PyAPI: add function to get an RNA subclass

This is inconvenient in regular Python, add a class-method
to perform the operation, eg:

bpy.types.Node.bl_rna_find_subclass("CustomNodeType")

1 files changed, 61 insertions, 0 deletions

diff --git a/source/blender/python/intern/bpy_rna.c b/source/blender/python/intern/bpy_rna.c
index dfd643319e5..6a1016584af 100644
--- a/source/blender/python/intern/bpy_rna.c
+++ b/source/blender/python/intern/bpy_rna.c
@@ -3707,6 +3707,66 @@ static PyObject *pyrna_struct_type_recast(BPy_StructRNA *self)
 	return pyrna_struct_CreatePyObject(&r_ptr);
 }
 
+/**
+ * \note Return value is borrowed, caller must incref.
+ */
+static PyObject *pyrna_struct_bl_rna_find_subclass_recursive(PyObject *cls, const char *id)
+{
+	PyObject *ret_test = NULL;
+	PyObject *subclasses = ((PyTypeObject *)cls)->tp_subclasses;
+	if (subclasses) {
+		/* Unfortunately we can't use the dict key because Python class names
+		 * don't match the bl_idname used internally. */
+		BLI_assert(PyDict_CheckExact(subclasses));
+		PyObject *key = NULL;
+		Py_ssize_t pos = 0;
+		PyObject *value = NULL;
+		while (PyDict_Next(subclasses, &pos, &key, &value)) {
+			BLI_assert(PyWeakref_CheckRef(value));
+			PyObject *subcls = PyWeakref_GET_OBJECT(value);
+			if (subcls != Py_None) {
+				BPy_StructRNA *py_srna = (BPy_StructRNA *)PyDict_GetItem(
+				        ((PyTypeObject *)subcls)->tp_dict, bpy_intern_str_bl_rna);
+				if (py_srna) {
+					StructRNA *srna = py_srna->ptr.data;
+					if (STREQ(id, RNA_struct_identifier(srna))) {
+						ret_test = subcls;
+						break;
+					}
+				}
+				ret_test = pyrna_struct_bl_rna_find_subclass_recursive(subcls, id);
+				if (ret_test) {
+					break;
+				}
+			}
+		}
+	}
+	return ret_test;
+}
+
+PyDoc_STRVAR(pyrna_struct_bl_rna_get_subclass_doc,
+".. classmethod:: bl_rna_get_subclass(id, default=None)\n"
+"\n"
+"   :arg id: The RNA type identifier.\n"
+"   :type vector: string\n"
+"   :return: The class or default when not found.\n"
+"   :rtype: type\n"
+);
+static PyObject *pyrna_struct_bl_rna_get_subclass(PyObject *cls, PyObject *args)
+{
+	char *id;
+	PyObject *ret_default = Py_None;
+
+	if (!PyArg_ParseTuple(args, "s|O:bl_rna_find_subclass", &id, &ret_default)) {
+		return NULL;
+	}
+	PyObject *ret = pyrna_struct_bl_rna_find_subclass_recursive(cls, id);
+	if (ret == NULL) {
+		ret = ret_default;
+	}
+	return Py_INCREF_RET(ret);
+}
+
 static void pyrna_dir_members_py__add_keys(PyObject *list, PyObject *dict)
 {
 	PyObject *list_tmp;
@@ -5005,6 +5065,7 @@ static struct PyMethodDef pyrna_struct_methods[] = {
 	{"path_resolve", (PyCFunction)pyrna_struct_path_resolve, METH_VARARGS, pyrna_struct_path_resolve_doc},
 	{"path_from_id", (PyCFunction)pyrna_struct_path_from_id, METH_VARARGS, pyrna_struct_path_from_id_doc},
 	{"type_recast", (PyCFunction)pyrna_struct_type_recast, METH_NOARGS, pyrna_struct_type_recast_doc},
+	{"bl_rna_get_subclass", (PyCFunction) pyrna_struct_bl_rna_get_subclass, METH_VARARGS | METH_CLASS, pyrna_struct_bl_rna_get_subclass_doc},
 	{"__dir__", (PyCFunction)pyrna_struct_dir, METH_NOARGS, NULL},
 
 	/* experimental */