(arrow) branch main updated: GH-47823: [Python] Use PyWeakref_GetRef instead of PyWeakref_GET_OBJECT (Python 3.15) (#48027)

[alenka]

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alenka pushed a commit to branch main
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The following commit(s) were added to refs/heads/main by this push:
     new a15803601f GH-47823: [Python] Use PyWeakref_GetRef instead of 
PyWeakref_GET_OBJECT (Python 3.15) (#48027)
a15803601f is described below

commit a15803601f439b110ba676fa5ba28473e50f50bc
Author: paultiq <104510378+paul...@users.noreply.github.com>
AuthorDate: Wed Nov 19 03:19:01 2025 -0500

    GH-47823: [Python] Use PyWeakref_GetRef instead of PyWeakref_GET_OBJECT 
(Python 3.15) (#48027)
    
    ### Rationale for this change
    
    pyarrow builds fail on CPython 3.15 due to the 3.15's removal of 
PyWeakref_GetObject, used in extension_types.cc. This was deprecated in 3.13. A 
backport is available in the already-vendored 
[pythoncapi_compat](https://github.com/apache/arrow/blob/main/python/pyarrow/src/arrow/python/vendored/pythoncapi_compat.h).
    
    Fixes https://github.com/apache/arrow/issues/47823. To be clear: this fixes 
only the build issue reported in the issue, not "3.15 support".
    
    ### What changes are included in this PR?
    
    Replaces the sole use of PyWeakref_GET_OBJECT with the backported version 
of PyWeakref_GetRef.
    
    This follows the recommendation from [Pending removal in Python 
3.15](https://docs.python.org/3/deprecations/c-api-pending-removal-in-3.15.html)
    > 
[PyWeakref_GetObject()](https://docs.python.org/3/c-api/weakref.html#c.PyWeakref_GetObject)
 and 
[PyWeakref_GET_OBJECT()](https://docs.python.org/3/c-api/weakref.html#c.PyWeakref_GET_OBJECT):
 Use 
[PyWeakref_GetRef()](https://docs.python.org/3/c-api/weakref.html#c.PyWeakref_GetRef)
 instead. The [pythoncapi-compat 
project](https://github.com/python/pythoncapi-compat/) can be used to get 
[PyWeakref_GetRef()](https://docs.python.org/3/c-api/weakref.html#c.PyWeakref_GetRef)
 on Python 3.12 [...]
    
    ### Are these changes tested?
    Build and tested on a local Ubuntu 24.04 build.
    
    ### Are there any user-facing changes?
    No user-facing changes.
    
    * GitHub Issue: #47823
    
    Authored-by: paultiq <104510378+paul...@users.noreply.github.com>
    Signed-off-by: AlenkaF <frim.ale...@gmail.com>
---
 python/pyarrow/src/arrow/python/extension_type.cc | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/python/pyarrow/src/arrow/python/extension_type.cc 
b/python/pyarrow/src/arrow/python/extension_type.cc
index 8439ecf858..8c3f3f1d8d 100644
--- a/python/pyarrow/src/arrow/python/extension_type.cc
+++ b/python/pyarrow/src/arrow/python/extension_type.cc
@@ -22,6 +22,7 @@
 #include "arrow/python/extension_type.h"
 #include "arrow/python/helpers.h"
 #include "arrow/python/pyarrow.h"
+#include "arrow/python/vendored/pythoncapi_compat.h"
 #include "arrow/util/checked_cast.h"
 #include "arrow/util/logging.h"
 
@@ -164,15 +165,18 @@ PyObject* PyExtensionType::GetInstance() const {
     return nullptr;
   }
   ARROW_DCHECK(PyWeakref_CheckRef(type_instance_.obj()));
-  PyObject* inst = PyWeakref_GET_OBJECT(type_instance_.obj());
-  if (inst != Py_None) {
-    // Cached instance still alive
-    Py_INCREF(inst);
+  PyObject* inst = NULL;
+  int result = PyWeakref_GetRef(type_instance_.obj(), &inst);
+  if (result == 1) {
+    // Alive: inst is a new strong reference
     return inst;
-  } else {
-    // Must reconstruct from serialized form
+  } else if (result == 0) {
+    // Weakref is dead, must reconstruct from serialized form
     // XXX cache again?
     return DeserializeExtInstance(type_class_.obj(), storage_type_, 
serialized_);
+  } else {
+    // -1 = exception
+    return nullptr;
   }
 }