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confingy.serde#

serde #

SerializationKeys #

Constants for serialization markers in the serialized data.

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class SerializationKeys:
    """Constants for serialization markers in the serialized data."""

    CLASS = "_confingy_class"
    MODULE = "_confingy_module"
    LAZY = "_confingy_lazy"
    CONFIG = "_confingy_config"
    INIT = "_confingy_init"
    DATACLASS = "_confingy_dataclass"
    FIELDS = "_confingy_fields"
    CALLABLE = "_confingy_callable"
    TRACKED_INFO = "_confingy_tracked_info"
    UNSERIALIZABLE = "_confingy_unserializable"
    OBJECT = "_confingy_object"
    METHOD = "_confingy_method"
    NAME = "_confingy_name"
    CLASS_HASH = "_confingy_class_hash"
    ENUM = "_confingy_enum"
    TUPLE = "_confingy_tuple"
    SET = "_confingy_set"
    FROZENSET = "_confingy_frozenset"
    NAMEDTUPLE = "_confingy_namedtuple"
    DICT = "_confingy_dict"
    ITEMS = "_confingy_items"

SerializationHandler #

Bases: ABC

Abstract base class for serialization handlers.

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class SerializationHandler(ABC):
    """Abstract base class for serialization handlers."""

    @abstractmethod
    def can_handle(self, obj: Any) -> bool:
        """Check if this handler can serialize the given object."""
        pass

    @abstractmethod
    def serialize(self, obj: Any, context: "SerializationContext") -> Any:
        """Serialize the object."""
        pass

    @abstractmethod
    def deserialize(self, data: Any, context: "DeserializationContext") -> Any:
        """Deserialize the data."""
        pass

    def map_children(self, obj: Any, fn: "Callable[[Any], Any]") -> Any:
        """Apply fn to all child values, returning new object with transformed children.

        This enables recursive traversal of nested structures for operations like
        lens/unlens without duplicating container-specific logic.

        Default returns obj unchanged (for leaf types like primitives).
        """
        return obj

can_handle abstractmethod #

can_handle(obj: Any) -> bool

Check if this handler can serialize the given object.

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@abstractmethod
def can_handle(self, obj: Any) -> bool:
    """Check if this handler can serialize the given object."""
    pass

serialize abstractmethod #

serialize(obj: Any, context: SerializationContext) -> Any

Serialize the object.

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@abstractmethod
def serialize(self, obj: Any, context: "SerializationContext") -> Any:
    """Serialize the object."""
    pass

deserialize abstractmethod #

deserialize(
    data: Any, context: DeserializationContext
) -> Any

Deserialize the data.

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@abstractmethod
def deserialize(self, data: Any, context: "DeserializationContext") -> Any:
    """Deserialize the data."""
    pass

map_children #

map_children(obj: Any, fn: Callable[[Any], Any]) -> Any

Apply fn to all child values, returning new object with transformed children.

This enables recursive traversal of nested structures for operations like lens/unlens without duplicating container-specific logic.

Default returns obj unchanged (for leaf types like primitives).

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def map_children(self, obj: Any, fn: "Callable[[Any], Any]") -> Any:
    """Apply fn to all child values, returning new object with transformed children.

    This enables recursive traversal of nested structures for operations like
    lens/unlens without duplicating container-specific logic.

    Default returns obj unchanged (for leaf types like primitives).
    """
    return obj

SerializationContext #

Context for serialization operations.

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class SerializationContext:
    """Context for serialization operations."""

    def __init__(self):
        self.handlers: list[SerializationHandler] = []
        self._depth = 0
        self._max_depth = 100
        self._path: list[str] = []  # Track object path for debugging

    def register_handler(self, handler: SerializationHandler):
        """Register a serialization handler."""
        self.handlers.append(handler)

    def serialize(self, obj: Any, key: str | None = None) -> Any:
        """Serialize an object using registered handlers."""
        if key:
            self._path.append(key)

        self._depth += 1
        try:
            if self._depth > self._max_depth:
                path_str = " -> ".join(self._path)
                raise SerializationError(
                    f"Maximum recursion depth ({self._max_depth}) exceeded at path: {path_str}"
                )

            for handler in self.handlers:
                if handler.can_handle(obj):
                    return handler.serialize(obj, self)

