Ensure disp_class cannot be None in DispatchWithEvents and WithEvents

com/win32com/client/CLSIDToClass.py

@@ -17,7 +17,9 @@
 Access.
 """
 
-mapCLSIDToClass = {}
+from __future__ import annotations
+
+mapCLSIDToClass: dict[str, type] = {}
 
 
 def RegisterCLSID(clsid, pythonClass):

com/win32com/client/__init__.py

@@ -5,6 +5,7 @@
 # Note that if the unknown dispatch object then returns a known
 # dispatch object, the known class will be used.  This contrasts
 # with dynamic.Dispatch behaviour, where dynamic objects are always used.
+from __future__ import annotations
 
 import sys
 from itertools import chain
@@ -263,7 +264,39 @@ def __setattr__(self, attr, val):
         setattr(self._obj_, attr, val)
 
 
-def DispatchWithEvents(clsid, user_event_class):
+def __get_disp_and_event_classes(dispatch):
+    # Create/Get the object.
+    disp = Dispatch(dispatch)
+
+    if disp.__class__.__dict__.get("CLSID"):
+        return disp.__class__
+
+    # Eeek - no makepy support - try and build it.
+    error_msg = "This COM object can not automate the makepy process - please run makepy manually for this object"
+    try:
+        ti = disp._oleobj_.GetTypeInfo()
+        disp_clsid = ti.GetTypeAttr()[0]
+        tlb, index = ti.GetContainingTypeLib()
+        tla = tlb.GetLibAttr()
+        gencache.EnsureModule(tla[0], tla[1], tla[3], tla[4], bValidateFile=0)
+        # Get the class from the module.
+        disp_class = gencache.GetClassForProgID(str(disp_clsid))
+    except pythoncom.com_error as error:
+        raise TypeError(error_msg) from error
+
+    if disp_class is None:
+        raise TypeError(error_msg)
+    # Get the clsid
+    clsid = disp_class.CLSID
+    # Create a new class that derives from 2 classes:
+    # the event sink class and the user class.
+    events_class = getevents(clsid)
+    if events_class is None:
+        raise ValueError("This COM object does not support events.")
+    return disp, disp_class, events_class
+
+
+def DispatchWithEvents(clsid, user_event_class) -> EventsProxy:
     """Create a COM object that can fire events to a user defined class.
     clsid -- The ProgID or CLSID of the object to create.
     user_event_class -- A Python class object that responds to the events.
@@ -302,39 +335,14 @@ class object that derives from three classes:
     Visible changed: 1
     >>>
     """
-    # Create/Get the object.
-    disp = Dispatch(clsid)
-    if not disp.__class__.__dict__.get(
-        "CLSID"
-    ):  # Eeek - no makepy support - try and build it.
-        try:
-            ti = disp._oleobj_.GetTypeInfo()
-            disp_clsid = ti.GetTypeAttr()[0]
-            tlb, index = ti.GetContainingTypeLib()
-            tla = tlb.GetLibAttr()
-            gencache.EnsureModule(tla[0], tla[1], tla[3], tla[4], bValidateFile=0)
-            # Get the class from the module.
-            disp_class = gencache.GetClassForProgID(str(disp_clsid))
-        except pythoncom.com_error:
-            raise TypeError(
-                "This COM object can not automate the makepy process - please run makepy manually for this object"
-            )
-    else:
-        disp_class = disp.__class__
-    # If the clsid was an object, get the clsid
-    clsid = disp_class.CLSID
-    # Create a new class that derives from 3 classes - the dispatch class, the event sink class and the user class.
-    events_class = getevents(clsid)
-    if events_class is None:
-        raise ValueError("This COM object does not support events.")
+    disp, disp_class, events_class = __get_disp_and_event_classes(clsid)
     result_class = type(
         "COMEventClass",
         (disp_class, events_class, user_event_class),
         {"__setattr__": _event_setattr_},
     )
-    instance = result_class(
-        disp._oleobj_
-    )  # This only calls the first base class __init__.
+    # This only calls the first base class __init__.
+    instance = result_class(disp._oleobj_)
     events_class.__init__(instance, instance)
     if hasattr(user_event_class, "__init__"):
         user_event_class.__init__(instance)
@@ -365,33 +373,14 @@ def WithEvents(disp, user_event_class):
     This is mainly useful where using DispatchWithEvents causes
     circular reference problems that the simple proxy doesn't deal with
     """
-    disp = Dispatch(disp)
-    if not disp.__class__.__dict__.get(
-        "CLSID"
-    ):  # Eeek - no makepy support - try and build it.
-        try:
-            ti = disp._oleobj_.GetTypeInfo()
-            disp_clsid = ti.GetTypeAttr()[0]
-            tlb, index = ti.GetContainingTypeLib()
-            tla = tlb.GetLibAttr()
-            gencache.EnsureModule(tla[0], tla[1], tla[3], tla[4], bValidateFile=0)
-            # Get the class from the module.
-            disp_class = gencache.GetClassForProgID(str(disp_clsid))
-        except pythoncom.com_error:
-            raise TypeError(
-                "This COM object can not automate the makepy process - please run makepy manually for this object"
-            )
-    else:
-        disp_class = disp.__class__
-    # Get the clsid
-    clsid = disp_class.CLSID
-    # Create a new class that derives from 2 classes - the event sink
-    # class and the user class.
-    events_class = getevents(clsid)
-    if events_class is None:
-        raise ValueError("This COM object does not support events.")
-    result_class = type("COMEventClass", (events_class, user_event_class), {})
-    instance = result_class(disp)  # This only calls the first base class __init__.
+    disp, disp_class, events_class = __get_disp_and_event_classes(disp)
+    result_class = type(
+        "COMEventClass",
+        (events_class, user_event_class),
+        {},
+    )
+    # This only calls the first base class __init__.
+    instance = result_class(disp)
     if hasattr(user_event_class, "__init__"):
         user_event_class.__init__(instance)
     return instance
@@ -556,7 +545,7 @@ def _ApplyTypes_(self, dispid, wFlags, retType, argTypes, user, resultCLSID, *ar
     def __getattr__(self, attr):
         args = self._prop_map_get_.get(attr)
         if args is None:
-            raise AttributeError(f"'{repr(self)}' object has no attribute '{attr}'")
+            raise AttributeError(f"'{self!r}' object has no attribute '{attr}'")
         return self._ApplyTypes_(*args)
 
     def __setattr__(self, attr, value):
@@ -566,7 +555,7 @@ def __setattr__(self, attr, value):
         try:
             args, defArgs = self._prop_map_put_[attr]
         except KeyError:
-            raise AttributeError(f"'{repr(self)}' object has no attribute '{attr}'")
+            raise AttributeError(f"'{self!r}' object has no attribute '{attr}'")
         self._oleobj_.Invoke(*(args + (value,) + defArgs))
 
     def _get_good_single_object_(self, obj, obUserName=None, resultCLSID=None):