Verify that a completer function is defined in a CommandSet before

passing it a CommandSet instance.
Search for a CommandSet instance that matches the completer's parent
class type.`

Resolves Issue #967

Renamed isolated_tests directory to tests_isolated for better visual grouping. Added some exception documentation

1 files changed, 30 insertions, 1 deletions

diff --git a/cmd2/utils.py b/cmd2/utils.py
index 5a4fdbf7..39dc6e2b 100644
--- a/cmd2/utils.py
+++ b/cmd2/utils.py
@@ -3,7 +3,9 @@
 
 import collections
 import collections.abc as collections_abc
+import functools
 import glob
+import inspect
 import os
 import re
 import subprocess
@@ -11,7 +13,7 @@ import sys
 import threading
 import unicodedata
 from enum import Enum
-from typing import Any, Callable, Dict, Iterable, List, Optional, TextIO, Union
+from typing import Any, Callable, Dict, Iterable, List, Optional, TextIO, Type, Union
 
 from . import constants
 
@@ -1037,3 +1039,30 @@ def categorize(func: Union[Callable, Iterable[Callable]], category: str) -> None
             setattr(item, constants.CMD_ATTR_HELP_CATEGORY, category)
     else:
         setattr(func, constants.CMD_ATTR_HELP_CATEGORY, category)
+
+
+def get_defining_class(meth: Callable) -> Optional[Type]:
+    """
+    Attempts to resolve the class that defined a method.
+
+    Inspired by implementation published here:
+        https://stackoverflow.com/a/25959545/1956611
+
+    :param meth: method to inspect
+    :return: class type in which the supplied method was defined. None if it couldn't be resolved.
+    """
+    if isinstance(meth, functools.partial):
+        return get_defining_class(meth.func)
+    if inspect.ismethod(meth) or (inspect.isbuiltin(meth)
+                                  and getattr(meth, '__self__') is not None
+                                  and getattr(meth.__self__, '__class__')):
+        for cls in inspect.getmro(meth.__self__.__class__):
+            if meth.__name__ in cls.__dict__:
+                return cls
+        meth = getattr(meth, '__func__', meth)  # fallback to __qualname__ parsing
+    if inspect.isfunction(meth):
+        cls = getattr(inspect.getmodule(meth),
+                      meth.__qualname__.split('.<locals>', 1)[0].rsplit('.', 1)[0])
+        if isinstance(cls, type):
+            return cls
+    return getattr(meth, '__objclass__', None)  # handle special descriptor objects