Add slots to value objects

Author: ivan-borovets

src/app/domain/value_objects/base.py

@@ -33,6 +33,15 @@ def __post_init__(self) -> None:
         Hook for additional initialization and ensuring invariants.
         Subclasses can override this method to implement custom logic, while
         still calling `super().__post_init__()` to preserve base checks.
+
+        Note on slotted dataclasses:
+        With `slots=True`, the dataclass transformation may replace the class
+        object; a zero-arg `super()` in a subclass `__post_init__` can then raise
+        `TypeError`. In such cases, call the base with two-arg super, e.g.:
+            `super(Username, self).__post_init__()`
+        (or invoke directly: `ValueObject.__post_init__(self)`).
+
+        Reference: https://github.com/python/cpython/issues/90562
         """
         self.__forbid_base_class_instantiation()
         self.__check_field_existence()

src/app/domain/value_objects/raw_password.py

@@ -5,7 +5,7 @@
 from app.domain.value_objects.base import ValueObject
 
 
-@dataclass(frozen=True, repr=False)
+@dataclass(frozen=True, slots=True, repr=False)
 class RawPassword(ValueObject):
     """raises DomainFieldError"""
 
@@ -15,7 +15,7 @@ class RawPassword(ValueObject):
 
     def __post_init__(self) -> None:
         """:raises DomainFieldError:"""
-        super().__post_init__()
+        super(RawPassword, self).__post_init__()
         self._validate_password_length(self.value)
 
     def _validate_password_length(self, password_value: str) -> None:

src/app/domain/value_objects/user_id.py

@@ -4,6 +4,6 @@
 from app.domain.value_objects.base import ValueObject
 
 
-@dataclass(frozen=True, repr=False)
+@dataclass(frozen=True, slots=True, repr=False)
 class UserId(ValueObject):
     value: UUID

src/app/domain/value_objects/user_password_hash.py

@@ -3,6 +3,6 @@
 from app.domain.value_objects.base import ValueObject
 
 
-@dataclass(frozen=True, repr=False)
+@dataclass(frozen=True, slots=True, repr=False)
 class UserPasswordHash(ValueObject):
     value: bytes

src/app/domain/value_objects/username.py

@@ -6,7 +6,7 @@
 from app.domain.value_objects.base import ValueObject
 
 
-@dataclass(frozen=True, repr=False)
+@dataclass(frozen=True, slots=True, repr=False)
 class Username(ValueObject):
     """raises DomainFieldError"""
 
@@ -35,7 +35,7 @@ class Username(ValueObject):
 
     def __post_init__(self) -> None:
         """:raises DomainFieldError:"""
-        super().__post_init__()
+        super(Username, self).__post_init__()
         self._validate_username_length(self.value)
         self._validate_username_pattern(self.value)
 

tests/app/unit/factories/named_entity.py

@@ -4,7 +4,7 @@
 from app.domain.value_objects.base import ValueObject
 
 
-@dataclass(frozen=True, repr=False)
+@dataclass(frozen=True, slots=True, repr=False)
 class NamedEntityId(ValueObject):
     value: int
 

tests/app/unit/factories/tagged_entity.py

@@ -4,7 +4,7 @@
 from app.domain.value_objects.base import ValueObject
 
 
-@dataclass(frozen=True, repr=False)
+@dataclass(frozen=True, slots=True, repr=False)
 class TaggedEntityId(ValueObject):
     value: int
 

tests/app/unit/factories/value_objects.py

@@ -9,12 +9,12 @@
 from app.domain.value_objects.username import Username
 
 
-@dataclass(frozen=True, repr=False)
+@dataclass(frozen=True, slots=True, repr=False)
 class SingleFieldVO(ValueObject):
     value: int
 
 
-@dataclass(frozen=True, repr=False)
+@dataclass(frozen=True, slots=True, repr=False)
 class MultiFieldVO(ValueObject):
     value1: int
     value2: str