feat(nano): use more custom classes with faux protection

hathor/nanocontracts/faux_immutable.py

@@ -18,6 +18,10 @@
 
 from typing_extensions import ParamSpec
 
+# special attrs:
+SKIP_VALIDATION_ATTR: str = '__skip_faux_immutability_validation__'
+ALLOW_INHERITANCE_ATTR: str = '__allow_faux_inheritance__'
+
 
 def _validate_faux_immutable_meta(name: str, bases: tuple[type, ...], attrs: dict[str, object]) -> None:
     """Run validations during faux-immutable class creation."""
@@ -37,18 +41,25 @@ def _validate_faux_immutable_meta(name: str, bases: tuple[type, ...], attrs: dic
         '__call__',
     })
 
+    # pop the attribute so the created class doesn't have it and it isn't inherited
+    allow_inheritance = attrs.pop(ALLOW_INHERITANCE_ATTR, False)
+
     # Prohibit all other dunder attributes/methods.
     for attr in attrs:
         if '__' in attr and attr not in required_attrs | allowed_dunder:
             raise TypeError(f'faux-immutable class `{name}` must not define `{attr}`')
 
     # Prohibit inheritance on faux-immutable classes, this may be less strict in the future,
-    # but we may only allow bases where `type(base) is _FauxImmutableMeta`.
-    if len(bases) != 1 or not bases[0] is FauxImmutable:
+    # but we may only allow bases where `type(base) is FauxImmutableMeta`.
+    if len(bases) != 1:
+        raise TypeError('faux-immutable only allows one base')
+
+    base, = bases
+    if base is not FauxImmutable and not allow_inheritance:
         raise TypeError(f'faux-immutable class `{name}` must inherit from `FauxImmutable` only')
 
 
-class _FauxImmutableMeta(type):
+class FauxImmutableMeta(type):
     """
     A metaclass for faux-immutable classes.
     This means the class objects themselves are immutable, that is, `__setattr__` always raises AttributeError.
@@ -60,15 +71,15 @@ def __new__(cls, name, bases, attrs, **kwargs):
         # validations are just a sanity check to make sure we only apply this metaclass to classes
         # that will actually become immutable, for example, using this metaclass doesn't provide
         # complete faux-immutability if the class doesn't define `__slots__`.
-        if not attrs.get('__skip_faux_immutability_validation__', False):
+        if not attrs.get(SKIP_VALIDATION_ATTR, False):
             _validate_faux_immutable_meta(name, bases, attrs)
         return super().__new__(cls, name, bases, attrs, **kwargs)
 
     def __setattr__(cls, name: str, value: object) -> None:
         raise AttributeError(f'cannot set attribute `{name}` on faux-immutable class')
 
 
-class FauxImmutable(metaclass=_FauxImmutableMeta):
+class FauxImmutable(metaclass=FauxImmutableMeta):
     """
     Utility superclass for creating faux-immutable classes.
     Simply inherit from it to define a faux-immutable class.

hathor/nanocontracts/nc_types/bytes_nc_type.py

@@ -49,7 +49,7 @@ def _from_type(cls, type_: type[B], /, *, type_map: NCType.TypeMap) -> Self:
     @override
     def _check_value(self, value: bytes, /, *, deep: bool) -> None:
         if isclass(self._actual_type):
-            if not isinstance(value, self._actual_type):
+            if not isinstance(value, (bytes, self._actual_type)):
                 raise TypeError('expected {self._actual_type} instance')
         else:
             if not isinstance(value, bytes):

hathor/nanocontracts/types.py

@@ -17,7 +17,7 @@
 import inspect
 from dataclasses import dataclass
 from enum import Enum, unique
-from typing import Any, Callable, Generic, NewType, TypeAlias, TypeVar
+from typing import Any, Callable, Generic, TypeAlias, TypeVar
 
 from typing_extensions import override
 
@@ -28,28 +28,60 @@
     validate_method_types,
 )
 from hathor.nanocontracts.exception import BlueprintSyntaxError, NCSerializationError
+from hathor.nanocontracts.faux_immutable import FauxImmutableMeta
 from hathor.transaction.util import bytes_to_int, int_to_bytes
 from hathor.utils.typing import InnerTypeMixin
 
