fix: .to_message() on Arrays

Related issue: ConsenSysMesh/py-eip712-structs#16

Original patch by @josh-davis-vicinft on ConsenSysMesh/py-eip712-structs#17.

Author: BoboTiG

src/eip712_structs/struct.py

@@ -83,7 +83,14 @@ def data_dict(self) -> dict:
 
         Nested structs instances are also converted to dict form.
         """
-        return {k: v.data_dict() if isinstance(v, EIP712Struct) else v for k, v in self.values.items()}
+        return {
+            k: v.data_dict()
+            if isinstance(v, EIP712Struct)
+            else [e.data_dict() for e in v]
+            if isinstance(v, list) and len(v) and isinstance(v[0], EIP712Struct)
+            else v
+            for k, v in self.values.items()
+        }
 
     @classmethod
     def encode_type(cls, resolve: bool = True) -> str:
@@ -95,7 +102,7 @@ def encode_type(cls, resolve: bool = True) -> str:
         struct_sig = f"{cls.type_name}({','.join(member_sigs)})"
 
         if resolve:
-            reference_structs: set[EIP712Struct] = set()
+            reference_structs: list[EIP712Struct] = []
             cls.gather_reference_structs(reference_structs)
             sorted_structs = sorted((s for s in reference_structs if s != cls), key=lambda s: s.type_name)
             for struct in sorted_structs:
@@ -104,15 +111,17 @@ def encode_type(cls, resolve: bool = True) -> str:
         return struct_sig
 
     @classmethod
-    def gather_reference_structs(cls, struct_set: set[EIP712Struct]) -> None:
+    def gather_reference_structs(cls, struct_lst: list[EIP712Struct]) -> None:
         """Finds reference structs defined in this struct type, and inserts them into the given set."""
-        structs: list[EIP712Struct] = [
-            m[1] for m in cls.get_members() if isinstance(m[1], type) and issubclass(m[1], EIP712Struct)
+        structs = [m[1] for m in cls.get_members() if isinstance(m[1], type) and issubclass(m[1], EIP712Struct)] + [
+            m[1].member_type
+            for m in cls.get_members()
+            if isinstance(m[1], Array) and hasattr(m[1].member_type, "encode_type")
         ]
         for struct in structs:
-            if struct not in struct_set:
-                struct_set.add(struct)
-                struct.gather_reference_structs(struct_set)
+            if struct not in struct_lst:
+                struct_lst.append(struct)  # type: ignore[arg-type]
+                struct.gather_reference_structs(struct_lst)  # type: ignore[union-attr]
 
     @classmethod
     def type_hash(cls) -> bytes:
@@ -159,7 +168,7 @@ def to_message(self, domain: EIP712Struct | None = None) -> dict:
         :returns: This struct + the domain in dict form, structured as specified for EIP712 messages.
         """
         domain = self._assert_domain(domain)
-        structs = {domain, self}
+        structs = [domain, self]
         self.gather_reference_structs(structs)
 
         # Build type dictionary

src/tests/unit/test_message_json.py

@@ -2,7 +2,7 @@
 import os
 
 import pytest
-from eip712_structs import Bytes, EIP712Struct, String, make_domain
+from eip712_structs import Array, Bytes, EIP712Struct, String, make_domain
 
 
 def test_flat_struct_to_message():
@@ -151,3 +151,25 @@ class UnserializableObject:
     foo.values["b"] = obj
     with pytest.raises(TypeError, match="not JSON serializable"):
         foo.to_message_json(domain)
+
+
+def test_array_to_message():
+    class TestStruct(EIP712Struct):
+        byte_array = Array(Bytes(32), 4)
+
+    byte_array = [os.urandom(32) for _ in range(4)]
+
+    domain = make_domain(name="hello")
+    s = TestStruct(byte_array=byte_array)
+
+    msg = s.to_message(domain)
+    assert msg["primaryType"] == "TestStruct"
+    assert msg["types"] == {
+        "EIP712Domain": [{"name": "name", "type": "string"}],
+        "TestStruct": [{"name": "byte_array", "type": "bytes32[4]"}],
+    }
+    assert msg["domain"] == {"name": "hello"}
+    assert msg["message"]["byte_array"]
+    assert isinstance(msg["message"]["byte_array"], list)
+    assert isinstance(msg["message"]["byte_array"][0], bytes)
+    assert isinstance(msg["message"]["byte_array"][-1], bytes)