncio = None
+
 _PY3 = sys.version_info > (3, 0)
 _PY2 = not _PY3
 
@@ -42,11 +48,10 @@ def _format_args(func):
 
 
 def is_generator(func):
-    try:
-        return _pytest._code.getrawcode(func).co_flags & 32 # generator function
-    except AttributeError: # builtin functions have no bytecode
-        # assume them to not be generators
-        return False
+    genfunc = inspect.isgeneratorfunction(func)
+    if asyncio is not None:
+        return genfunc and not asyncio.iscoroutinefunction(func)
+    return genfunc
 
 
 def getlocation(function, curdir):

testing/conftest.py

@@ -0,0 +1,7 @@
+import sys
+
+collect_ignore = []
+if sys.version_info[0] < 3:
+    collect_ignore.append("test_compat_3.py")
+if sys.version_info < (3, 5):
+    collect_ignore.append("test_compat_35.py")

testing/test_compat.py

@@ -0,0 +1,12 @@
+from _pytest.compat import is_generator
+
+
+def test_is_generator():
+    def zap():
+        yield
+
+    def foo():
+        pass
+
+    assert is_generator(zap)
+    assert not is_generator(foo)

testing/test_compat_3.py

@@ -0,0 +1,15 @@
+import pytest
+from _pytest.compat import is_generator
+try:
+    import asyncio
+except ImportError:
+    asyncio = None
+
+
+@pytest.mark.skipif(asyncio is None, reason='asyncio is not installed')
+def test_is_generator():
+    @asyncio.coroutine
+    def baz():
+        yield from [1,2,3]
+
+    assert not is_generator(baz)

testing/test_compat_35.py

@@ -0,0 +1,12 @@
+from _pytest.compat import is_generator
+
+
+def test_is_generator_py35():
+    async def foo():
+        await foo()
+
+    async def bar():
+        pass
+
+    assert not is_generator(foo)
+    assert not is_generator(bar)