Merge branch 'jennis/compose_backwards' into 'master'

cleanup: Move YAML handling logic in _include.py to _yaml.py

See merge request BuildStream/buildstream!1205

2 files changed, 13 insertions, 6 deletions

diff --git a/buildstream/_includes.py b/buildstream/_includes.py
index 1312d1982..f4a162761 100644
--- a/buildstream/_includes.py
+++ b/buildstream/_includes.py
@@ -82,12 +82,7 @@ class Includes:
                 finally:
                     included.remove(file_path)
 
-                _yaml.composite(include_node, node)
-                to_delete = [key for key, _ in _yaml.node_items(node) if key not in include_node]
-                for key, value in include_node.items():
-                    node[key] = value
-                for key in to_delete:
-                    del node[key]
+                _yaml.composite_and_move(node, include_node)
 
         for _, value in _yaml.node_items(node):
             self._process_value(value,
diff --git a/buildstream/_yaml.py b/buildstream/_yaml.py
index 230094c22..74ed1bbf8 100644
--- a/buildstream/_yaml.py
+++ b/buildstream/_yaml.py
@@ -903,6 +903,18 @@ def composite(target, source):
                                 e.actual_type.__name__)) from e
 
 
+# Like composite(target, source), but where target overrides source instead.
+#
+def composite_and_move(target, source):
+    composite(source, target)
+
+    to_delete = [key for key, _ in node_items(target) if key not in source]
+    for key, value in source.items():
+        target[key] = value
+    for key in to_delete:
+        del target[key]
+
+
 # SanitizedDict is an OrderedDict that is dumped as unordered mapping.
 # This provides deterministic output for unordered mappings.
 #