Fix tab completion (#2055)

* Fix tab completion

* Fix tests

* Always install the monkeypatch

* Update release note

* Apply suggestion from @leofang

Co-authored-by: Leo Fang <leof@nvidia.com>

* Fix test

* Fix tests hanging on Windows

---------

Co-authored-by: Leo Fang <leof@nvidia.com>

Author: mdboom

cuda_core/cuda/core/__init__.py

@@ -28,6 +28,46 @@ def _import_versioned_module():
 del _import_versioned_module
 
 
+def _patch_rlcompleter_for_cython_properties():
+    # TODO: This can be removed when Python 3.13 is our minimum-supported version:
+    #   https://github.com/python/cpython/pull/149577
+
+    # Cython @property on cdef class compiles to a C-level getset_descriptor,
+    # which rlcompleter's narrow isinstance(..., property) check misses; the
+    # fallback getattr() then invokes the descriptor and any non-AttributeError
+    # it raises kills tab completion. Extend that isinstance check to also
+    # match getset_descriptor / member_descriptor. Only installed in
+    # interactive mode so library users running scripts see no global
+    # rlcompleter side effect.
+    import os
+
+    if int(os.environ.get("CUDA_CORE_DONT_FIX_TAB_COMPLETION", "0")):
+        # Explicit opt-out for users who don't want the global rlcompleter
+        # side effect, even in an interactive session.
+        return
+
+    import rlcompleter
+    from types import GetSetDescriptorType, MemberDescriptorType
+
+    # This works by overriding the `property` built-in with a custom subclass of
+    # property, but only in the rlcompleter module.  This subclass overrides the
+    # `__instancecheck__` method to also return True for getset_descriptor and
+    # member_descriptor types, which are what Cython uses for properties on cdef
+    # classes.
+    class _PatchedPropMeta(type):
+        def __instancecheck__(cls, inst):
+            return isinstance(inst, (property, GetSetDescriptorType, MemberDescriptorType))
+
+    class _PatchedProperty(metaclass=_PatchedPropMeta):
+        pass
+
+    rlcompleter.property = _PatchedProperty
+
+
+_patch_rlcompleter_for_cython_properties()
+del _patch_rlcompleter_for_cython_properties
+
+
 from cuda.core import checkpoint, system, utils
 from cuda.core._context import Context, ContextOptions
 from cuda.core._device import Device

cuda_core/docs/source/release/1.0.0-notes.rst

@@ -357,3 +357,12 @@ Fixes and enhancements
   package size. Debug builds are now supported via
   ``--config-settings=debug=true``.
   (`#1890 <https://github.com/NVIDIA/cuda-python/pull/1890>`__)
+- Fixed tab completion silently breaking in the CPython REPL on some
+  ``cuda.core`` objects (for example, hitting Tab after ``mr.`` for a
+  ``DeviceMemoryResource`` would produce no suggestions due to a CPython
+  limitation interacting with Cython properties). When ``cuda.core`` is
+  imported in an interactive session it now applies a small patch to the
+  standard library REPL completer so tab completion works as expected.
+  If you would rather not have ``cuda.core`` modify the REPL completer, set
+  ``CUDA_CORE_DONT_FIX_TAB_COMPLETION=1`` to opt out.
+  (`#2053 <https://github.com/NVIDIA/cuda-python/issues/2053>`__)

