Add sq_ass_item slot macro

Author: jim-easterbrook

src/interface/shared/slots.i

@@ -46,6 +46,50 @@ static PyObject* __getitem__%mangle(type)_closure(
 %enddef // SQ_ITEM
 
 
+// Macro to add sq_ass_item slot and functions
+%define SQ_ASS_ITEM(type, item_type, setfunc, delfunc)
+// Use %inline so SWIG generates wrappers with type conversions.
+// Names start with '_' so it's invisible in normal use.
+%noexception __setitem__%mangle(Exiv2::ValueType<item_type>);
+%noexception __delitem__%mangle(Exiv2::ValueType<item_type>);
+%inline %{
+static void __setitem__%mangle(Exiv2::ValueType<item_type>)(
+        Exiv2::ValueType<item_type>* self, size_t idx, item_type value) {
+    setfunc;
+};
+static void __delitem__%mangle(Exiv2::ValueType<item_type>)(
+        Exiv2::ValueType<item_type>* self, size_t idx) {
+    delfunc;
+};
+%}
+%fragment("__setitem__"{type}, "header") {
+extern "C" {
+static PyObject* _wrap___setitem__%mangle(type)(PyObject*, PyObject*);
+static PyObject* _wrap___delitem__%mangle(type)(PyObject*, PyObject*);
+}
+static int __setitem__%mangle(type)_closure(
+        PyObject* self, Py_ssize_t idx, PyObject* value) {
+    PyObject* args;
+    PyObject* result;
+    if (value) {
+        args = Py_BuildValue("(OnO)", self, idx, value);
+        result = _wrap___setitem__%mangle(type)(self, args);
+    } else {
+        args = Py_BuildValue("(On)", self, idx);
+        result = _wrap___delitem__%mangle(type)(self, args);
+    }
+    Py_DECREF(args);
+    if (!result)
+        return -1;
+    Py_DECREF(result);
+    return 0;
+};
+}
+%fragment("__setitem__"{type});
+%feature("python:sq_ass_item") type QUOTE(__setitem__%mangle(type)_closure);
+%enddef // SQ_ASS_ITEM
+
+
 // Macro to add sq_length slot and function
 %define SQ_LENGTH(type, func)
 %fragment("__len__"{type}, "header") {

src/interface/value.i

@@ -236,7 +236,6 @@ DEPRECATED_ENUM(XmpValue, XmpStruct)
 %ignore type_name::copy(byte *) const;
 %ignore type_name::read(byte const *, BUFLEN_T);
 %noexception type_name::~part_name;
-%noexception type_name::__setitem__;
 %noexception type_name::append;
 %noexception type_name::count;
 %noexception type_name::size;
@@ -276,15 +275,9 @@ VALUE_SUBCLASS(Exiv2::ValueType<item_type>, type_name)
     std::pair< unsigned int,unsigned int > const &);
 // Access values as a list
 SQ_ITEM(Exiv2::ValueType<item_type>, item_type, self->value_[idx])
-#if SWIG_VERSION >= 0x040201
-%feature("python:slot", "sq_ass_item", functype="ssizeobjargproc")
-    Exiv2::ValueType<item_type>::__setitem__;
-#else
-// sq_ass_item segfaults when used to delete element
-// See https://github.com/swig/swig/pull/2771
-%feature("python:slot", "mp_ass_subscript", functype="objobjargproc")
-    Exiv2::ValueType<item_type>::__setitem__;
-#endif // SWIG_VERSION
+SQ_ASS_ITEM(Exiv2::ValueType<item_type>, item_type,
+            self->value_[idx] = value,
+            self->value_.erase(self->value_.begin() + idx))
 %feature("docstring") Exiv2::ValueType<item_type>
 "Sequence of " #item_type " values.\n"
 "The data components can be accessed like a Python list."
@@ -299,12 +292,6 @@ SQ_ITEM(Exiv2::ValueType<item_type>, item_type, self->value_[idx])
         result->value_ = value;
         return result;
     }
-    void __setitem__(size_t idx, const item_type* INPUT) {
-        if (INPUT)
-            $self->value_[idx] = *INPUT;
-        else
-            $self->value_.erase($self->value_.begin() + idx);
-    }
     void append(item_type value) {
         $self->value_.push_back(value);
     }