Fix pickling for pypy

capnp/lib/capnp.pyx

@@ -845,7 +845,10 @@ cdef class _MessageSize:
         self.word_count = word_count
         self.cap_count = cap_count
 
-def _struct_reducer(schema_id, data):
+if getattr(_sys, 'subversion', [''])[0] == 'PyPy':
+    from pickle_helper import _struct_reducer
+else:
+    def _struct_reducer(schema_id, data):
         return _global_schema_parser.modules_by_id[schema_id].from_bytes(data)
 
 cdef class _DynamicStructReader:
@@ -930,7 +933,7 @@ cdef class _DynamicStructReader:
             size = self.thisptr.totalSize()
             return _MessageSize(size.wordCount, size.capCount)
 
-    def __reduce__(self):
+    def __reduce_ex__(self, proto):
         return _struct_reducer, (self.schema.node.id, self.as_builder().to_bytes())
 
 cdef class _DynamicStructBuilder:
@@ -1191,7 +1194,7 @@ cdef class _DynamicStructBuilder:
             size = self.thisptr.totalSize()
             return _MessageSize(size.wordCount, size.capCount)
 
-    def __reduce__(self):
+    def __reduce_ex__(self, proto):
         return _struct_reducer, (self.schema.node.id, self.to_bytes())
 
 cdef class _DynamicStructPipeline:

capnp/lib/pickle_helper.py

@@ -0,0 +1,6 @@
+import capnp
+
+
+def _struct_reducer(schema_id, data):
+    'Hack to deal with pypy not allowing reduce functions to be "built-in" methods (ie. compiled from a .pyx)'
+    return capnp._global_schema_parser.modules_by_id[schema_id].from_bytes(data)