First stab at adding a generic __new__

This just adds some machinery with just enough
support in data structures to be able to instantiate
classes without keyword arguments.

TODO:
- Add machinery for framework bindings
- Add support code to _transform (automaticly
  initialize the data structure based on init methods)
- Add tests
- Finally: update framework bindings

pyobjc-core/Lib/objc/__init__.py

@@ -44,6 +44,7 @@ def _update(g):
 from . import _callable_docstr  # noqa: F401, F403, E402
 from . import _pycoder  # noqa: F401, F403, E402
 from ._informal_protocol import *  # noqa: F401, F403, E402
+from . import _new  # noqa: E402
 
 
 # Helper function for new-style metadata modules
@@ -83,3 +84,8 @@ def __enter__(self):
 
     def __exit__(self, exc_type, value, tp):
         del self._pool
+
+
+_new.NEW_MAP[lookUpClass("NSObject")] = {  # noqa: F405
+    (): "init",
+}

pyobjc-core/Lib/objc/_convenience.py

@@ -13,6 +13,7 @@
     selector,
 )
 import PyObjCTools.KeyValueCoding as kvc
+from objc._new import _make_new
 
 __all__ = ("addConvenienceForClass", "registerABCForClass")
 
@@ -54,6 +55,9 @@ class name to a list of Python method names and implementation.
 
     Matching entries from both mappings are added to the 'type_dict'.
     """
+    if type_dict.get("__new__") is None:
+        type_dict["__new__"] = _make_new(cls)
+
     for nm, value in CLASS_METHODS.get(cls.__name__, ()):
         type_dict[nm] = value
 

pyobjc-core/Lib/objc/_new.py

@@ -0,0 +1,54 @@
+"""
+Implementation of `__new__` for arbitrary Cocoa classes
+"""
+
+__all__ = ()
+
+NEW_MAP = {}
+UNSET = object()
+
+# XXX: Need to find a way to dynamically set the docstring
+
+
+def _make_new(cls):
+    def __new__(cls, **kwds):
+        """
+        Generic implementation for Objective-C `__new__`.
+        """
+        # XXX: should this sort the keywords?
+        key = tuple(kwds.keys())
+
+        for c in cls.__mro__:
+            new_map = NEW_MAP.get(c, UNSET)
+            if new_map is UNSET:
+                continue
+
+            name = new_map.get(key, UNSET)
+            if name is UNSET:
+                continue
+
+            if name is None:
+                if key:
+                    raise TypeError(
+                        f"{cls.__name__}() does not support keyword arguments {', '.join(repr(k) for k in key)}"
+                    )
+                else:
+                    raise TypeError(f"{cls.__name__}() requires keyword arguments")
+
+            if name.startswith("init") and len(name) == 4 or name[4].isupper():
+                return getattr(cls.alloc(), name)(**kwds)
+
+            else:
+                return getattr(cls, name)(**kwds)
+
+        if key:
+            raise TypeError(
+                f"{cls.__name__}() does not support keyword arguments {', '.join(repr(k) for k in key)}"
+            )
+        else:
+            raise TypeError(f"{cls.__name__}() requires keyword arguments")
+
+    __new__.__name__ = cls.__name__ + ".__new__"
+    __new__.__qualname__ = cls.__name__ + ".__new__"
+    __new__.__module__ = cls.__module__
+    return __new__