"""
Provide a serialization API.
"""
from __future__ import annotations
from typing import TypeVar, Sequence, Mapping, overload, Literal, TypeAlias, Any
[docs]
class Void:
"""
A sentinel that describes the absence of a value.
Using this sentinel allows for actual values to be ``None``. Like ``None``,
``Void`` is only ever used through its type, and never instantiated.
"""
[docs]
def __new__(cls): # pragma: no cover # noqa D102
raise RuntimeError("The Void sentinel cannot be instantiated.")
#: The Python types that define a serialized dump.
DumpType: TypeAlias = bool | int | float | str | None | list["Dump"] | dict[str, "Dump"]
_DumpTypeT = TypeVar("_DumpTypeT", bound=DumpType)
#: A serialized dump.
Dump: TypeAlias = (
bool | int | float | str | None | Sequence["Dump"] | Mapping[str, "Dump"]
)
_DumpT = TypeVar("_DumpT", bound=Dump)
_DumpU = TypeVar("_DumpU", bound=Dump)
#: A serialized dump that may be :py:class:`betty.serde.dump.Void`.
VoidableDump: TypeAlias = Dump | type[Void]
_VoidableDumpT = TypeVar("_VoidableDumpT", bound=VoidableDump)
_VoidableDumpU = TypeVar("_VoidableDumpU", bound=VoidableDump)
#: A dump which is a list whose values are serialized dumps.
ListDump: TypeAlias = list[_DumpT]
#: A dump which is a dictionary whose keys are strings and values are serialized dumps.
DictDump: TypeAlias = dict[str, _DumpT]
#: A dump which is a list whose values are serialized dumps, or that may be :py:class:`betty.serde.dump.Void`
VoidableListDump: TypeAlias = list[_VoidableDumpU]
#: A dump which is a dictionary whose keys are strings and values are serialized dumps, or that may be :py:class:`betty.serde.dump.Void`
VoidableDictDump: TypeAlias = dict[str, _VoidableDumpU]
_MinimizableDump: TypeAlias = (
VoidableDump | VoidableListDump[_VoidableDumpU] | VoidableDictDump[_VoidableDumpU]
)
@overload
def minimize(
dump: _MinimizableDump[VoidableDump], voidable: Literal[True] = True
) -> VoidableDump:
pass # pragma: no cover
@overload
def minimize(dump: _MinimizableDump[VoidableDump], voidable: Literal[False]) -> Dump:
pass # pragma: no cover
[docs]
def minimize(
dump: _MinimizableDump[VoidableDump], voidable: bool = True
) -> VoidableDump:
"""
Minimize a configuration dump by removing any Void configurationfrom sequences and mappings.
"""
if isinstance(dump, (Sequence, Mapping)) and not isinstance(dump, str):
if isinstance(dump, Sequence):
dump = [value for value in dump if value is not Void]
for key in reversed(range(len(dump))):
if dump[key] is Void:
del dump[key]
if isinstance(dump, Mapping):
dump = {key: value for key, value in dump.items() if value is not Void}
if len(dump) or not voidable:
return dump # type: ignore[return-value]
return Void
return dump
[docs]
def void_none(value: VoidableDump) -> VoidableDump:
"""
Passthrough a value, but convert Void to None.
"""
return Void if value is None else value
[docs]
def none_void(value: VoidableDump) -> VoidableDump:
"""
Passthrough a value, but convert None to Void.
"""
return None if value is Void else value
[docs]
def dump_default(dump, key, default_type):
"""
Add a key and value to a dump, if the key does not exist yet.
"""
try:
assert isinstance(dump[key], default_type)
except KeyError:
dump[key] = default_type()
return dump[key] # type: ignore[return-value]
[docs]
class Dumpable:
"""
Instances can be dumped to serializable data.
"""
[docs]
def dump(self) -> VoidableDump:
"""
Dump this instance to a portable format.
"""
raise NotImplementedError(repr(self))