            # Raise an error for unserializable objects
            path_str = " -> ".join(self._path) if self._path else "root"
            raise SerializationError(
                f"No handler found for type {type(obj).__name__} at path {path_str}"
            )
        except Exception as e:
            if not isinstance(e, SerializationError):
                path_str = " -> ".join(self._path) if self._path else "root"
                raise SerializationError(
                    f"Failed to serialize at path {path_str}: {e}"
                ) from e
            raise
        finally:
            self._depth -= 1
            if key:
                self._path.pop()

register_handler #

register_handler(handler: SerializationHandler)

Register a serialization handler.

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def register_handler(self, handler: SerializationHandler):
    """Register a serialization handler."""
    self.handlers.append(handler)

serialize #

serialize(obj: Any, key: str | None = None) -> Any

Serialize an object using registered handlers.

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def serialize(self, obj: Any, key: str | None = None) -> Any:
    """Serialize an object using registered handlers."""
    if key:
        self._path.append(key)

    self._depth += 1
    try:
        if self._depth > self._max_depth:
            path_str = " -> ".join(self._path)
            raise SerializationError(
                f"Maximum recursion depth ({self._max_depth}) exceeded at path: {path_str}"
            )

        for handler in self.handlers:
            if handler.can_handle(obj):
                return handler.serialize(obj, self)

        # Raise an error for unserializable objects
        path_str = " -> ".join(self._path) if self._path else "root"
        raise SerializationError(
            f"No handler found for type {type(obj).__name__} at path {path_str}"
        )
    except Exception as e:
        if not isinstance(e, SerializationError):
            path_str = " -> ".join(self._path) if self._path else "root"
            raise SerializationError(
                f"Failed to serialize at path {path_str}: {e}"
            ) from e
        raise
    finally:
        self._depth -= 1
        if key:
            self._path.pop()

DeserializationContext #

Context for deserialization operations.

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class DeserializationContext:
    """Context for deserialization operations."""

    def __init__(self, strict: bool = True):
        """Initialize deserialization context.

        Args:
            strict: If True (default), raise an error when serialized configs contain
                kwargs that no longer exist in the class signature. If False, emit
                a warning and ignore the extra kwargs. Similar to PyTorch's
                load_state_dict strict parameter.
        """
        self.handlers: list[SerializationHandler] = []
        self._depth = 0
        self._max_depth = 100
        self.strict = strict

    def register_handler(self, handler: SerializationHandler):
        """Register a serialization handler."""
        self.handlers.append(handler)

    def deserialize(self, data: Any, expected_type: type | None = None) -> Any:
        """Deserialize data using registered handlers."""
        self._depth += 1
        try:
            if self._depth > self._max_depth:
                raise DeserializationError(
                    f"Maximum recursion depth ({self._max_depth}) exceeded"
                )

            # Primitives pass through
            if data is None or isinstance(data, int | float | str | bool):
                return data

            # Try all handlers (including collection handlers)
            for handler in self.handlers:
                result = handler.deserialize(data, self)
                if result is not None:
                    return result

            return data
        finally:
            self._depth -= 1

__init__ #

__init__(strict: bool = True)

Initialize deserialization context.

Parameters:

Name Type Description Default
strict bool

If True (default), raise an error when serialized configs contain kwargs that no longer exist in the class signature. If False, emit a warning and ignore the extra kwargs. Similar to PyTorch's load_state_dict strict parameter.

 True
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def __init__(self, strict: bool = True):
    """Initialize deserialization context.

    Args:
        strict: If True (default), raise an error when serialized configs contain
            kwargs that no longer exist in the class signature. If False, emit
            a warning and ignore the extra kwargs. Similar to PyTorch's
            load_state_dict strict parameter.
    """
    self.handlers: list[SerializationHandler] = []
    self._depth = 0
    self._max_depth = 100
    self.strict = strict

register_handler #

register_handler(handler: SerializationHandler)

Register a serialization handler.

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def register_handler(self, handler: SerializationHandler):
    """Register a serialization handler."""
    self.handlers.append(handler)

deserialize #

deserialize(
    data: Any, expected_type: type | None = None
) -> Any

Deserialize data using registered handlers.