+# XXX: mypy gives the following errors on all subclasses of `bytes` that use FauxImmutableMeta:
+#
+# Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its
+# bases
+#
+# However `bytes` metaclass appears to be `type` (just like `int`'s) and `FauxImmutableMeta` correctly inherits from
+# `type`, so it seems like it's a mypy error.
+
 
 # Types to be used by blueprints.
-class Address(bytes):
+class Address(bytes, metaclass=FauxImmutableMeta):  # type: ignore[misc]
+    __allow_faux_inheritance__ = True
+    __slots__ = ()
+
+
+class VertexId(bytes, metaclass=FauxImmutableMeta):  # type: ignore[misc]
+    __slots__ = ()
+    __allow_faux_inheritance__ = True
+
+
+class BlueprintId(VertexId):  # type: ignore[misc]
+    __slots__ = ()
+    __allow_faux_inheritance__ = True
+
+
+class ContractId(VertexId):  # type: ignore[misc]
+    __slots__ = ()
+    __allow_faux_inheritance__ = True
+
+
+class TokenUid(bytes, metaclass=FauxImmutableMeta):  # type: ignore[misc]
+    __slots__ = ()
+    __allow_faux_inheritance__ = True
+
+
+class TxOutputScript(bytes, metaclass=FauxImmutableMeta):  # type: ignore[misc]
     __slots__ = ()
+    __allow_faux_inheritance__ = True
 
 
-class VertexId(bytes):
+class Amount(int, metaclass=FauxImmutableMeta):
     __slots__ = ()
+    __allow_faux_inheritance__ = True
 
 
-class ContractId(VertexId):
+class Timestamp(int, metaclass=FauxImmutableMeta):
     __slots__ = ()
+    __allow_faux_inheritance__ = True
 
 
-Amount = NewType('Amount', int)
-Timestamp = NewType('Timestamp', int)
-TokenUid = NewType('TokenUid', bytes)
-TxOutputScript = NewType('TxOutputScript', bytes)
-BlueprintId = NewType('BlueprintId', VertexId)
 CallerId: TypeAlias = Address | ContractId
 
 T = TypeVar('T')

