Avoid automatically patching classmethods

Author: hasier

aws_xray_sdk/core/patcher.py

@@ -6,7 +6,8 @@
 import re
 import sys
 import wrapt
-from .utils.compat import PY2, is_instance_method
+
+from .utils.compat import PY2, is_classmethod, is_instance_method
 
 log = logging.getLogger(__name__)
 
@@ -136,7 +137,13 @@ def _patch_class(module, cls):
     for member_name, member in inspect.getmembers(cls, inspect.ismethod):
         if member.__module__ == module.__name__:
             # Only patch methods of the class defined in the module, ignore other modules
-            _patch_func(cls, member_name, member)
+            if is_classmethod(member):
+                # classmethods are internally generated through descriptors. The classmethod
+                # decorator must be the last applied, so we cannot apply another one on top
+                log.warning('Cannot automatically patch classmethod %s.%s, '
+                            'please apply decorator manually', cls.__name__, member_name)
+            else:
+                _patch_func(cls, member_name, member)
 
     for member_name, member in inspect.getmembers(cls, inspect.isfunction):
         if member.__module__ == module.__name__:

aws_xray_sdk/core/utils/compat.py

@@ -13,6 +13,10 @@
     string_types = str
 
 
+def is_classmethod(func):
+    return getattr(func, '__self__', None) is not None
+
+
 def is_instance_method(parent_class, func_name, func):
     try:
         func_from_dict = parent_class.__dict__[func_name]
@@ -24,4 +28,4 @@ def is_instance_method(parent_class, func_name, func):
         else:
             return True
 
-    return getattr(func, '__self__', None) is None and not isinstance(func_from_dict, staticmethod)
+    return not is_classmethod(func) and not isinstance(func_from_dict, staticmethod)

tests/mock_module/mock_submodule/mock_subfile.py

@@ -19,6 +19,7 @@ def mock_method(self):
 
     @classmethod
     def mock_classmethod(cls):
+        # Should not be automatically patched
         pass
 
     @staticmethod

tests/test_patcher.py

@@ -105,16 +105,15 @@ def test_external_module():
 
     _call_all_mock_functions()
 
-    assert len(xray_recorder.current_segment().subsegments) == 9
+    assert len(xray_recorder.current_segment().subsegments) == 8
     assert xray_recorder.current_segment().subsegments[0].name == 'mock_subinit'
     assert xray_recorder.current_segment().subsegments[1].name == 'mock_subfunc'
     assert xray_recorder.current_segment().subsegments[2].name == 'mock_no_doublepatch'  # Should appear only once
-    assert xray_recorder.current_segment().subsegments[3].name == 'mock_classmethod'
-    assert xray_recorder.current_segment().subsegments[4].name == 'mock_staticmethod'
-    assert xray_recorder.current_segment().subsegments[5].name == 'MockClass.__init__'
-    assert xray_recorder.current_segment().subsegments[6].name == 'mock_method'
-    assert xray_recorder.current_segment().subsegments[7].name == 'MockSubclass.__init__'
-    assert xray_recorder.current_segment().subsegments[8].name == 'mock_submethod'
+    assert xray_recorder.current_segment().subsegments[3].name == 'mock_staticmethod'
+    assert xray_recorder.current_segment().subsegments[4].name == 'MockClass.__init__'
+    assert xray_recorder.current_segment().subsegments[5].name == 'mock_method'
+    assert xray_recorder.current_segment().subsegments[6].name == 'MockSubclass.__init__'
+    assert xray_recorder.current_segment().subsegments[7].name == 'mock_submethod'
 
 
 def test_external_submodules_full():
@@ -126,18 +125,17 @@ def test_external_submodules_full():
 
     _call_all_mock_functions()
 
-    assert len(xray_recorder.current_segment().subsegments) == 11
+    assert len(xray_recorder.current_segment().subsegments) == 10
     assert xray_recorder.current_segment().subsegments[0].name == 'mock_init'
     assert xray_recorder.current_segment().subsegments[1].name == 'mock_subinit'
     assert xray_recorder.current_segment().subsegments[2].name == 'mock_func'
     assert xray_recorder.current_segment().subsegments[3].name == 'mock_subfunc'
     assert xray_recorder.current_segment().subsegments[4].name == 'mock_no_doublepatch'
-    assert xray_recorder.current_segment().subsegments[5].name == 'mock_classmethod'
-    assert xray_recorder.current_segment().subsegments[6].name == 'mock_staticmethod'
-    assert xray_recorder.current_segment().subsegments[7].name == 'MockClass.__init__'
-    assert xray_recorder.current_segment().subsegments[8].name == 'mock_method'
-    assert xray_recorder.current_segment().subsegments[9].name == 'MockSubclass.__init__'
-    assert xray_recorder.current_segment().subsegments[10].name == 'mock_submethod'
+    assert xray_recorder.current_segment().subsegments[5].name == 'mock_staticmethod'
+    assert xray_recorder.current_segment().subsegments[6].name == 'MockClass.__init__'
+    assert xray_recorder.current_segment().subsegments[7].name == 'mock_method'
+    assert xray_recorder.current_segment().subsegments[8].name == 'MockSubclass.__init__'
+    assert xray_recorder.current_segment().subsegments[9].name == 'mock_submethod'
 
 
 def test_external_submodules_ignores_file():
@@ -149,17 +147,16 @@ def test_external_submodules_ignores_file():
 
     _call_all_mock_functions()
 
-    assert len(xray_recorder.current_segment().subsegments) == 10
+    assert len(xray_recorder.current_segment().subsegments) == 9
     assert xray_recorder.current_segment().subsegments[0].name == 'mock_init'
     assert xray_recorder.current_segment().subsegments[1].name == 'mock_subinit'
     assert xray_recorder.current_segment().subsegments[2].name == 'mock_subfunc'
     assert xray_recorder.current_segment().subsegments[3].name == 'mock_no_doublepatch'
-    assert xray_recorder.current_segment().subsegments[4].name == 'mock_classmethod'
-    assert xray_recorder.current_segment().subsegments[5].name == 'mock_staticmethod'
-    assert xray_recorder.current_segment().subsegments[6].name == 'MockClass.__init__'
-    assert xray_recorder.current_segment().subsegments[7].name == 'mock_method'
-    assert xray_recorder.current_segment().subsegments[8].name == 'MockSubclass.__init__'
-    assert xray_recorder.current_segment().subsegments[9].name == 'mock_submethod'
+    assert xray_recorder.current_segment().subsegments[4].name == 'mock_staticmethod'
+    assert xray_recorder.current_segment().subsegments[5].name == 'MockClass.__init__'
+    assert xray_recorder.current_segment().subsegments[6].name == 'mock_method'
+    assert xray_recorder.current_segment().subsegments[7].name == 'MockSubclass.__init__'
+    assert xray_recorder.current_segment().subsegments[8].name == 'mock_submethod'
 
 
 def test_external_submodules_ignores_module():