From 37b4384b59c09684ac4ece5e39bf20187968f737 Mon Sep 17 00:00:00 2001
From: Bastien Montagne <montagne29@wanadoo.fr>
Date: Mon, 12 Aug 2019 15:37:58 +0200
Subject: Fix T67032: Do not systematically link 'orphaned' indirectly linked
 objects to scene.

Not even in append case. If those objects are already part of a
collection, we can now leave them fully un-instantiated in any scene,
since user can easily do it themselves as they need to.
---
 source/blender/blenloader/intern/readfile.c | 42 +++++++++++++++++------------
 1 file changed, 25 insertions(+), 17 deletions(-)

diff --git a/source/blender/blenloader/intern/readfile.c b/source/blender/blenloader/intern/readfile.c
index 9a4fde8cc42..65120fc4c10 100644
--- a/source/blender/blenloader/intern/readfile.c
+++ b/source/blender/blenloader/intern/readfile.c
@@ -11129,6 +11129,19 @@ static bool object_in_any_scene(Main *bmain, Object *ob)
   return false;
 }
 
+static bool object_in_any_collection(Main *bmain, Object *ob)
+{
+  Collection *collection;
+
+  for (collection = bmain->collections.first; collection; collection = collection->id.next) {
+    if (BKE_collection_has_object(collection, ob)) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
 static void add_loose_objects_to_scene(Main *mainvar,
                                        Main *bmain,
                                        Scene *scene,
@@ -11138,7 +11151,7 @@ static void add_loose_objects_to_scene(Main *mainvar,
                                        const short flag)
 {
   Collection *active_collection = NULL;
-  const bool is_link = (flag & FILE_LINK) != 0;
+  const bool do_append = (flag & FILE_LINK) == 0;
 
   BLI_assert(scene);
 
@@ -11147,14 +11160,13 @@ static void add_loose_objects_to_scene(Main *mainvar,
   for (Object *ob = mainvar->objects.first; ob; ob = ob->id.next) {
     bool do_it = (ob->id.tag & LIB_TAG_DOIT) != 0;
     if (do_it || ((ob->id.tag & LIB_TAG_INDIRECT) && (ob->id.tag & LIB_TAG_PRE_EXISTING) == 0)) {
-      if (!is_link) {
+      if (do_append) {
         if (ob->id.us == 0) {
           do_it = true;
         }
-        else if ((ob->id.lib == lib) && (object_in_any_scene(bmain, ob) == 0)) {
-          /* When appending, make sure any indirectly loaded objects get a base,
-           * else they cant be accessed at all
-           * (see T27437). */
+        else if ((ob->id.lib == lib) && (object_in_any_collection(bmain, ob) == 0)) {
+          /* When appending, make sure any indirectly loaded object gets a base,
+           * when they are not part of any collection yet. */
           do_it = true;
         }
       }
@@ -11204,8 +11216,6 @@ static void add_collections_to_scene(Main *mainvar,
                                      Library *lib,
                                      const short flag)
 {
-  const bool do_append = (flag & FILE_LINK) == 0;
-
   Collection *active_collection = scene->master_collection;
   if (flag & FILE_ACTIVE_COLLECTION) {
     LayerCollection *lc = BKE_layer_collection_get_active(view_layer);
@@ -11244,12 +11254,10 @@ static void add_collections_to_scene(Main *mainvar,
       ob->transflag |= OB_DUPLICOLLECTION;
       copy_v3_v3(ob->loc, scene->cursor.location);
     }
-    /* We do not want to force instantiation of indirectly linked collections...
-     * Except when we are appending (since in that case, we'll end up instantiating all objects,
-     * it's better to do it via their own collections if possible).
-     * Reports showing that desired difference in behaviors between link and append:
-     * See T62570, T61796. */
-    else if (do_append || (collection->id.tag & LIB_TAG_INDIRECT) == 0) {
+    /* We do not want to force instantiation of indirectly linked collections,
+     * not even when appending. Users can now easily instantiate collections (and their objects)
+     * as needed by themsleves. See T67032. */
+    else if ((collection->id.tag & LIB_TAG_INDIRECT) == 0) {
       bool do_add_collection = (collection->id.tag & LIB_TAG_DOIT) != 0;
       if (!do_add_collection) {
         /* We need to check that objects in that collections are already instantiated in a scene.
@@ -11261,9 +11269,8 @@ static void add_collections_to_scene(Main *mainvar,
         for (CollectionObject *coll_ob = collection->gobject.first; coll_ob != NULL;
              coll_ob = coll_ob->next) {
           Object *ob = coll_ob->ob;
-          if ((ob->id.tag & LIB_TAG_PRE_EXISTING) == 0 && (ob->id.tag & LIB_TAG_DOIT) == 0 &&
-              (do_append || (ob->id.tag & LIB_TAG_INDIRECT) == 0) && (ob->id.lib == lib) &&
-              (object_in_any_scene(bmain, ob) == 0)) {
+          if ((ob->id.tag & (LIB_TAG_PRE_EXISTING | LIB_TAG_DOIT | LIB_TAG_INDIRECT)) == 0 &&
+              (ob->id.lib == lib) && (object_in_any_scene(bmain, ob) == 0)) {
             do_add_collection = true;
             break;
           }
@@ -11285,6 +11292,7 @@ static void add_collections_to_scene(Main *mainvar,
           }
         }
 
+        /* Those are kept for safety and consistency, but should not be needed anymore? */
         collection->id.tag &= ~LIB_TAG_INDIRECT;
         collection->id.tag |= LIB_TAG_EXTERN;
       }
-- 
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