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def deserialize(self, data: Any, expected_type: type | None = None) -> Any:
    """Deserialize data using registered handlers."""
    self._depth += 1
    try:
        if self._depth > self._max_depth:
            raise DeserializationError(
                f"Maximum recursion depth ({self._max_depth}) exceeded"
            )

        # Primitives pass through
        if data is None or isinstance(data, int | float | str | bool):
            return data

        # Try all handlers (including collection handlers)
        for handler in self.handlers:
            result = handler.deserialize(data, self)
            if result is not None:
                return result

        return data
    finally:
        self._depth -= 1

PrimitiveHandler #

Bases: SerializationHandler

Handler for primitive types.

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class PrimitiveHandler(SerializationHandler):
    """Handler for primitive types."""

    def can_handle(self, obj: Any) -> bool:
        return obj is None or isinstance(obj, int | float | str | bool)

    def serialize(self, obj: Any, context: SerializationContext) -> Any:
        return obj

    def deserialize(self, data: Any, context: DeserializationContext) -> Any:
        if self.can_handle(data):
            return data
        return None

EnumHandler #

Bases: SerializationHandler

Handler for enum types.

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class EnumHandler(SerializationHandler):
    """Handler for enum types."""

    def can_handle(self, obj: Any) -> bool:
        return isinstance(obj, enum.Enum)

    def serialize(self, obj: Any, context: SerializationContext) -> dict[str, Any]:
        cls = type(obj)
        return {
            SerializationKeys.CLASS: get_class_name(cls),
            SerializationKeys.MODULE: get_module_name(cls),
            SerializationKeys.ENUM: True,
            SerializationKeys.NAME: obj.name,
        }

    def deserialize(self, data: Any, context: DeserializationContext) -> Any:
        if not isinstance(data, dict):
            return None

        if not data.get(SerializationKeys.ENUM):
            return None

        if SerializationKeys.CLASS not in data or SerializationKeys.MODULE not in data:
            return None

        try:
            cls = import_qualname(
                data[SerializationKeys.MODULE], data[SerializationKeys.CLASS]
            )
            return cls[data[SerializationKeys.NAME]]
        except (ImportError, AttributeError, KeyError) as e:
            raise DeserializationError(
                f"Could not recreate enum {data[SerializationKeys.MODULE]}.{data[SerializationKeys.CLASS]}.{data.get(SerializationKeys.NAME)}: {e}"
            ) from None

PathHandler #

Bases: SerializationHandler

Handler for pathlib paths.

Concrete paths (Path, PosixPath, WindowsPath) are written as Path, so they load as the concrete path type of the reading platform. Pure paths keep their exact class, since PurePosixPath and PureWindowsPath can be created on any platform.

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class PathHandler(SerializationHandler):
    """Handler for pathlib paths.

    Concrete paths (`Path`, `PosixPath`, `WindowsPath`) are written as `Path`, so
    they load as the concrete path type of the reading platform. Pure paths keep
    their exact class, since `PurePosixPath` and `PureWindowsPath` can be created
    on any platform.
    """

    _PATH_CLASSES = (
        "Path",
        "PosixPath",
        "WindowsPath",
        "PurePath",
        "PurePosixPath",
        "PureWindowsPath",
    )

    def can_handle(self, obj: Any) -> bool:
        return isinstance(obj, PurePath)

    def serialize(self, obj: Any, context: SerializationContext) -> dict[str, Any]:
        return {
            SerializationKeys.CLASS: "Path"
            if isinstance(obj, Path)
            else type(obj).__name__,
            SerializationKeys.MODULE: "pathlib",
            SerializationKeys.NAME: str(obj),
        }

    def deserialize(self, data: Any, context: DeserializationContext) -> Any:
        if not isinstance(data, dict):
            return None
        if data.get(SerializationKeys.CLASS) not in self._PATH_CLASSES:
            return None
        if data.get(SerializationKeys.MODULE) != "pathlib":
            return None
        name = data.get(SerializationKeys.NAME, "")
        class_name = data[SerializationKeys.CLASS]
        if class_name in ("PurePath", "PurePosixPath", "PureWindowsPath"):
            return getattr(pathlib, class_name)(name)
        return Path(name)

DatetimeHandler #

Bases: SerializationHandler

Handler for datetime stdlib leaf types.

