From b6ad0735a6b0a84aaee20d072bf218e262e8bb89 Mon Sep 17 00:00:00 2001
From: Bastien Montagne <bastien@blender.org>
Date: Tue, 5 Oct 2021 10:45:28 +0200
Subject: Fix T86379: When using "Append" not handling properly RigidBody
 constraints

This was simply never handled apparently.

Also fixes a regression from recent append refactor that prevented RB
objects to to properly handled too (since we instantiate loose objects
in append step now, we need to handle RigidBody ones after that
instantiation stage, otherwise nothing will happen since loose objects
won't be in any scene).
---
 source/blender/blenkernel/intern/rigidbody.c       | 49 ++++++++++++++++++----
 .../blender/windowmanager/intern/wm_files_link.c   | 13 ++++--
 2 files changed, 52 insertions(+), 10 deletions(-)

diff --git a/source/blender/blenkernel/intern/rigidbody.c b/source/blender/blenkernel/intern/rigidbody.c
index 1ea659b2d41..242bad163d8 100644
--- a/source/blender/blenkernel/intern/rigidbody.c
+++ b/source/blender/blenkernel/intern/rigidbody.c
@@ -1473,16 +1473,51 @@ static bool rigidbody_add_object_to_scene(Main *bmain, Scene *scene, Object *ob)
   return true;
 }
 
-void BKE_rigidbody_ensure_local_object(Main *bmain, Object *ob)
+static bool rigidbody_add_constraint_to_scene(Main *bmain, Scene *scene, Object *ob)
 {
-  if (ob->rigidbody_object == NULL) {
-    return;
+  /* Add rigid body world and group if they don't exist for convenience */
+  RigidBodyWorld *rbw = BKE_rigidbody_get_world(scene);
+  if (rbw == NULL) {
+    rbw = BKE_rigidbody_create_world(scene);
+    if (rbw == NULL) {
+      return false;
+    }
+
+    BKE_rigidbody_validate_sim_world(scene, rbw, false);
+    scene->rigidbody_world = rbw;
   }
 
-  /* Add newly local object to scene. */
-  for (Scene *scene = bmain->scenes.first; scene; scene = scene->id.next) {
-    if (BKE_scene_object_find(scene, ob)) {
-      rigidbody_add_object_to_scene(bmain, scene, ob);
+  if (rbw->constraints == NULL) {
+    rbw->constraints = BKE_collection_add(bmain, NULL, "RigidBodyConstraints");
+    id_fake_user_set(&rbw->constraints->id);
+  }
+
+  /* Add object to rigid body group. */
+  BKE_collection_object_add(bmain, rbw->constraints, ob);
+  BKE_rigidbody_cache_reset(rbw);
+
+  DEG_relations_tag_update(bmain);
+  DEG_id_tag_update(&rbw->constraints->id, ID_RECALC_COPY_ON_WRITE);
+
+  return true;
+}
+
+void BKE_rigidbody_ensure_local_object(Main *bmain, Object *ob)
+{
+  if (ob->rigidbody_object != NULL) {
+    /* Add newly local object to scene. */
+    for (Scene *scene = bmain->scenes.first; scene; scene = scene->id.next) {
+      if (BKE_scene_object_find(scene, ob)) {
+        rigidbody_add_object_to_scene(bmain, scene, ob);
+      }
+    }
+  }
+  if (ob->rigidbody_constraint != NULL) {
+    /* Add newly local object to scene. */
+    for (Scene *scene = bmain->scenes.first; scene; scene = scene->id.next) {
+      if (BKE_scene_object_find(scene, ob)) {
+        rigidbody_add_constraint_to_scene(bmain, scene, ob);
+      }
     }
   }
 }
diff --git a/source/blender/windowmanager/intern/wm_files_link.c b/source/blender/windowmanager/intern/wm_files_link.c
index a73bea31669..cf3536213d2 100644
--- a/source/blender/windowmanager/intern/wm_files_link.c
+++ b/source/blender/windowmanager/intern/wm_files_link.c
@@ -579,6 +579,16 @@ static void wm_append_loose_data_instantiate(WMLinkAppendData *lapp_data,
 
     id->tag &= ~LIB_TAG_DOIT;
   }
+
+  /* Finally, add rigid body objects and constraints to current RB world(s). */
+  for (itemlink = lapp_data->items.list; itemlink; itemlink = itemlink->next) {
+    WMLinkAppendDataItem *item = itemlink->link;
+    ID *id = wm_append_loose_data_instantiate_process_check(item);
+    if (id == NULL || GS(id->name) != ID_OB) {
+      continue;
+    }
+    BKE_rigidbody_ensure_local_object(bmain, (Object *)id);
+  }
 }
 
 /** \} */
@@ -773,9 +783,6 @@ static void wm_append_do(WMLinkAppendData *lapp_data,
                                                  local_appended_new_id);
       }
 
-      if (GS(local_appended_new_id->name) == ID_OB) {
-        BKE_rigidbody_ensure_local_object(bmain, (Object *)local_appended_new_id);
-      }
       if (set_fakeuser) {
         if (!ELEM(GS(local_appended_new_id->name), ID_OB, ID_GR)) {
           /* Do not set fake user on objects nor collections (instancing). */
-- 
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