Change __cuda_stream__ from attribute to method

cuda_core/cuda/core/experimental/_stream.py

@@ -5,6 +5,7 @@
 from __future__ import annotations
 
 import os
+import warnings
 import weakref
 from dataclasses import dataclass
 from typing import TYPE_CHECKING, Optional, Tuple, Union
@@ -87,9 +88,19 @@ def _init(obj=None, *, options: Optional[StreamOptions] = None):
         if obj is not None and options is not None:
             raise ValueError("obj and options cannot be both specified")
         if obj is not None:
-            if not hasattr(obj, "__cuda_stream__"):
-                raise ValueError
-            info = obj.__cuda_stream__
+            try:
+                info = obj.__cuda_stream__()
+            except AttributeError as e:
+                raise TypeError(f"{type(obj)} object does not have a '__cuda_stream__' method") from e
+            except TypeError:
+                info = obj.__cuda_stream__
+                warnings.simplefilter("once", DeprecationWarning)
+                warnings.warn(
+                    "Implementing __cuda_stream__ as an attribute is deprecated; it must be implemented as a method",
+                    stacklevel=3,
+                    category=DeprecationWarning,
+                )
+
             assert info[0] == 0
             self._mnff.handle = cuda.CUstream(info[1])
             # TODO: check if obj is created under the current context/device
@@ -132,7 +143,6 @@ def close(self):
         """
         self._mnff.close()
 
-    @property
     def __cuda_stream__(self) -> Tuple[int, int]:
         """Return an instance of a __cuda_stream__ protocol."""
         return (0, self.handle)
@@ -279,7 +289,6 @@ def from_handle(handle: int) -> Stream:
         """
 
         class _stream_holder:
-            @property
             def __cuda_stream__(self):
                 return (0, handle)
 

cuda_core/docs/source/interoperability.rst

@@ -34,14 +34,13 @@ exposing their own stream types.
 
 To address this issue, we propose the ``__cuda_stream__`` protocol (currently version
 0) as follows: For any Python objects that are meant to be interpreted as a stream, they
-should add a ``__cuda_stream__`` attribute that returns a 2-tuple: The version number
+should add a ``__cuda_stream__`` method that returns a 2-tuple: The version number
 (``0``) and the address of ``cudaStream_t`` (both as Python `int`):
 
 .. code-block:: python
 
    class MyStream:
 
-       @property
        def __cuda_stream__(self):
            return (0, self.ptr)
 

cuda_core/docs/source/release.md

@@ -5,6 +5,7 @@
 maxdepth: 3
 ---
 
+    0.2.0 <release/0.2.0-notes>
     0.1.1 <release/0.1.1-notes>
     0.1.0 <release/0.1.0-notes>
 

cuda_core/docs/source/release/0.2.0-notes.rst

@@ -0,0 +1,7 @@
+``cuda.core`` v0.2.0 Release notes
+==================================
+
+Breaking changes
+----------------
+
+- Change ``__cuda_stream__`` from attribute to method

cuda_core/examples/simple_multi_gpu_example.py

@@ -81,7 +81,6 @@ class StreamAdaptor:
     def __init__(self, obj):
         self.obj = obj
 
-    @property
     def __cuda_stream__(self):
         # Note: CuPy streams have a .ptr attribute
         return (0, self.obj.ptr)