PyAPI: add bpy.types.BlendFile.temp_data for temporary library loading

This adds support for creating a `BlendFile` (internally called `Main`),
which is limited to a context.

Temporary data can now be created which can then use
`.libraries.load()` the same as with `bpy.data`.

To prevent errors caused by mixing the temporary ID's with data in
`bpy.data` they are tagged as temporary so they can't be assigned
to properties, however they can be passed as arguments to functions.

Reviewed By: mont29, sybren

Ref D10612

1 files changed, 3 insertions, 1 deletions

diff --git a/source/blender/blenloader/intern/versioning_250.c b/source/blender/blenloader/intern/versioning_250.c
index 983fdce15f1..467fd8b0399 100644
--- a/source/blender/blenloader/intern/versioning_250.c
+++ b/source/blender/blenloader/intern/versioning_250.c
@@ -449,7 +449,9 @@ static void versions_gpencil_add_main(ListBase *lb, ID *id, const char *name)
   BKE_id_new_name_validate(lb, id, name);
   /* alphabetic insertion: is in BKE_id_new_name_validate */
 
-  BKE_lib_libblock_session_uuid_ensure(id);
+  if ((id->tag & LIB_TAG_TEMP_MAIN) == 0) {
+    BKE_lib_libblock_session_uuid_ensure(id);
+  }
 
   if (G.debug & G_DEBUG) {
     printf("Converted GPencil to ID: %s\n", id->name + 2);