Asset System: Data-block asset metadata storage, reading and API

Asset metadata is what turns a regular data-block into an asset. It is a small
data-structure, but a key part of the technical design of the asset system.

The design foresees that asset data-blocks store an `ID.asset_data` pointer of
type `AssetMetaData`. This data **must not** have dependencies on other
data-blocks or data-block data, it must be an independent unit. That way we can
read asset-metadata from .blends without reading anything else from the file.
The Asset Browser will use this metadata (together with the data-block name,
preview and file path) to represent assets in the file list.

Includes:
* New `ID.asset_data` for asset metadata.
* Asset tags, description and custom properties.
* BKE code to manage asset meta-data and asset tags.
* Code to read asset data from files, without reading IDs.
* RNA for asset metadata (including tags)

Part of the first Asset Browser milestone. Check the #asset_browser_milestone_1
project milestone on developer.blender.org.

Differential Revision: https://developer.blender.org/D9716

Reviewed by: Bastien Montagne, Brecht Van Lommel

1 files changed, 5 insertions, 0 deletions

diff --git a/source/blender/blenkernel/intern/lib_id_delete.c b/source/blender/blenkernel/intern/lib_id_delete.c
index 1e45a3c1163..7199bd0f13c 100644
--- a/source/blender/blenkernel/intern/lib_id_delete.c
+++ b/source/blender/blenkernel/intern/lib_id_delete.c
@@ -31,6 +31,7 @@
 #include "BLI_listbase.h"
 
 #include "BKE_anim_data.h"
+#include "BKE_asset.h"
 #include "BKE_idprop.h"
 #include "BKE_idtype.h"
 #include "BKE_key.h"
@@ -64,6 +65,10 @@ void BKE_libblock_free_data(ID *id, const bool do_id_user)
     id->override_library = NULL;
   }
 
+  if (id->asset_data) {
+    BKE_asset_metadata_free(&id->asset_data);
+  }
+
   BKE_animdata_free(id, do_id_user);
 }