Enhance nativescript.py type hint (#129)

* UPDATE. including nativescript.py module in mypy test

* UPDATE. ensure NativeScript.from_primitive() only handles list inputs

UPDATE. improve to_dict() type hint

UPDATE. improve to_dict() conditional readability

* UPDATE. InvalidBefore and InvalidHereAfter should not have optional before and after fields

* UPDATE. letting mypy know to_cbor() value is bytes

* UPDATE. mypy cannot detect common attributes in a list of classes

* UPDATE. mypy cannot infer the second argument of super() is NativeScript class' subclass

* UPDATE. explicitly assigning NativeScript subclass instantiation type by individual conditional check

UPDATE. simplify from_dict() method

UPDATE. create a JSON_TAG_TO_INT map

Author: daehan-koreapool

pycardano/nativescript.py

@@ -3,7 +3,7 @@
 from __future__ import annotations
 
 from dataclasses import dataclass, field
-from typing import ClassVar, List, Type, Union
+from typing import ClassVar, List, Type, Union, cast
 
 from nacl.encoding import RawEncoder
 from nacl.hash import blake2b
@@ -35,25 +35,37 @@ def from_primitive(
     ) -> Union[
         ScriptPubkey, ScriptAll, ScriptAny, ScriptNofK, InvalidBefore, InvalidHereAfter
     ]:
-        script_type = value[0]
-        for t in [
-            ScriptPubkey,
-            ScriptAll,
-            ScriptAny,
-            ScriptNofK,
-            InvalidBefore,
-            InvalidHereAfter,
-        ]:
-            if t._TYPE == script_type:
-                return super(NativeScript, t).from_primitive(value[1:])
+        if not isinstance(
+            value,
+            (
+                list,
+                tuple,
+            ),
+        ):
+            raise DeserializeException(
+                f"A list or a tuple is required for deserialization: {str(value)}"
+            )
+
+        script_type: int = value[0]
+        if script_type == ScriptPubkey._TYPE:
+            return super(NativeScript, ScriptPubkey).from_primitive(value[1:])
+        elif script_type == ScriptAll._TYPE:
+            return super(NativeScript, ScriptAll).from_primitive(value[1:])
+        elif script_type == ScriptAny._TYPE:
+            return super(NativeScript, ScriptAny).from_primitive(value[1:])
+        elif script_type == ScriptNofK._TYPE:
+            return super(NativeScript, ScriptNofK).from_primitive(value[1:])
+        elif script_type == InvalidBefore._TYPE:
+            return super(NativeScript, InvalidBefore).from_primitive(value[1:])
+        elif script_type == InvalidHereAfter._TYPE:
+            return super(NativeScript, InvalidHereAfter).from_primitive(value[1:])
         else:
             raise DeserializeException(f"Unknown script type indicator: {script_type}")
 
     def hash(self) -> ScriptHash:
+        cbor_bytes = cast(bytes, self.to_cbor("bytes"))
         return ScriptHash(
-            blake2b(
-                bytes(1) + self.to_cbor("bytes"), SCRIPT_HASH_SIZE, encoder=RawEncoder
-            )
+            blake2b(bytes(1) + cbor_bytes, SCRIPT_HASH_SIZE, encoder=RawEncoder)
         )
 
     @classmethod
@@ -63,43 +75,16 @@ def from_dict(
         ScriptPubkey, ScriptAll, ScriptAny, ScriptNofK, InvalidBefore, InvalidHereAfter
     ]:
         """Parse a standard native script dictionary (potentially parsed from a JSON file)."""
-
-        types = {
-            p.json_tag: p
-            for p in [
-                ScriptPubkey,
-                ScriptAll,
-                ScriptAny,
-                ScriptNofK,
-                InvalidBefore,
-                InvalidHereAfter,
-            ]
-        }
-        script_type = script_json["type"]
-        target_class = types[script_type]
         script_primitive = cls._script_json_to_primitive(script_json)
-        return super(NativeScript, target_class).from_primitive(script_primitive[1:])
+        return cls.from_primitive(script_primitive)
 
     @classmethod
     def _script_json_to_primitive(
         cls: Type[NativeScript], script_json: JsonDict
     ) -> List[Primitive]:
         """Serialize a standard JSON native script into a primitive array"""
-
-        types = {
-            p.json_tag: p
-            for p in [
-                ScriptPubkey,
-                ScriptAll,
-                ScriptAny,
-                ScriptNofK,
-                InvalidBefore,
-                InvalidHereAfter,
-            ]
-        }
-
         script_type: str = script_json["type"]
-        native_script = [types[script_type]._TYPE]
+        native_script: List[Primitive] = [JSON_TAG_TO_INT[script_type]]
 
         for key, value in script_json.items():
             if key == "type":
@@ -118,22 +103,18 @@ def _script_jsons_to_primitive(
         native_script = [cls._script_json_to_primitive(i) for i in script_jsons]
         return native_script
 
-    def to_dict(self) -> dict:
+    def to_dict(self) -> JsonDict:
         """Export to standard native script dictionary (potentially to dump to a JSON file)."""
-
-        script = {}
-
+        script: JsonDict = {}
         for value in self.__dict__.values():
             script["type"] = self.json_tag
 
             if isinstance(value, list):
                 script["scripts"] = [i.to_dict() for i in value]
-
+            elif isinstance(value, int):
+                script[self.json_field] = value
             else:
-                if isinstance(value, int):
-                    script[self.json_field] = value
-                else:
-                    script[self.json_field] = str(value)
+                script[self.json_field] = str(value)
 
         return script
 
@@ -209,7 +190,7 @@ class InvalidBefore(NativeScript):
     json_field: ClassVar[str] = "slot"
     _TYPE: int = field(default=4, init=False)
 
-    before: int = None
+    before: int
 
 
 @dataclass
@@ -218,4 +199,14 @@ class InvalidHereAfter(NativeScript):
     json_field: ClassVar[str] = "slot"
     _TYPE: int = field(default=5, init=False)
 
-    after: int = None
+    after: int
+
+
+JSON_TAG_TO_INT = {
+    ScriptPubkey.json_tag: ScriptPubkey._TYPE,
+    ScriptAll.json_tag: ScriptAll._TYPE,
+    ScriptAny.json_tag: ScriptAny._TYPE,
+    ScriptNofK.json_tag: ScriptNofK._TYPE,
+    InvalidBefore.json_tag: InvalidBefore._TYPE,
+    InvalidHereAfter.json_tag: InvalidHereAfter._TYPE,
+}

pyproject.toml

@@ -75,7 +75,6 @@ exclude = [
     '^pycardano/key.py$',
     '^pycardano/logging.py$',
     '^pycardano/metadata.py$',
-    '^pycardano/nativescript.py$',
     '^pycardano/plutus.py$',
     '^pycardano/transaction.py$',
     '^pycardano/txbuilder.py$',

test/pycardano/test_nativescript.py

@@ -2,7 +2,7 @@
 
 import pytest
 
-from pycardano.exception import InvalidArgumentException
+from pycardano.exception import DeserializeException, InvalidArgumentException
 from pycardano.key import VerificationKey
 from pycardano.nativescript import (
     InvalidBefore,
@@ -163,6 +163,11 @@ def test_to_dict():
     assert NativeScript.from_dict(script_dict) == script_nofk
 
 
+def test_from_primitive_invalid_primitive_input():
+    with pytest.raises(DeserializeException):
+        NativeScript.from_primitive(1)
+
+
 def test_from_dict():
 
     vk1 = VerificationKey.from_cbor(