Covers datetime.date, datetime.datetime, datetime.time, and datetime.timedelta. Serialized as a leaf using the same {_confingy_class, _confingy_module, _confingy_name} envelope as :class:PathHandler.

Wire formats::

date       -> {"_confingy_class": "date",      "_confingy_module": "datetime", "_confingy_name": "2024-01-01"}
datetime   -> {"_confingy_class": "datetime",  "_confingy_module": "datetime", "_confingy_name": "2024-01-01T12:34:56+00:00"}
time       -> {"_confingy_class": "time",      "_confingy_module": "datetime", "_confingy_name": "12:34:56"}
timedelta  -> {"_confingy_class": "timedelta", "_confingy_module": "datetime", "_confingy_name": 93784.0}

date / datetime / time use isoformat() / fromisoformat(). Exact round-trip is guaranteed for values that isoformat() itself emits on the same Python version (the only values we ever feed back in).

timedelta uses total_seconds() (float) for the wire value because the stdlib has no timedelta.fromisoformat. A float can't hold microsecond resolution for very long durations (roughly 100,000 days and up), so those are written as an exact decimal string of seconds (e.g. "8640000000.000001") instead. Both forms are accepted when reading.

Dispatch is by exact type(obj) rather than isinstance because datetime.datetime subclasses datetime.date — a naive isinstance check would mis-serialize datetimes as dates.

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class DatetimeHandler(SerializationHandler):
    """Handler for ``datetime`` stdlib leaf types.

    Covers ``datetime.date``, ``datetime.datetime``, ``datetime.time``, and
    ``datetime.timedelta``. Serialized as a leaf using the same
    ``{_confingy_class, _confingy_module, _confingy_name}`` envelope as
    :class:`PathHandler`.

    Wire formats::

        date       -> {"_confingy_class": "date",      "_confingy_module": "datetime", "_confingy_name": "2024-01-01"}
        datetime   -> {"_confingy_class": "datetime",  "_confingy_module": "datetime", "_confingy_name": "2024-01-01T12:34:56+00:00"}
        time       -> {"_confingy_class": "time",      "_confingy_module": "datetime", "_confingy_name": "12:34:56"}
        timedelta  -> {"_confingy_class": "timedelta", "_confingy_module": "datetime", "_confingy_name": 93784.0}

    ``date`` / ``datetime`` / ``time`` use ``isoformat()`` / ``fromisoformat()``.
    Exact round-trip is guaranteed for values that ``isoformat()`` itself emits
    on the same Python version (the only values we ever feed back in).

    ``timedelta`` uses ``total_seconds()`` (float) for the wire value because the
    stdlib has no ``timedelta.fromisoformat``. A float can't hold microsecond
    resolution for very long durations (roughly 100,000 days and up), so those
    are written as an exact decimal string of seconds (e.g.
    ``"8640000000.000001"``) instead. Both forms are accepted when reading.

    Dispatch is by exact ``type(obj)`` rather than ``isinstance`` because
    ``datetime.datetime`` subclasses ``datetime.date`` — a naive isinstance
    check would mis-serialize datetimes as dates.
    """

    # Map of exact stdlib type -> (wire class name) used for both directions.
    _TYPES = {
        datetime.datetime: "datetime",
        datetime.date: "date",
        datetime.time: "time",
        datetime.timedelta: "timedelta",
    }

    def can_handle(self, obj: Any) -> bool:
        return type(obj) in self._TYPES

    def serialize(self, obj: Any, context: SerializationContext) -> dict[str, Any]:
        cls = type(obj)
        if cls is datetime.timedelta:
            name: Any = obj.total_seconds()
            if datetime.timedelta(seconds=name) != obj:
                name = _timedelta_to_decimal_string(obj)
        else:
            name = obj.isoformat()
        return {
            SerializationKeys.CLASS: self._TYPES[cls],
            SerializationKeys.MODULE: "datetime",
            SerializationKeys.NAME: name,
        }

