From dab04bc0536feb37140d7644ba5bc6ba8588699c Mon Sep 17 00:00:00 2001
From: Jacques Lucke <jacques@blender.org>
Date: Tue, 23 Nov 2021 14:35:49 +0100
Subject: Fix T93231: crash when overwriting vertex group with other domain

The problem was that we forgot to actually remove the vertex group when
it should be deleted. We only removed all the data that was attached to it.

Differential Revision: https://developer.blender.org/D13326
---
 source/blender/blenkernel/BKE_deform.h             |  4 ++++
 source/blender/blenkernel/intern/deform.c          | 28 ++++++++++++++++++++--
 .../blenkernel/intern/geometry_component_mesh.cc   | 11 +++++----
 3 files changed, 37 insertions(+), 6 deletions(-)

diff --git a/source/blender/blenkernel/BKE_deform.h b/source/blender/blenkernel/BKE_deform.h
index f4221d57428..cca99f9d1cd 100644
--- a/source/blender/blenkernel/BKE_deform.h
+++ b/source/blender/blenkernel/BKE_deform.h
@@ -50,6 +50,10 @@ void BKE_object_defgroup_active_index_set(struct Object *ob, const int new_index
 const struct ListBase *BKE_id_defgroup_list_get(const struct ID *id);
 struct ListBase *BKE_id_defgroup_list_get_mutable(struct ID *id);
 int BKE_id_defgroup_name_index(const struct ID *id, const char *name);
+bool BKE_id_defgroup_name_find(const struct ID *id,
+                               const char *name,
+                               int *r_index,
+                               struct bDeformGroup **r_group);
 
 struct bDeformGroup *BKE_object_defgroup_new(struct Object *ob, const char *name);
 void BKE_defgroup_copy_list(struct ListBase *outbase, const struct ListBase *inbase);
diff --git a/source/blender/blenkernel/intern/deform.c b/source/blender/blenkernel/intern/deform.c
index 13222747a52..a2f285dab51 100644
--- a/source/blender/blenkernel/intern/deform.c
+++ b/source/blender/blenkernel/intern/deform.c
@@ -557,11 +557,35 @@ bDeformGroup *BKE_object_defgroup_find_name(const Object *ob, const char *name)
 
 int BKE_id_defgroup_name_index(const ID *id, const char *name)
 {
-  if (name == NULL || name[0] == '\0') {
+  int index;
+  if (!BKE_id_defgroup_name_find(id, name, &index, NULL)) {
     return -1;
   }
+  return index;
+}
+
+bool BKE_id_defgroup_name_find(const struct ID *id,
+                               const char *name,
+                               int *r_index,
+                               struct bDeformGroup **r_group)
+{
+  if (name == NULL || name[0] == '\0') {
+    return false;
+  }
   const ListBase *defbase = BKE_id_defgroup_list_get(id);
-  return BLI_findstringindex(defbase, name, offsetof(bDeformGroup, name));
+  int index;
+  LISTBASE_FOREACH_INDEX (bDeformGroup *, group, defbase, index) {
+    if (STREQ(name, group->name)) {
+      if (r_index != NULL) {
+        *r_index = index;
+      }
+      if (r_group != NULL) {
+        *r_group = group;
+      }
+      return true;
+    }
+  }
+  return false;
 }
 
 const ListBase *BKE_object_defgroup_list(const Object *ob)
diff --git a/source/blender/blenkernel/intern/geometry_component_mesh.cc b/source/blender/blenkernel/intern/geometry_component_mesh.cc
index c3e39c0b2cb..0456316151c 100644
--- a/source/blender/blenkernel/intern/geometry_component_mesh.cc
+++ b/source/blender/blenkernel/intern/geometry_component_mesh.cc
@@ -1134,16 +1134,19 @@ class VertexGroupsAttributeProvider final : public DynamicAttributesProvider {
     }
 
     const std::string name = attribute_id.name();
-    const int vertex_group_index = BLI_findstringindex(
-        &mesh->vertex_group_names, name.c_str(), offsetof(bDeformGroup, name));
-    if (vertex_group_index < 0) {
+
+    int index;
+    bDeformGroup *group;
+    if (!BKE_id_defgroup_name_find(&mesh->id, name.c_str(), &index, &group)) {
       return false;
     }
+    BLI_remlink(&mesh->vertex_group_names, group);
+    MEM_freeN(group);
     if (mesh->dvert == nullptr) {
       return true;
     }
     for (MDeformVert &dvert : MutableSpan(mesh->dvert, mesh->totvert)) {
-      MDeformWeight *weight = BKE_defvert_find_index(&dvert, vertex_group_index);
+      MDeformWeight *weight = BKE_defvert_find_index(&dvert, index);
       BKE_defvert_remove_group(&dvert, weight);
     }
     return true;
-- 
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