_yaml.py: Added node_copy() and list_copy()

These are similar to node_chain_copy() and node_list_copy() which
are there mostly for optimization reasons, but node_copy() and
list_copy() entirely safely separate the nodes from their originals.

This is suitable when giving away a node to a plugin via an API
call where we want to be sure that no modifications modify the source
node.

As a side effect it also ensures that ever node has Provenance, in case
nodes are given back to the data model where they might be expected later.

1 files changed, 30 insertions, 0 deletions

diff --git a/buildstream/_yaml.py b/buildstream/_yaml.py
index 93fae4903..c8151d501 100644
--- a/buildstream/_yaml.py
+++ b/buildstream/_yaml.py
@@ -602,3 +602,33 @@ def list_chain_copy(source):
             copy.append(item)
 
     return copy
+
+
+def node_copy(source):
+    copy = {}
+    for key, value in source.items():
+        if isinstance(value, collections.Mapping):
+            copy[key] = node_copy(value)
+        elif isinstance(value, list):
+            copy[key] = list_copy(value)
+        elif isinstance(value, Provenance):
+            copy[key] = value.clone()
+
+    ensure_provenance(copy)
+
+    return copy
+
+
+def list_copy(source):
+    copy = []
+    for item in source:
+        if isinstance(item, collections.Mapping):
+            copy.append(node_copy(item))
+        elif isinstance(item, list):
+            copy.append(list_copy(item))
+        elif isinstance(item, Provenance):
+            copy.append(item.clone())
+        else:
+            copy.append(item)
+
+    return copy