    def deserialize(self, data: Any, context: DeserializationContext) -> Any:
        if not isinstance(data, dict):
            return None
        if data.get(SerializationKeys.MODULE) != "datetime":
            return None
        class_name = data.get(SerializationKeys.CLASS)
        name = data.get(SerializationKeys.NAME)
        if class_name in ("date", "datetime", "time"):
            if not isinstance(name, str):
                return None
            if class_name == "date":
                return datetime.date.fromisoformat(name)
            if class_name == "datetime":
                return datetime.datetime.fromisoformat(name)
            return datetime.time.fromisoformat(name)
        if class_name == "timedelta":
            if isinstance(name, bool) or not isinstance(name, (int, float, str)):
                return None
            if isinstance(name, str):
                try:
                    seconds = decimal.Decimal(name)
                except decimal.InvalidOperation:
                    return None
                microseconds = int((seconds * 1_000_000).to_integral_value())
                return datetime.timedelta(microseconds=microseconds)
            return datetime.timedelta(seconds=float(name))
        return None

LazyHandler #

Bases: SerializationHandler

Handler for Lazy objects.

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class LazyHandler(SerializationHandler):
    """Handler for Lazy objects."""

    def can_handle(self, obj: Any) -> bool:
        return hasattr(obj, "_confingy_lazy_info")

    def serialize(self, obj: Any, context: SerializationContext) -> dict[str, Any]:
        result = {
            SerializationKeys.CLASS: obj._confingy_lazy_info["class"],
            SerializationKeys.MODULE: obj._confingy_lazy_info["module"],
            SerializationKeys.LAZY: True,
            SerializationKeys.CONFIG: {
                k: context.serialize(v, k) for k, v in obj._confingy_config.items()
            },
        }
        # Include class_hash if available
        if "class_hash" in obj._confingy_lazy_info:
            result[SerializationKeys.CLASS_HASH] = obj._confingy_lazy_info["class_hash"]
        return result

    def deserialize(self, data: dict[str, Any], context: DeserializationContext) -> Any:
        # Only handle dictionaries
        if not isinstance(data, dict):
            return None

        if not (
            data.get(SerializationKeys.LAZY)
            and SerializationKeys.CLASS in data
            and SerializationKeys.MODULE in data
        ):
            return None

        try:
            cls = import_qualname(
                data[SerializationKeys.MODULE], data[SerializationKeys.CLASS]
            )
            actual_cls = getattr(cls, "_original_cls", cls)

            config = {
                k: context.deserialize(v)
                for k, v in data.get(SerializationKeys.CONFIG, {}).items()
            }

            # Filter out extra kwargs that no longer exist in the class signature
            config = _filter_extra_kwargs(
                actual_cls,
                config,
                context.strict,
                f"{data[SerializationKeys.MODULE]}.{data[SerializationKeys.CLASS]}",
            )

            return Lazy(
                actual_cls, config, skip_validation=True, _skip_post_config_hook=True
            )
        except (ImportError, AttributeError) as e:
            raise DeserializationError(
                f"Could not recreate {data[SerializationKeys.MODULE]}.{data[SerializationKeys.CLASS]}: {e}"
            ) from None

TrackedInstanceHandler #

Bases: SerializationHandler

Handler for tracked objects.

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class TrackedInstanceHandler(SerializationHandler):
    """Handler for tracked objects."""

    def can_handle(self, obj: Any) -> bool:
        return hasattr(obj, "_tracked_info")

    def serialize(self, obj: Any, context: SerializationContext) -> dict[str, Any]:
        info = obj._tracked_info
        result = {
            SerializationKeys.CLASS: info["class"],
            SerializationKeys.MODULE: info["module"],
            SerializationKeys.INIT: {
                k: context.serialize(v, k) for k, v in info["init_args"].items()
            },
        }
        # Include class_hash if available
        if "class_hash" in info:
            result[SerializationKeys.CLASS_HASH] = info["class_hash"]
        return result

    def deserialize(self, data: dict[str, Any], context: DeserializationContext) -> Any:
        # Only handle dictionaries
        if not isinstance(data, dict):
            return None

        if (
            SerializationKeys.INIT not in data
            or SerializationKeys.CLASS not in data
            or SerializationKeys.MODULE not in data
        ):
            return None

        try:
            cls = import_qualname(
                data[SerializationKeys.MODULE], data[SerializationKeys.CLASS]
            )
            actual_cls = getattr(cls, "_original_cls", cls)

            init_args = {
                k: context.deserialize(v)
                for k, v in data[SerializationKeys.INIT].items()
            }