tests/nanocontracts/test_exposed_properties.py

@@ -44,94 +44,6 @@
     'hathor.nanocontracts.exception.NCFail.args',
     'hathor.nanocontracts.exception.NCFail.some_new_attribute',
     'hathor.nanocontracts.exception.NCFail.with_traceback',
-    'hathor.nanocontracts.types.Address.capitalize',
-    'hathor.nanocontracts.types.Address.center',
-    'hathor.nanocontracts.types.Address.count',
-    'hathor.nanocontracts.types.Address.decode',
-    'hathor.nanocontracts.types.Address.endswith',
-    'hathor.nanocontracts.types.Address.expandtabs',
-    'hathor.nanocontracts.types.Address.find',
-    'hathor.nanocontracts.types.Address.fromhex',
-    'hathor.nanocontracts.types.Address.hex',
-    'hathor.nanocontracts.types.Address.index',
-    'hathor.nanocontracts.types.Address.isalnum',
-    'hathor.nanocontracts.types.Address.isalpha',
-    'hathor.nanocontracts.types.Address.isascii',
-    'hathor.nanocontracts.types.Address.isdigit',
-    'hathor.nanocontracts.types.Address.islower',
-    'hathor.nanocontracts.types.Address.isspace',
-    'hathor.nanocontracts.types.Address.istitle',
-    'hathor.nanocontracts.types.Address.isupper',
-    'hathor.nanocontracts.types.Address.join',
-    'hathor.nanocontracts.types.Address.ljust',
-    'hathor.nanocontracts.types.Address.lower',
-    'hathor.nanocontracts.types.Address.lstrip',
-    'hathor.nanocontracts.types.Address.maketrans',
-    'hathor.nanocontracts.types.Address.partition',
-    'hathor.nanocontracts.types.Address.removeprefix',
-    'hathor.nanocontracts.types.Address.removesuffix',
-    'hathor.nanocontracts.types.Address.replace',
-    'hathor.nanocontracts.types.Address.rfind',
-    'hathor.nanocontracts.types.Address.rindex',
-    'hathor.nanocontracts.types.Address.rjust',
-    'hathor.nanocontracts.types.Address.rpartition',
-    'hathor.nanocontracts.types.Address.rsplit',
-    'hathor.nanocontracts.types.Address.rstrip',
-    'hathor.nanocontracts.types.Address.some_new_attribute',
-    'hathor.nanocontracts.types.Address.split',
-    'hathor.nanocontracts.types.Address.splitlines',
-    'hathor.nanocontracts.types.Address.startswith',
-    'hathor.nanocontracts.types.Address.strip',
-    'hathor.nanocontracts.types.Address.swapcase',
-    'hathor.nanocontracts.types.Address.title',
-    'hathor.nanocontracts.types.Address.translate',
-    'hathor.nanocontracts.types.Address.upper',
-    'hathor.nanocontracts.types.Address.zfill',
-    'hathor.nanocontracts.types.Amount.some_new_attribute',
-    'hathor.nanocontracts.types.BlueprintId.some_new_attribute',
-    'hathor.nanocontracts.types.ContractId.capitalize',
-    'hathor.nanocontracts.types.ContractId.center',
-    'hathor.nanocontracts.types.ContractId.count',
-    'hathor.nanocontracts.types.ContractId.decode',
-    'hathor.nanocontracts.types.ContractId.endswith',
-    'hathor.nanocontracts.types.ContractId.expandtabs',
-    'hathor.nanocontracts.types.ContractId.find',
-    'hathor.nanocontracts.types.ContractId.fromhex',
-    'hathor.nanocontracts.types.ContractId.hex',
-    'hathor.nanocontracts.types.ContractId.index',
-    'hathor.nanocontracts.types.ContractId.isalnum',
-    'hathor.nanocontracts.types.ContractId.isalpha',
-    'hathor.nanocontracts.types.ContractId.isascii',
-    'hathor.nanocontracts.types.ContractId.isdigit',
-    'hathor.nanocontracts.types.ContractId.islower',
-    'hathor.nanocontracts.types.ContractId.isspace',
-    'hathor.nanocontracts.types.ContractId.istitle',
-    'hathor.nanocontracts.types.ContractId.isupper',
-    'hathor.nanocontracts.types.ContractId.join',
-    'hathor.nanocontracts.types.ContractId.ljust',
-    'hathor.nanocontracts.types.ContractId.lower',
-    'hathor.nanocontracts.types.ContractId.lstrip',
-    'hathor.nanocontracts.types.ContractId.maketrans',
-    'hathor.nanocontracts.types.ContractId.partition',
-    'hathor.nanocontracts.types.ContractId.removeprefix',
-    'hathor.nanocontracts.types.ContractId.removesuffix',