cuda_core/tests/test_rlcompleter_patch.py

@@ -0,0 +1,106 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+"""
+Tests for the rlcompleter monkeypatch installed by `cuda.core` in interactive
+sessions.
+
+These tests reproduce the original bug report (NVIDIA/cuda-python#2053): tab
+completion on a non-IPC-enabled DeviceMemoryResource crashes because the
+Cython @property `allocation_handle` raises RuntimeError, and rlcompleter's
+narrow `isinstance(..., property)` check misses C-level getset_descriptor
+types and therefore invokes the descriptor.
+
+The patch only installs in interactive mode, so each scenario is exercised in
+a fresh subprocess with a controlled combination of `PYTHONINSPECT` and
+`CUDA_CORE_DONT_FIX_TAB_COMPLETION`.
+"""
+
+import os
+import subprocess
+import sys
+import tempfile
+import textwrap
+
+import pytest
+
+from cuda.core import Device
+
+
+def _gpu_with_mempool_or_skip():
+    """Skip when no GPU or no mempool support — test mirrors the bug repro."""
+    if len(Device.get_all_devices()) == 0:
+        pytest.skip("Test requires a CUDA device")
+    dev = Device(0)
+    if not dev.properties.memory_pools_supported:
+        pytest.skip("Device 0 does not support mempool operations")
+
+
+# Probe script: reproduces the bug-report repro literally, then runs
+# rlcompleter against `mr` and reports the outcome.
+_PROBE_SCRIPT = textwrap.dedent("""
+    import rlcompleter
+    from cuda.core import Device, DeviceMemoryResource
+
+    dev = Device(0)
+    dev.set_current()
+    mr = DeviceMemoryResource(dev)
+    assert not mr.is_ipc_enabled, "test setup: mr should not be IPC-enabled"
+
+    completer = rlcompleter.Completer({"mr": mr})
+    try:
+        matches = completer.attr_matches("mr.")
+    except Exception as exc:
+        print(f"crash: {type(exc).__name__}: {exc}")
+    else:
+        print(f"ok: {len(matches)} matches")
+        print(f"allocation_handle: {'mr.allocation_handle' in matches}")
+""")
+
+
+def _run_probe(*, pythoninspect: bool, opt_out: bool = False) -> subprocess.CompletedProcess:
+    env = os.environ.copy()
+    # Don't let parent-environment values bleed into the subprocess.
+    env.pop("CUDA_CORE_DONT_FIX_TAB_COMPLETION", None)
+    # Drop PYTHONPATH so the subprocess can't find a source-tree cuda.core
+    # via an inherited path entry; we want it to import the installed wheel.
+    env.pop("PYTHONPATH", None)
+    if opt_out:
+        env["CUDA_CORE_DONT_FIX_TAB_COMPLETION"] = "1"
+    # `python -c` puts the parent's CWD at the head of sys.path. If pytest is
+    # run from `cuda_core/` (which contains a `cuda/core/` source tree), that
+    # source tree shadows the installed package. Run the subprocess from a
+    # neutral temp dir to avoid this.
+    with tempfile.TemporaryDirectory() as tmpdir:
+        return subprocess.run(  # noqa: S603
+            [sys.executable, "-c", _PROBE_SCRIPT],
+            capture_output=True,
+            text=True,
+            env=env,
+            check=False,
+            # PYTHONINSPECT keeps the interpreter alive after `-c`; close stdin
+            # so the implicit REPL exits immediately.
+            stdin=subprocess.DEVNULL,
+            cwd=tmpdir,
+        )
+
+
+def test_patched_completion_succeeds_on_non_ipc_resource():
+    """With the patch installed (PYTHONINSPECT=1), tab completion must not
+    crash and `mr.allocation_handle` must appear in the matches."""
+    _gpu_with_mempool_or_skip()
+
+    result = _run_probe(pythoninspect=True)
+    assert result.returncode == 0, f"stderr: {result.stderr}\nstdout: {result.stdout}"
+    assert result.stdout.startswith("ok:"), result.stdout
+    assert "allocation_handle: True" in result.stdout, result.stdout
+
+
+def test_opt_out_env_var_disables_patch_even_when_interactive():
+    """`CUDA_CORE_DONT_FIX_TAB_COMPLETION=1` must short-circuit before the
+    interactive check, so the bug reproduces again even under PYTHONINSPECT."""
+    _gpu_with_mempool_or_skip()
+
+    result = _run_probe(pythoninspect=True, opt_out=True)
+    assert result.returncode == 0, f"stderr: {result.stderr}\nstdout: {result.stdout}"
+    assert "crash: RuntimeError" in result.stdout, result.stdout