            # Filter out extra kwargs that no longer exist in the class signature
            init_args = _filter_extra_kwargs(
                actual_cls,
                init_args,
                context.strict,
                f"{data[SerializationKeys.MODULE]}.{data[SerializationKeys.CLASS]}",
            )

            # Use _create_tracked_instance to add tracking info to the instance
            # without globally modifying the class. This allows re-serialization
            # even if the class wasn't decorated with @track.
            return _create_tracked_instance(actual_cls, (), init_args, _validate=False)
        except (ImportError, AttributeError) as e:
            raise DeserializationError(
                f"Could not recreate {data[SerializationKeys.MODULE]}.{data[SerializationKeys.CLASS]}: {e}"
            ) from None

TypeHandler #

Bases: SerializationHandler

Handler for type objects.

Source code in src/confingy/serde.py 
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class TypeHandler(SerializationHandler):
    """Handler for type objects."""

    def can_handle(self, obj: Any) -> bool:
        return isinstance(obj, type)

    def serialize(self, obj: Any, context: SerializationContext) -> dict[str, Any]:
        # Check if the class can be imported
        if (
            hasattr(obj, "__module__")
            and hasattr(obj, "__qualname__")
            and (
                # Ensure it's not a local or lambda class
                "<locals>" not in obj.__qualname__
                and "<lambda>" not in obj.__qualname__
            )
        ):
            return {
                SerializationKeys.CLASS: "type",
                SerializationKeys.MODULE: get_module_name(obj),
                SerializationKeys.NAME: obj.__qualname__,
            }

        # Raise error for unserializable types
        raise SerializationError(
            f"Cannot serialize type {obj!r}: local or lambda types are not serializable. "
            f"Define the class at module level to make it serializable."
        )

    def deserialize(self, data: dict[str, Any], context: DeserializationContext) -> Any:
        # Only handle dictionaries
        if not isinstance(data, dict):
            return None

        # Check if this is a type serialization
        if data.get(SerializationKeys.CLASS) != "type":
            return None

        # Import and return the type
        if SerializationKeys.MODULE in data and SerializationKeys.NAME in data:
            try:
                module = importlib.import_module(data[SerializationKeys.MODULE])
                parts = data[SerializationKeys.NAME].split(".")
                obj = module
                for part in parts:
                    obj = getattr(obj, part)
                return obj
            except (ImportError, AttributeError) as e:
                raise DeserializationError(
                    f"Could not import type {data[SerializationKeys.MODULE]}.{data[SerializationKeys.NAME]}: {e}"
                ) from None

        return None

CallableHandler #

Bases: SerializationHandler

Handler for callable objects.

Source code in src/confingy/serde.py 
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class CallableHandler(SerializationHandler):
    """Handler for callable objects."""

    def can_handle(self, obj: Any) -> bool:
        return callable(obj) and not isinstance(obj, type)

    def serialize(self, obj: Any, context: SerializationContext) -> dict[str, Any]:
        # Handle methods bound to an instance. The instance is serialized along
        # with the method name. Methods bound to a class (classmethods) or a
        # module (builtins) are importable by qualified name, like functions.
        bound_to = getattr(obj, "__self__", None)
        if bound_to is not None and not isinstance(bound_to, type | types.ModuleType):
            try:
                serialized_object = context.serialize(bound_to, "bound_object")
            except SerializationError as e:
                raise SerializationError(
                    f"Cannot serialize bound method {obj!r}: the object it is bound "
                    f"to is not serializable. Use @track on its class. ({e})"
                ) from None
            return {
                SerializationKeys.CALLABLE: "method",
                SerializationKeys.OBJECT: serialized_object,
                SerializationKeys.METHOD: obj.__name__,
            }

