Fix T88033: Python reference memory leaks for non main data-blocks

ID data-blocks that could be accessed from Python and weren't freed
using BKE_id_free_ex did not release the Python reference count.

Add BKE_libblock_free_data_py function to clear the Python reference
in this case.

Add asserts to ensure no Python reference is held in situations
when ID's are copied for internal use (not exposed through the RNA API),
to ensure these kinds of leaks don't go by unnoticed again.

1 files changed, 27 insertions, 8 deletions

diff --git a/source/blender/blenkernel/intern/lib_id_delete.c b/source/blender/blenkernel/intern/lib_id_delete.c
index a9407860c06..43afac5a376 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
+}
+
+/** \} */