node: picklable {Scalar,Mapping,Sequence}Node

Make ScalarNode, MappingNode, and SequenceNode pickable by implementing
`__reduce__` for them.

1 files changed, 18 insertions, 0 deletions

diff --git a/src/buildstream/node.pyx b/src/buildstream/node.pyx
index 8a66514e1..ea63151b9 100644
--- a/src/buildstream/node.pyx
+++ b/src/buildstream/node.pyx
@@ -289,6 +289,12 @@ cdef class ScalarNode(Node):
 
         self.value = value
 
+    def __reduce__(self):
+        return (
+            ScalarNode.__new__,
+            (ScalarNode, self.file_index, self.line, self.column, self.value),
+        )
+
     #############################################################
     #                       Public Methods                      #
     #############################################################
@@ -435,6 +441,12 @@ cdef class MappingNode(Node):
     def __cinit__(self, int file_index, int line, int column, dict value):
         self.value = value
 
+    def __reduce__(self):
+        return (
+            MappingNode.__new__,
+            (MappingNode, self.file_index, self.line, self.column, self.value),
+        )
+
     def __contains__(self, what):
         return what in self.value
 
@@ -1078,6 +1090,12 @@ cdef class SequenceNode(Node):
     def __cinit__(self, int file_index, int line, int column, list value):
         self.value = value
 
+    def __reduce__(self):
+        return (
+            SequenceNode.__new__,
+            (SequenceNode, self.file_index, self.line, self.column, self.value),
+        )
+
     def __iter__(self):
         return iter(self.value)