        # Handle standalone functions
        if (
            hasattr(obj, "__module__")
            and hasattr(obj, "__qualname__")
            and (
                "<locals>" not in obj.__qualname__
                and "<lambda>" not in obj.__qualname__
            )
        ):
            return {
                SerializationKeys.CALLABLE: "function",
                SerializationKeys.MODULE: get_module_name(obj),
                SerializationKeys.NAME: obj.__qualname__,
            }

        raise SerializationError(
            f"Cannot serialize callable {obj!r}: lambdas and local functions are not serializable. "
            f"Define the function at module level to make it serializable."
        )

    def deserialize(self, data: dict[str, Any], context: DeserializationContext) -> Any:
        # Only handle dictionaries
        if not isinstance(data, dict):
            return None

        if SerializationKeys.CALLABLE not in data:
            return None

        # Handle serializable callables
        if data[SerializationKeys.CALLABLE] == "function":
            try:
                module = importlib.import_module(data[SerializationKeys.MODULE])
                parts = data[SerializationKeys.NAME].split(".")
                obj = module
                for part in parts:
                    obj = getattr(obj, part)
                return obj
            except (ImportError, AttributeError) as e:
                raise DeserializationError(
                    f"Could not import function {data[SerializationKeys.MODULE]}.{data[SerializationKeys.NAME]}: {e}"
                ) from None

        elif data[SerializationKeys.CALLABLE] == "method":
            obj = context.deserialize(data[SerializationKeys.OBJECT])
            try:
                return getattr(obj, data[SerializationKeys.METHOD])
            except AttributeError as e:
                raise DeserializationError(
                    f"Could not recreate method {data[SerializationKeys.METHOD]}: {e}"
                ) from None

        else:
            raise DeserializationError(
                f"Unknown callable type: {data[SerializationKeys.CALLABLE]}"
            )

CollectionHandler #

Bases: SerializationHandler

Handler for collections (lists, tuples, namedtuples, sets, frozensets, dicts).

Source code in src/confingy/serde.py 
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class CollectionHandler(SerializationHandler):
    """Handler for collections (lists, tuples, namedtuples, sets, frozensets, dicts)."""

    def can_handle(self, obj: Any) -> bool:
        return isinstance(obj, list | tuple | set | frozenset | dict)

    def serialize(self, obj: Any, context: SerializationContext) -> Any:
        if isinstance(obj, tuple) and _is_importable_namedtuple(obj):
            cls = type(obj)
            return {
                SerializationKeys.CLASS: get_class_name(cls),
                SerializationKeys.MODULE: get_module_name(cls),
                SerializationKeys.NAMEDTUPLE: True,
                SerializationKeys.FIELDS: {
                    name: context.serialize(value, name)
                    for name, value in zip(cast(Any, obj)._fields, obj)
                },
            }
        elif isinstance(obj, tuple):
            # Plain tuples, and namedtuples defined inside functions, which can't
            # be imported again
            return {
                SerializationKeys.TUPLE: True,
                SerializationKeys.ITEMS: [
                    context.serialize(item, f"[{i}]") for i, item in enumerate(obj)
                ],
            }
        elif isinstance(obj, set | frozenset):
            items = [context.serialize(item, f"[{i}]") for i, item in enumerate(obj)]
            # Set iteration order depends on PYTHONHASHSEED, so sort for output
            # that is the same across processes
            items.sort(key=lambda item: json.dumps(item, sort_keys=True))
            marker = (
                SerializationKeys.SET
                if isinstance(obj, set)
                else SerializationKeys.FROZENSET
            )
            return {marker: True, SerializationKeys.ITEMS: items}
        elif isinstance(obj, list):
            return [context.serialize(item, f"[{i}]") for i, item in enumerate(obj)]
        elif isinstance(obj, dict):
            if all(isinstance(k, str) and not k.startswith("_confingy_") for k in obj):
                return {k: context.serialize(v, k) for k, v in obj.items()}
            # JSON object keys must be strings, and keys starting with
            # "_confingy_" would be read back as markers, so store other dicts as
            # a list of [key, value] pairs.
            return {
                SerializationKeys.DICT: True,
                SerializationKeys.ITEMS: [
                    [context.serialize(k, f"[{k!r}]"), context.serialize(v, f"[{k!r}]")]
                    for k, v in obj.items()
                ],
            }