-    'hathor.nanocontracts.types.ContractId.replace',
-    'hathor.nanocontracts.types.ContractId.rfind',
-    'hathor.nanocontracts.types.ContractId.rindex',
-    'hathor.nanocontracts.types.ContractId.rjust',
-    'hathor.nanocontracts.types.ContractId.rpartition',
-    'hathor.nanocontracts.types.ContractId.rsplit',
-    'hathor.nanocontracts.types.ContractId.rstrip',
-    'hathor.nanocontracts.types.ContractId.some_new_attribute',
-    'hathor.nanocontracts.types.ContractId.split',
-    'hathor.nanocontracts.types.ContractId.splitlines',
-    'hathor.nanocontracts.types.ContractId.startswith',
-    'hathor.nanocontracts.types.ContractId.strip',
-    'hathor.nanocontracts.types.ContractId.swapcase',
-    'hathor.nanocontracts.types.ContractId.title',
-    'hathor.nanocontracts.types.ContractId.translate',
-    'hathor.nanocontracts.types.ContractId.upper',
-    'hathor.nanocontracts.types.ContractId.zfill',
     'hathor.nanocontracts.types.NCAcquireAuthorityAction.melt',
     'hathor.nanocontracts.types.NCAcquireAuthorityAction.mint',
     'hathor.nanocontracts.types.NCAcquireAuthorityAction.name',
@@ -204,52 +116,6 @@
     'hathor.nanocontracts.types.SignedData.checksig',
     'hathor.nanocontracts.types.SignedData.get_data_bytes',
     'hathor.nanocontracts.types.SignedData.some_new_attribute',
-    'hathor.nanocontracts.types.Timestamp.some_new_attribute',
-    'hathor.nanocontracts.types.TokenUid.some_new_attribute',
-    'hathor.nanocontracts.types.TxOutputScript.some_new_attribute',
-    'hathor.nanocontracts.types.VertexId.capitalize',
-    'hathor.nanocontracts.types.VertexId.center',
-    'hathor.nanocontracts.types.VertexId.count',
-    'hathor.nanocontracts.types.VertexId.decode',
-    'hathor.nanocontracts.types.VertexId.endswith',
-    'hathor.nanocontracts.types.VertexId.expandtabs',
-    'hathor.nanocontracts.types.VertexId.find',
-    'hathor.nanocontracts.types.VertexId.fromhex',
-    'hathor.nanocontracts.types.VertexId.hex',
-    'hathor.nanocontracts.types.VertexId.index',
-    'hathor.nanocontracts.types.VertexId.isalnum',
-    'hathor.nanocontracts.types.VertexId.isalpha',
-    'hathor.nanocontracts.types.VertexId.isascii',
-    'hathor.nanocontracts.types.VertexId.isdigit',
-    'hathor.nanocontracts.types.VertexId.islower',
-    'hathor.nanocontracts.types.VertexId.isspace',
-    'hathor.nanocontracts.types.VertexId.istitle',
-    'hathor.nanocontracts.types.VertexId.isupper',
-    'hathor.nanocontracts.types.VertexId.join',
-    'hathor.nanocontracts.types.VertexId.ljust',
-    'hathor.nanocontracts.types.VertexId.lower',
-    'hathor.nanocontracts.types.VertexId.lstrip',
-    'hathor.nanocontracts.types.VertexId.maketrans',
-    'hathor.nanocontracts.types.VertexId.partition',
-    'hathor.nanocontracts.types.VertexId.removeprefix',
-    'hathor.nanocontracts.types.VertexId.removesuffix',
-    'hathor.nanocontracts.types.VertexId.replace',
-    'hathor.nanocontracts.types.VertexId.rfind',
-    'hathor.nanocontracts.types.VertexId.rindex',
-    'hathor.nanocontracts.types.VertexId.rjust',
-    'hathor.nanocontracts.types.VertexId.rpartition',
-    'hathor.nanocontracts.types.VertexId.rsplit',
-    'hathor.nanocontracts.types.VertexId.rstrip',
-    'hathor.nanocontracts.types.VertexId.some_new_attribute',
-    'hathor.nanocontracts.types.VertexId.split',
-    'hathor.nanocontracts.types.VertexId.splitlines',
-    'hathor.nanocontracts.types.VertexId.startswith',
-    'hathor.nanocontracts.types.VertexId.strip',
-    'hathor.nanocontracts.types.VertexId.swapcase',
-    'hathor.nanocontracts.types.VertexId.title',
-    'hathor.nanocontracts.types.VertexId.translate',
-    'hathor.nanocontracts.types.VertexId.upper',
-    'hathor.nanocontracts.types.VertexId.zfill',
     'hathor.nanocontracts.types.fallback.some_new_attribute',
     'hathor.nanocontracts.types.public.some_new_attribute',
     'hathor.nanocontracts.types.view.some_new_attribute',

