Correctly parse List[X] annotated objects (#170)

* Correctly parse List[X] annotated objects from dictionaries

* Formatting

* Add testcase for data list

* Fix to_json of lists

* Fix parsing List[x] from cbor

* Raise useful exception when encountering wrong type

Author: nielstron

pycardano/plutus.py

@@ -529,16 +529,14 @@ def _dfs(obj):
                 return {"int": obj}
             elif isinstance(obj, bytes):
                 return {"bytes": obj.hex()}
-            elif isinstance(obj, list):
-                return [_dfs(item) for item in obj]
-            elif isinstance(obj, IndefiniteList):
+            elif isinstance(obj, IndefiniteList) or isinstance(obj, list):
                 return {"list": [_dfs(item) for item in obj]}
             elif isinstance(obj, dict):
                 return {"map": [{"v": _dfs(v), "k": _dfs(k)} for k, v in obj.items()]}
             elif isinstance(obj, PlutusData):
                 return {
                     "constructor": obj.CONSTR_ID,
-                    "fields": _dfs([getattr(obj, f.name) for f in fields(obj)]),
+                    "fields": [_dfs(getattr(obj, f.name)) for f in fields(obj)],
                 }
             else:
                 raise TypeError(f"Unexpected type {type(obj)}")
@@ -589,6 +587,25 @@ def _dfs(obj):
                                 raise DeserializeException(
                                     f"Unexpected data structure: {f}."
                                 )
+                        elif (
+                            hasattr(f_info.type, "__origin__")
+                            and f_info.type.__origin__ is list
+                        ):
+                            t_args = f_info.type.__args__
+                            if len(t_args) != 1:
+                                raise DeserializeException(
+                                    f"List types need exactly one type argument, but got {t_args}"
+                                )
+                            if "list" not in f:
+                                raise DeserializeException(
+                                    f'Expected type "list" for constructor List but got {f}'
+                                )
+                            t = t_args[0]
+                            if inspect.isclass(t) and issubclass(t, PlutusData):
+                                converted_fields.append(t.from_dict(f))
+                            else:
+                                converted_fields.append(_dfs(f))
+
                         elif (
                             hasattr(f_info.type, "__origin__")
                             and f_info.type.__origin__ is dict

pycardano/serialization.py

@@ -417,6 +417,19 @@ def _restore_dataclass_field(
         return f.metadata["object_hook"](v)
     elif isclass(f.type) and issubclass(f.type, CBORSerializable):
         return f.type.from_primitive(v)
+    elif hasattr(f.type, "__origin__") and (f.type.__origin__ is list):
+        t_args = f.type.__args__
+        if len(t_args) != 1:
+            raise DeserializeException(
+                f"List types need exactly one type argument, but got {t_args}"
+            )
+        t = t_args[0]
+        if not isinstance(v, list):
+            raise DeserializeException(f"Expected type list but got {type(v)}")
+        if isclass(t) and issubclass(t, CBORSerializable):
+            return IndefiniteList([t.from_primitive(w) for w in v])
+        else:
+            return IndefiniteList(v)
     elif isclass(f.type) and issubclass(f.type, IndefiniteList):
         return IndefiniteList(v)
     elif hasattr(f.type, "__origin__") and (f.type.__origin__ is dict):

test/pycardano/test_plutus.py

@@ -2,7 +2,7 @@
 import unittest
 
 from test.pycardano.util import check_two_way_cbor
-from typing import Union, Dict
+from typing import Union, Dict, List
 
 import pytest
 
@@ -48,6 +48,11 @@ class DictTest(PlutusData):
     a: Dict[int, LargestTest]
 
 
+@dataclass
+class ListTest(PlutusData):
+    a: List[LargestTest]
+
+
 @dataclass
 class VestingParam(PlutusData):
     CONSTR_ID = 1
@@ -104,6 +109,28 @@ def test_plutus_data_json():
     assert my_vesting == VestingParam.from_json(encoded_json)
 
 
+def test_plutus_data_json_list():
+    test = ListTest([LargestTest(), LargestTest()])
+    encoded_json = test.to_json(separators=(",", ":"))
+
+    assert (
+        '{"constructor":0,"fields":[{"list":[{"constructor":9,"fields":[]},{"constructor":9,"fields":[]}]}]}'
+        == encoded_json
+    )
+
+    assert test == ListTest.from_json(encoded_json)
+
+
+def test_plutus_data_cbor_list():
+    test = ListTest([LargestTest(), LargestTest()])
+
+    encoded_cbor = test.to_cbor()
+
+    assert "d8799f82d9050280d9050280ff" == encoded_cbor
+
+    assert test == ListTest.from_cbor(encoded_cbor)
+
+
 def test_plutus_data_json_dict():
     test = DictTest({0: LargestTest(), 1: LargestTest()})