Cleanup internal Loader cache after loading elements

1 files changed, 19 insertions, 0 deletions

diff --git a/buildstream/_loader/loader.py b/buildstream/_loader/loader.py
index d0cfa8522..17d7c63fb 100644
--- a/buildstream/_loader/loader.py
+++ b/buildstream/_loader/loader.py
@@ -152,8 +152,27 @@ class Loader():
             #
             ret.append(loader._collect_element(element))
 
+        self._clean_caches()
+
         return ret
 
+    # clean_caches()
+    #
+    # Clean internal loader caches, recursively
+    #
+    # When loading the elements, the loaders use caches in order to not load the
+    # same element twice. These are kept after loading and prevent garbage
+    # collection. Cleaning them explicitely is required.
+    #
+    def _clean_caches(self):
+        for loader in self._loaders.values():
+            # value may be None with nested junctions without overrides
+            if loader is not None:
+                loader._clean_caches()
+
+        self._meta_elements = {}
+        self._elements = {}
+
     ###########################################
     #            Private Methods              #
     ###########################################