tests/nanocontracts/test_faux_immutability.py

@@ -43,7 +43,7 @@ def test_invalid_inheritance() -> None:
     class Super:
         pass
 
-    with pytest.raises(TypeError, match='faux-immutable class `Foo` must inherit from `FauxImmutable` only'):
+    with pytest.raises(TypeError, match='faux-immutable only allows one base'):
         class Foo(FauxImmutable, Super):
             __slots__ = ()
 
@@ -145,80 +145,80 @@ def class_method(cls) -> None:
     # Existing attribute on class
     #
 
-    # protected by _FauxImmutableMeta.__setattr__
+    # protected by FauxImmutableMeta.__setattr__
     with pytest.raises(AttributeError, match='cannot set attribute `attr` on faux-immutable class'):
         Foo.attr = 'bar'
 
-    # protected by _FauxImmutableMeta.__setattr__
+    # protected by FauxImmutableMeta.__setattr__
     with pytest.raises(AttributeError, match='cannot set attribute `attr` on faux-immutable class'):
         setattr(Foo, 'attr', 'bar')
 
     # protected by Python itself
-    with pytest.raises(TypeError, match="can't apply this __setattr__ to _FauxImmutableMeta object"):
+    with pytest.raises(TypeError, match="can't apply this __setattr__ to FauxImmutableMeta object"):
         object.__setattr__(Foo, 'attr', 'bar')
 
     #
     # Existing class attribute on class
     #
 
-    # protected by _FauxImmutableMeta.__setattr__
+    # protected by FauxImmutableMeta.__setattr__
     with pytest.raises(AttributeError, match='cannot set attribute `class_attr` on faux-immutable class'):
         Foo.class_attr = 'bar'
 
-    # protected by _FauxImmutableMeta.__setattr__
+    # protected by FauxImmutableMeta.__setattr__
     with pytest.raises(AttributeError, match='cannot set attribute `class_attr` on faux-immutable class'):
         setattr(Foo, 'class_attr', 'bar')
 
     # protected by Python itself
-    with pytest.raises(TypeError, match="can't apply this __setattr__ to _FauxImmutableMeta object"):
+    with pytest.raises(TypeError, match="can't apply this __setattr__ to FauxImmutableMeta object"):
         object.__setattr__(Foo, 'class_attr', 'bar')
 
     #
     # Existing method on class
     #
 
-    # protected by _FauxImmutableMeta.__setattr__
+    # protected by FauxImmutableMeta.__setattr__
     with pytest.raises(AttributeError, match='cannot set attribute `method` on faux-immutable class'):
         Foo.method = lambda self: None  # type: ignore[method-assign]
 
-    # protected by _FauxImmutableMeta.__setattr__
+    # protected by FauxImmutableMeta.__setattr__
     with pytest.raises(AttributeError, match='cannot set attribute `method` on faux-immutable class'):
         setattr(Foo, 'method', lambda self: None)
 
     # protected by Python itself
-    with pytest.raises(TypeError, match="can't apply this __setattr__ to _FauxImmutableMeta object"):
+    with pytest.raises(TypeError, match="can't apply this __setattr__ to FauxImmutableMeta object"):
         object.__setattr__(Foo, 'method', lambda self: None)
 
     #
     # Existing class method on class
     #
 
-    # protected by _FauxImmutableMeta.__setattr__
+    # protected by FauxImmutableMeta.__setattr__
     with pytest.raises(AttributeError, match='cannot set attribute `class_method` on faux-immutable class'):
         Foo.class_method = lambda: None  # type: ignore[method-assign]
 
-    # protected by _FauxImmutableMeta.__setattr__
+    # protected by FauxImmutableMeta.__setattr__
     with pytest.raises(AttributeError, match='cannot set attribute `class_method` on faux-immutable class'):
         setattr(Foo, 'class_method', lambda self: None)
 
     # protected by Python itself
-    with pytest.raises(TypeError, match="can't apply this __setattr__ to _FauxImmutableMeta object"):
+    with pytest.raises(TypeError, match="can't apply this __setattr__ to FauxImmutableMeta object"):
         object.__setattr__(Foo, 'class_method', lambda self: None)
 
     #
     # New attribute on class
     #
 
-    # protected by _FauxImmutableMeta.__setattr__
+    # protected by FauxImmutableMeta.__setattr__
     with pytest.raises(AttributeError, match='cannot set attribute `new_class_attr` on faux-immutable class'):
         Foo.new_class_attr = 'bar'
 
-    # protected by _FauxImmutableMeta.__setattr__
+    # protected by FauxImmutableMeta.__setattr__
     with pytest.raises(AttributeError, match='cannot set attribute `new_class_attr` on faux-immutable class'):
         setattr(Foo, 'new_class_attr', 'bar')
 
     # protected by Python itself
-    with pytest.raises(TypeError, match="can't apply this __setattr__ to _FauxImmutableMeta object"):
+    with pytest.raises(TypeError, match="can't apply this __setattr__ to FauxImmutableMeta object"):
         object.__setattr__(Foo, 'new_class_attr', 'bar')