fix: StaticArrayVal payload encoding, improve roundtrip checker

hugr-py/src/hugr/std/collections/static_array.py

@@ -55,8 +55,8 @@ def to_value(self) -> val.Extension:
         # into specialized `Value`s).
         serial_val = {
             "value": {
-                "values": [v._to_serial_root().model_dump_json() for v in self.v],
-                "typ": self.ty.ty._to_serial_root().model_dump_json(),
+                "values": [v._to_serial_root() for v in self.v],
+                "typ": self.ty.ty._to_serial_root(),
             },
             "name": self.name,
         }

hugr-py/tests/conftest.py

@@ -10,6 +10,7 @@
 from typing_extensions import Self
 
 from hugr import ext, tys
+from hugr._serialization import ops as sops
 from hugr.envelope import EnvelopeConfig
 from hugr.hugr import Hugr
 from hugr.ops import AsExtOp, Command, Const, Custom, DataflowOp, ExtOp, RegisteredOp
@@ -262,14 +263,18 @@ def _hash_node(cls, h: Hugr, n: Node, depth: int, name: str) -> _NodeHash:
         elif isinstance(op_type, Const):
             # We need every custom value to have the same repr if they compare
             # equal. For example, an `IntVal(42)` should be the same as the
-            # equivalent `Extension` value.
-            # This needs a lot of extra unwrapping, since each class implements
-            # different `__repr__` methods.
+            # equivalent `Extension` value. This needs a lot of extra
+            # unwrapping, since each class implements different `__repr__`
+            # methods.
             #
-            # Our solution here is to roundtrip via `sops.Value`. This may miss
-            # some errors, but it's the best we can do for now.
-            serial_val = op_type.val._to_serial_root()
-            val = serial_val.deserialize()
+            # Our solution here is to roundtrip via JSON. This may miss some
+            # errors, but it's the best we can do for now. Note that
+            # roundtripping via `sops.Value` is not enough, since nested
+            # specialized values don't get serialized straight away. (e.g.
+            # StaticArrayVal's dictionary payload containing a SumValue
+            # internally, see `test_val_static_array`).
+            value_dict = op_type.val._to_serial_root().model_dump()
+            val = sops.Value(**value_dict).deserialize()
             op = repr(Const(val, num_out=op_type.num_out))
         else:
             op = op_type.name()