Bugs: value-object core semantics (0.28.1) #33

Defects in the value-object core of 0.28.1 (each one reproduced). The 1.0.0 core (pyvalueobjects/_core.py) is designed to remove them; every item gets a regression test and is ticked when the fix lands.

• C00 ValueObject.__eq__ raises ValueObjectError when compared with a non-VO: Int(1) == None, Int(2) in [1, Int(2)], Int(1) in {1: 0}, {Int(1), 1} and frozen-dataclass entities with an optional VO all crash. (d8793bf) Fixed in the core (pyvalueobjects/_core.py); the 0.x classes the root still exports keep the old behaviour until their family switches (B3-B9).
• X00 Equality and hashing ignore the type: UserId(x) == OrderId(x), Int(1) == Float(1.0), Int(1) == PositiveInt(1); unrelated VOs collide as dict/set keys. (d8793bf) Fixed in the core (pyvalueobjects/_core.py); the 0.x classes the root still exports keep the old behaviour until their family switches (B3-B9).
• C01 The VO stores and returns the caller's mutable object, so a validated ArrayList(Int) can end up holding 'x'.
• C03 VOs are mutable: _value can be reassigned, attributes added, __init__ re-run in place (corrupts sets/dicts). (833f137, ff48b21, a15af5d) Fixed in the core (pyvalueobjects/_core.py); the 0.x classes the root still exports keep the old behaviour until their family switches (B3-B9).
• C04 ValueObject.__hash__ assumes a hashable value: hash(ArrayList(Int)([1])) raises TypeError.
• C06 ValueObjectError does not call super().__init__: keyword construction gives an empty message and it cannot be pickled/copied. (a0c9ce5)
• X05 from pyvalueobjects.errors import ValueObjectError imports a module, so except ValueObjectError raises TypeError.
• C07 from pyvalueobjects import * exports the subpackage names (numbers, strings, ...) and shadows the stdlib numbers module.
• C02/C15 build_nullable makes NullablePositiveInt(None) an instance of PositiveInt holding None (Liskov violation; x.value() > 0 crashes).
• C05/C17 str_value() of a null VO returns the string 'None', indistinguishable from a real 'None' string.