bpo-37047: Refactor AsyncMock setup logic for autospeccing (GH-13574)

Handle late binding and attribute access in unittest.mock.AsyncMock
setup for autospeccing.

Lib/unittest/mock.py

@@ -51,6 +51,13 @@ def _is_async_obj(obj):
         return False
 
 
+def _is_async_func(func):
+    if getattr(func, '__code__', None):
+        return asyncio.iscoroutinefunction(func)
+    else:
+        return False
+
+
 def _is_instance_mock(obj):
     # can't use isinstance on Mock objects because they override __class__
     # The base class for all mocks is NonCallableMock
@@ -225,6 +232,34 @@ def _setup_func(funcopy, mock, sig):
     mock._mock_delegate = funcopy
 
 
+def _setup_async_mock(mock):
+    mock._is_coroutine = asyncio.coroutines._is_coroutine
+    mock.await_count = 0
+    mock.await_args = None
+    mock.await_args_list = _CallList()
+    mock.awaited = _AwaitEvent(mock)
+
+    # Mock is not configured yet so the attributes are set
+    # to a function and then the corresponding mock helper function
+    # is called when the helper is accessed similar to _setup_func.
+    def wrapper(attr, *args, **kwargs):
+        return getattr(mock.mock, attr)(*args, **kwargs)
+
+    for attribute in ('assert_awaited',
+                      'assert_awaited_once',
+                      'assert_awaited_with',
+                      'assert_awaited_once_with',
+                      'assert_any_await',
+                      'assert_has_awaits',
+                      'assert_not_awaited'):
+
+        # setattr(mock, attribute, wrapper) causes late binding
+        # hence attribute will always be the last value in the loop
+        # Use partial(wrapper, attribute) to ensure the attribute is bound
+        # correctly.
+        setattr(mock, attribute, partial(wrapper, attribute))
+
+
 def _is_magic(name):
     return '__%s__' % name[2:-2] == name
 
@@ -2151,7 +2186,7 @@ class AsyncMockMixin(Base):
         """
         self = _mock_self
         if self.await_count != 0:
-            msg = (f"Expected {self._mock_name or 'mock'} to have been awaited once."
+            msg = (f"Expected {self._mock_name or 'mock'} to not have been awaited."
                    f" Awaited {self.await_count} times.")
             raise AssertionError(msg)
 
@@ -2457,10 +2492,7 @@ def create_autospec(spec, spec_set=False, instance=False, _parent=None,
         spec = type(spec)
 
     is_type = isinstance(spec, type)
-    if getattr(spec, '__code__', None):
-        is_async_func = asyncio.iscoroutinefunction(spec)
-    else:
-        is_async_func = False
+    is_async_func = _is_async_func(spec)
     _kwargs = {'spec': spec}
     if spec_set:
         _kwargs = {'spec_set': spec}
@@ -2498,26 +2530,11 @@ def create_autospec(spec, spec_set=False, instance=False, _parent=None,
                  name=_name, **_kwargs)
 
     if isinstance(spec, FunctionTypes):
-        wrapped_mock = mock
         # should only happen at the top level because we don't
         # recurse for functions
         mock = _set_signature(mock, spec)
         if is_async_func:
-            mock._is_coroutine = asyncio.coroutines._is_coroutine
-            mock.await_count = 0
-            mock.await_args = None
-            mock.await_args_list = _CallList()
-
-            for a in ('assert_awaited',
-                      'assert_awaited_once',
-                      'assert_awaited_with',
-                      'assert_awaited_once_with',
-                      'assert_any_await',
-                      'assert_has_awaits',
-                      'assert_not_awaited'):
-                def f(*args, **kwargs):
-                    return getattr(wrapped_mock, a)(*args, **kwargs)
-                setattr(mock, a, f)
+            _setup_async_mock(mock)
     else:
         _check_signature(spec, mock, is_type, instance)