Add python builtin testcase for handling NULL in a couple of closures

From and for testing issue #2771.

CHANGES.current

@@ -7,6 +7,10 @@ the issue number to the end of the URL: https://github.com/swig/swig/issues/
 Version 4.2.1 (in progress)
 ===========================
 
+2024-01-31: jim-easterbrook
+            #2771 [Python] builtin fixes to handle NULL values passed to slots using
+            functype: ssizeobjargproc and ternaryfunc.
+
 2024-01-31: olly
 	    [java] #2766 Fix segfault trying to wrap a constant whose type is unknown
 	    to SWIG with "%javaconst(1);" enabled.

Examples/test-suite/python/python_builtin_runme.py

@@ -111,3 +111,26 @@ z = ANumber(9)
 z = pow(x, y, z)
 if z.Value() != 7:
   raise RuntimeError("pow(x, y, z) wrong")
+
+# Test 8 https://github.com/swig/swig/pull/2771 __setitem__ for deleting item, uses C NULL
+def check_gsi(gsi, idx, value, args_count, kw_count):
+  if gsi.idx != idx:
+    raise RuntimeError("idx wrong {}".format(idx))
+  if gsi.value != value:
+    raise RuntimeError("value wrong {}".format(value))
+  if gsi.args_count != args_count:
+    raise RuntimeError("args_count wrong {}".format(args_count))
+  if gsi.kw_count != kw_count:
+    raise RuntimeError("kw_count wrong {}".format(kw_count))
+  gsi.reset()
+
+if is_python_builtin():
+  gsi = GetSetItem()
+  gsi[0] = 111
+  check_gsi(gsi, 0, 111, -100, -100)
+  del gsi[0]
+  check_gsi(gsi, 0, -11, -100, -100)
+  gsi(222, fred = 333, jack = 444)
+  check_gsi(gsi, -100, -100, 1, 2)
+  gsi(333)
+  check_gsi(gsi, -100, -100, 1, -11)

Examples/test-suite/python_builtin.i

@@ -244,3 +244,35 @@ public:
   }
 };
 %}
+
+// Test 8 https://github.com/swig/swig/pull/2771 __setitem__ for deleting item, uses C NULL
+%feature("python:slot", "sq_item", functype="ssizeargfunc") GetSetItem::__getitem__;
+%feature("python:slot", "sq_ass_item", functype="ssizeobjargproc") GetSetItem::__setitem__;
+%feature("python:slot", "tp_call", functype="ternaryfunc") GetSetItem::__call__;
+%typemap(default) PyObject* value {$1 = NULL;}
+
+%inline %{
+class GetSetItem {
+public:
+  int idx, value, args_count, kw_count;
+  GetSetItem() : idx(), value(), args_count(), kw_count() { reset(); }
+  int __getitem__(int idx) {
+    this->idx = idx;
+    return 123;
+  }
+  void __setitem__(int idx, PyObject* value) {
+    this->idx = idx;
+    this->value = value ? (int)PyInt_AsLong(value) : -11;
+  }
+  void __call__(PyObject* args, PyObject* kw) {
+    this->args_count = args ? (int)PyTuple_Size(args) : -11;
+    this->kw_count = kw ? (int)PyDict_Size(kw) : -11;
+  }
+  void reset() {
+    idx = -100;
+    value = -100;
+    args_count = -100;
+    kw_count = -100;
+  }
+};
+%}