glTF exporter: manage user extension at gltf level

io_scene_gltf2/__init__.py

@@ -15,7 +15,7 @@
 bl_info = {
     'name': 'glTF 2.0 format',
     'author': 'Julien Duroure, Norbert Nopper, Urs Hanselmann, Moritz Becher, Benjamin Schmithüsen, Jim Eckerlein, and many external contributors',
-    "version": (1, 2, 41),
+    "version": (1, 2, 42),
     'blender': (2, 82, 7),
     'location': 'File > Import-Export',
     'description': 'Import-Export as glTF 2.0',

io_scene_gltf2/blender/exp/gltf2_blender_export.py

@@ -24,6 +24,7 @@ from io_scene_gltf2.blender.exp.gltf2_blender_gltf2_exporter import GlTF2Exporte
 from io_scene_gltf2.io.com.gltf2_io_debug import print_console, print_newline
 from io_scene_gltf2.io.exp import gltf2_io_export
 from io_scene_gltf2.io.exp import gltf2_io_draco_compression_extension
+from io_scene_gltf2.io.exp.gltf2_io_user_extensions import export_user_extensions
 
 
 def save(context, export_settings):
@@ -61,6 +62,10 @@ def __export(export_settings):
 def __gather_gltf(exporter, export_settings):
     active_scene_idx, scenes, animations = gltf2_blender_gather.gather_gltf2(export_settings)
 
+    plan = {'active_scene_idx': active_scene_idx, 'scenes': scenes, 'animations': animations}
+    export_user_extensions('gather_gltf_hook', export_settings, plan)
+    active_scene_idx, scenes, animations = plan['active_scene_idx'], plan['scenes'], plan['animations']
+
     if export_settings['gltf_draco_mesh_compression']:
         gltf2_io_draco_compression_extension.compress_scene_primitives(scenes, export_settings)
         exporter.add_draco_extension()

io_scene_gltf2/io/exp/gltf2_io_user_extensions.py

@@ -12,11 +12,16 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-def export_user_extensions(hook_name, export_settings, gltf2_object, *args):
-    if gltf2_object.extensions is None:
-        gltf2_object.extensions = {}
+def export_user_extensions(hook_name, export_settings, *args):
+    if args and hasattr(args[0], "extensions"):
+        if args[0].extensions is None:
+            args[0].extensions = {}
 
     for extension in export_settings['gltf_user_extensions']:
         hook = getattr(extension, hook_name, None)
         if hook is not None:
-            hook(gltf2_object, *args, export_settings)
+            try:
+                hook(*args, export_settings)
+            except Exception as e:
+                print(hook_name, "fails on", extension)
+                print(str(e))