Make Scene Master collection 'Private' ID data, like root nodetrees.

Same issue here as with root nodetrees, those are private ID data owned
by another ID, and not in Main DB. This requires special handling.

there are still quiet a few things to do here, like getting rid of
special code for master collection (regular ID copying should handle
that just as it already does for root nodetrees), cleanup in ID copying
code, etc.

4 files changed, 24 insertions, 4 deletions

diff --git a/source/blender/blenkernel/BKE_blender_version.h b/source/blender/blenkernel/BKE_blender_version.h
index e0f89024420..db93193bfe3 100644
--- a/source/blender/blenkernel/BKE_blender_version.h
+++ b/source/blender/blenkernel/BKE_blender_version.h
@@ -27,7 +27,7 @@
  * \note Use #STRINGIFY() rather than defining with quotes.
  */
 #define BLENDER_VERSION 281
-#define BLENDER_SUBVERSION 4
+#define BLENDER_SUBVERSION 5
 /** Several breakages with 280, e.g. collections vs layers. */
 #define BLENDER_MINVERSION 280
 #define BLENDER_MINSUBVERSION 0
diff --git a/source/blender/blenkernel/intern/collection.c b/source/blender/blenkernel/intern/collection.c
index 2031576190e..06710b40569 100644
--- a/source/blender/blenkernel/intern/collection.c
+++ b/source/blender/blenkernel/intern/collection.c
@@ -338,8 +338,9 @@ Collection *BKE_collection_duplicate(Main *bmain,
                                      const bool do_obdata)
 {
   /* It's not allowed to copy the master collection. */
+  BLI_assert((collection->id.flag & LIB_PRIVATE_DATA) == 0);
+  BLI_assert((collection->flag & COLLECTION_IS_MASTER) == 0);
   if (collection->flag & COLLECTION_IS_MASTER) {
-    BLI_assert("!Master collection can't be duplicated");
     return NULL;
   }
 
@@ -368,6 +369,7 @@ Collection *BKE_collection_duplicate(Main *bmain,
 Collection *BKE_collection_copy_master(Main *bmain, Collection *collection, const int flag)
 {
   BLI_assert(collection->flag & COLLECTION_IS_MASTER);
+  BLI_assert(collection->id.flag & LIB_PRIVATE_DATA);
 
   Collection *collection_dst = MEM_dupallocN(collection);
   BKE_collection_copy_data(bmain, collection_dst, collection, flag);
@@ -499,6 +501,7 @@ Collection *BKE_collection_master_add()
   /* Not an actual datablock, but owned by scene. */
   Collection *master_collection = MEM_callocN(sizeof(Collection), "Master Collection");
   STRNCPY(master_collection->id.name, "GRMaster Collection");
+  master_collection->id.flag |= LIB_PRIVATE_DATA;
   master_collection->flag |= COLLECTION_IS_MASTER;
   return master_collection;
 }
diff --git a/source/blender/blenloader/intern/versioning_280.c b/source/blender/blenloader/intern/versioning_280.c
index ed3b1613b2a..00c0ed561f7 100644
--- a/source/blender/blenloader/intern/versioning_280.c
+++ b/source/blender/blenloader/intern/versioning_280.c
@@ -3704,12 +3704,23 @@ void blo_do_versions_280(FileData *fd, Library *UNUSED(lib), Main *bmain)
     FOREACH_MAIN_ID_END;
   }
 
-  {
-    /* Versioning code until next subversion bump goes here. */
+  if (!MAIN_VERSION_ATLEAST(bmain, 281, 5)) {
     for (Brush *br = bmain->brushes.first; br; br = br->id.next) {
       if (br->ob_mode & OB_MODE_SCULPT && br->normal_radius_factor == 0.0f) {
         br->normal_radius_factor = 0.5f;
       }
     }
+
+    LISTBASE_FOREACH (Scene *, scene, &bmain->scenes) {
+      /* Older files do not hqve a msater collection, which is then added through
+       * `BKE_collection_master_add()`, so everything is fine. */
+      if (scene->master_collection != NULL) {
+        scene->master_collection->id.flag |= LIB_PRIVATE_DATA;
+      }
+    }
+  }
+
+  {
+    /* Versioning code until next subversion bump goes here. */
   }
 }
diff --git a/source/blender/makesrna/intern/rna_access.c b/source/blender/makesrna/intern/rna_access.c
index bc015a378cc..531c2ef2003 100644
--- a/source/blender/makesrna/intern/rna_access.c
+++ b/source/blender/makesrna/intern/rna_access.c
@@ -41,6 +41,7 @@
 #include "BLT_translation.h"
 
 #include "BKE_animsys.h"
+#include "BKE_collection.h"
 #include "BKE_context.h"
 #include "BKE_idcode.h"
 #include "BKE_idprop.h"
@@ -5778,6 +5779,11 @@ ID *RNA_find_real_ID_and_path(Main *bmain, ID *id, const char **r_path)
           *r_path = "node_tree";
         }
         return BKE_node_tree_find_owner_ID(bmain, (bNodeTree *)id);
+      case ID_GR:
+        if (r_path) {
+          *r_path = "collection";
+        }
+        return (ID *)BKE_collection_master_scene_search(bmain, (Collection *)id);
 
       default:
         return NULL;