Bmesh: Deprecate deform parameter of from_object()

The deform parameter of the Bmesh from_object method is deprecated,
always assumed to be True, and will be removed in version 3.0.

That is because the cases where it is False don't work correctly and are
subject to memory leaks. One of the symptoms of the incorrect behavior
is the application of constructive modifiers twice if the input object
is an evaluated one, as demonstrated in D10053.

Reviewed By: Brecht

Differential Revision: https://developer.blender.org/D10086

1 files changed, 24 insertions, 28 deletions

diff --git a/source/blender/python/bmesh/bmesh_py_types.c b/source/blender/python/bmesh/bmesh_py_types.c
index 38122c45ef1..22c7a394906 100644
--- a/source/blender/python/bmesh/bmesh_py_types.c
+++ b/source/blender/python/bmesh/bmesh_py_types.c
@@ -1079,7 +1079,12 @@ PyDoc_STRVAR(
     "   :arg cage: Get the mesh as a deformed cage.\n"
     "   :type cage: boolean\n"
     "   :arg face_normals: Calculate face normals.\n"
-    "   :type face_normals: boolean\n");
+    "   :type face_normals: boolean\n"
+    "\n"
+    "   .. deprecated:: 2.93\n"
+    "\n"
+    "      The deform parameter is deprecated, assumed to be True, and will be removed in version "
+    "3.0.\n");
 static PyObject *bpy_bmesh_from_object(BPy_BMesh *self, PyObject *args, PyObject *kw)
 {
   static const char *kwlist[] = {"object", "depsgraph", "deform", "cage", "face_normals", NULL};
@@ -1120,45 +1125,36 @@ static PyObject *bpy_bmesh_from_object(BPy_BMesh *self, PyObject *args, PyObject
     return NULL;
   }
 
+  if (use_deform == false) {
+    PyErr_WarnEx(PyExc_FutureWarning,
+                 "from_object(...): the deform parameter is deprecated, assumed to be True, and "
+                 "will be removed in version 3.0",
+                 1);
+  }
+
   const bool use_render = DEG_get_mode(depsgraph) == DAG_EVAL_RENDER;
   scene_eval = DEG_get_evaluated_scene(depsgraph);
   ob_eval = DEG_get_evaluated_object(depsgraph, ob);
   bool need_free = false;
 
   /* Write the display mesh into the dummy mesh */
-  if (use_deform) {
-    if (use_render) {
-      if (use_cage) {
-        PyErr_SetString(PyExc_ValueError,
-                        "from_object(...): cage arg is unsupported when dependency graph "
-                        "evaluation mode is RENDER");
-        return NULL;
-      }
-
-      me_eval = BKE_mesh_new_from_object(depsgraph, ob_eval, true);
-      need_free = true;
-    }
-    else {
-      if (use_cage) {
-        me_eval = mesh_get_eval_deform(depsgraph, scene_eval, ob_eval, &data_masks);
-      }
-      else {
-        me_eval = mesh_get_eval_final(depsgraph, scene_eval, ob_eval, &data_masks);
-      }
-    }
-  }
-  else {
-    /* !use_deform */
+  if (use_render) {
     if (use_cage) {
       PyErr_SetString(PyExc_ValueError,
-                      "from_object(...): cage arg is unsupported when deform=False");
+                      "from_object(...): cage arg is unsupported when dependency graph "
+                      "evaluation mode is RENDER");
       return NULL;
     }
-    if (use_render) {
-      me_eval = mesh_create_eval_no_deform_render(depsgraph, scene_eval, ob, &data_masks);
+
+    me_eval = BKE_mesh_new_from_object(depsgraph, ob_eval, true);
+    need_free = true;
+  }
+  else {
+    if (use_cage) {
+      me_eval = mesh_get_eval_deform(depsgraph, scene_eval, ob_eval, &data_masks);
     }
     else {
-      me_eval = mesh_create_eval_no_deform(depsgraph, scene_eval, ob, &data_masks);
+      me_eval = mesh_get_eval_final(depsgraph, scene_eval, ob_eval, &data_masks);
     }
   }