7 files changed, 34 insertions, 8 deletions
diff --git a/source/blender/blenkernel/BKE_lib_id.h b/source/blender/blenkernel/BKE_lib_id.h
index 6b706f3bcd0..62a39abf755 100644
--- a/source/blender/blenkernel/BKE_lib_id.h
+++ b/source/blender/blenkernel/BKE_lib_id.h
@@ -201,6 +201,8 @@ enum {
 void BKE_libblock_free_datablock(struct ID *id, const int flag) ATTR_NONNULL();
 void BKE_libblock_free_data(struct ID *id, const bool do_id_user) ATTR_NONNULL();
 
+void BKE_libblock_free_data_py(struct ID *id);
+
 void BKE_id_free_ex(struct Main *bmain, void *idv, int flag, const bool use_flag_from_idtag);
 void BKE_id_free(struct Main *bmain, void *idv);
 
diff --git a/source/blender/blenkernel/intern/gpencil.c b/source/blender/blenkernel/intern/gpencil.c
index 182d06f8f72..13cee6d9e6a 100644
--- a/source/blender/blenkernel/intern/gpencil.c
+++ b/source/blender/blenkernel/intern/gpencil.c
@@ -513,6 +513,7 @@ void BKE_gpencil_eval_delete(bGPdata *gpd_eval)
 {
   BKE_gpencil_free(gpd_eval, true);
   BKE_libblock_free_data(&gpd_eval->id, false);
+  BLI_assert(!gpd_eval->id.py_instance); /* Or call #BKE_libblock_free_data_py. */
   MEM_freeN(gpd_eval);
 }
 
diff --git a/source/blender/blenkernel/intern/lib_id_delete.c b/source/blender/blenkernel/intern/lib_id_delete.c
index 67b2e4429d6..f17c64942d4 100644
--- a/source/blender/blenkernel/intern/lib_id_delete.c
+++ b/source/blender/blenkernel/intern/lib_id_delete.c
@@ -142,14 +142,7 @@ void BKE_id_free_ex(Main *bmain, void *idv, int flag, const bool use_flag_from_i
     DEG_id_type_tag(bmain, type);
   }
 
-#ifdef WITH_PYTHON
-#  ifdef WITH_PYTHON_SAFETY
-  BPY_id_release(id);
-#  endif
-  if (id->py_instance) {
-    BPY_DECREF_RNA_INVALIDATE(id->py_instance);
-  }
-#endif
+  BKE_libblock_free_data_py(id);
 
   Key *key = ((flag & LIB_ID_FREE_NO_MAIN) == 0) ? BKE_key_from_id(id) : NULL;
 
@@ -406,3 +399,29 @@ size_t BKE_id_multi_tagged_delete(Main *bmain)
 {
   return id_delete(bmain, true);
 }
+
+/* -------------------------------------------------------------------- */
+/** \name Python Data Handling
+ * \{ */
+
+/**
+ * In most cases #BKE_id_free_ex handles this, when lower level functions are called directly
+ * this function will need to be called too, if Python has access to the data.
+ *
+ * ID data-blocks such as #Material.nodetree are not stored in #Main.
+ */
+void BKE_libblock_free_data_py(ID *id)
+{
+#ifdef WITH_PYTHON
+#  ifdef WITH_PYTHON_SAFETY
+  BPY_id_release(id);
+#  endif
+  if (id->py_instance) {
+    BPY_DECREF_RNA_INVALIDATE(id->py_instance);
+  }
+#else
+  UNUSED_VARS(id);
+#endif
+}
+
+/** \} */
diff --git a/source/blender/blenkernel/intern/material.c b/source/blender/blenkernel/intern/material.c
index 8e80a4bc9ae..b3e68f97e21 100644
--- a/source/blender/blenkernel/intern/material.c
+++ b/source/blender/blenkernel/intern/material.c
@@ -1662,6 +1662,7 @@ void BKE_material_copybuf_free(void)
 {
   if (matcopybuf.nodetree) {
     ntreeFreeLocalTree(matcopybuf.nodetree);
+    BLI_assert(!matcopybuf.nodetree->id.py_instance); /* Or call #BKE_libblock_free_data_py. */
     MEM_freeN(matcopybuf.nodetree);
     matcopybuf.nodetree = NULL;
   }
diff --git a/source/blender/blenkernel/intern/node.cc b/source/blender/blenkernel/intern/node.cc
index 68ae6963a3e..bb1c3b30880 100644
--- a/source/blender/blenkernel/intern/node.cc
+++ b/source/blender/blenkernel/intern/node.cc
@@ -3020,6 +3020,7 @@ void ntreeFreeEmbeddedTree(bNodeTree *ntree)
 {
   ntreeFreeTree(ntree);
   BKE_libblock_free_data(&ntree->id, true);
+  BKE_libblock_free_data_py(&ntree->id);
 }
 
 void ntreeFreeLocalTree(bNodeTree *ntree)
diff --git a/source/blender/blenkernel/intern/particle_system.c b/source/blender/blenkernel/intern/particle_system.c
index c727a144c87..4260f4fc5e3 100644
--- a/source/blender/blenkernel/intern/particle_system.c
+++ b/source/blender/blenkernel/intern/particle_system.c
@@ -4764,6 +4764,7 @@ static void particle_settings_free_local(ParticleSettings *particle_settings)
 {
   BKE_libblock_free_datablock(&particle_settings->id, 0);
   BKE_libblock_free_data(&particle_settings->id, false);
+  BLI_assert(!particle_settings->id.py_instance); /* Or call #BKE_libblock_free_data_py. */
   MEM_freeN(particle_settings);
 }
 
diff --git a/source/blender/blenkernel/intern/scene.c b/source/blender/blenkernel/intern/scene.c
index a4ab64a8a02..66d4b18fb83 100644
--- a/source/blender/blenkernel/intern/scene.c
+++ b/source/blender/blenkernel/intern/scene.c
@@ -444,6 +444,7 @@ static void scene_free_data(ID *id)
    * collections in the scene need to do it too? */
   if (scene->master_collection) {
     BKE_collection_free(scene->master_collection);
+    BKE_libblock_free_data_py(&scene->master_collection->id);
     MEM_freeN(scene->master_collection);
     scene->master_collection = NULL;
   }