    def deserialize(self, data: Any, context: DeserializationContext) -> Any:
        if isinstance(data, list):
            return [context.deserialize(item) for item in data]
        elif isinstance(data, dict):
            # Handle tuple wrapper
            if data.get(SerializationKeys.TUPLE) is True:
                return tuple(
                    context.deserialize(item)
                    for item in data.get(SerializationKeys.ITEMS, [])
                )
            # Handle set wrapper
            elif data.get(SerializationKeys.SET) is True:
                return {
                    context.deserialize(item)
                    for item in data.get(SerializationKeys.ITEMS, [])
                }
            elif data.get(SerializationKeys.FROZENSET) is True:
                return frozenset(
                    context.deserialize(item)
                    for item in data.get(SerializationKeys.ITEMS, [])
                )
            elif data.get(SerializationKeys.NAMEDTUPLE) is True:
                return self._deserialize_namedtuple(data, context)
            # Handle dicts stored as [key, value] pairs
            elif data.get(SerializationKeys.DICT) is True:
                return {
                    context.deserialize(k): context.deserialize(v)
                    for k, v in data.get(SerializationKeys.ITEMS, [])
                }
            # Only handle regular dicts, not confingy special objects
            elif not any(k.startswith("_confingy_") for k in data):
                return {k: context.deserialize(v) for k, v in data.items()}
        return None

    def _deserialize_namedtuple(
        self, data: dict[str, Any], context: DeserializationContext
    ) -> Any:
        try:
            cls = import_qualname(
                data[SerializationKeys.MODULE], data[SerializationKeys.CLASS]
            )
            fields = {
                k: context.deserialize(v)
                for k, v in data.get(SerializationKeys.FIELDS, {}).items()
            }
            return cls(**fields)
        except (ImportError, AttributeError, KeyError, TypeError) as e:
            raise DeserializationError(
                f"Could not recreate namedtuple {data.get(SerializationKeys.MODULE)}."
                f"{data.get(SerializationKeys.CLASS)}: {e}"
            ) from None

    def map_children(self, obj: Any, fn: Callable[[Any], Any]) -> Any:
        children = container_children(obj)
        if children is None:
            return obj
        # Always returns a new container, of the same type as obj (including
        # namedtuples and dict subclasses like defaultdict)
        return rebuild_container(obj, [fn(child) for _, child in children])

DataclassHandler #

Bases: SerializationHandler

Handler for dataclass objects.

Source code in src/confingy/serde.py 
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class DataclassHandler(SerializationHandler):
    """Handler for dataclass objects."""

    def can_handle(self, obj: Any) -> bool:
        return dataclasses.is_dataclass(obj) and not isinstance(obj, type)

    def serialize(self, obj: Any, context: SerializationContext) -> dict[str, Any]:
        cls = obj.__class__
        return {
            SerializationKeys.CLASS: get_class_name(cls),
            SerializationKeys.MODULE: get_module_name(cls),
            SerializationKeys.DATACLASS: True,
            # init=False fields are derived (e.g. in __post_init__) and can't be
            # passed to the constructor, so they aren't part of the config
            SerializationKeys.FIELDS: {
                field.name: context.serialize(getattr(obj, field.name), field.name)
                for field in dataclasses.fields(obj)
                if field.init
            },
        }

    def deserialize(self, data: dict[str, Any], context: DeserializationContext) -> Any:
        # Only handle dictionaries
        if not isinstance(data, dict):
            return None

        if not (
            data.get(SerializationKeys.DATACLASS)
            and SerializationKeys.FIELDS in data
            and SerializationKeys.CLASS in data
            and SerializationKeys.MODULE in data
        ):
            return None

        try:
            cls = import_qualname(
                data[SerializationKeys.MODULE], data[SerializationKeys.CLASS]
            )

            # Deserialize field values. init=False fields, which older versions
            # serialized, are skipped since the constructor doesn't accept them.
            non_init = {f.name for f in dataclasses.fields(cls) if not f.init}
            field_values = {
                k: context.deserialize(v)
                for k, v in data[SerializationKeys.FIELDS].items()
                if k not in non_init
            }

            # Create the dataclass instance
            return cls(**field_values)
        except (ImportError, AttributeError, TypeError) as e:
            raise DeserializationError(
                f"Could not recreate dataclass {data[SerializationKeys.MODULE]}.{data[SerializationKeys.CLASS]}: {e}"
            ) from None

    def map_children(self, obj: Any, fn: Callable[[Any], Any]) -> Any:
        if not (dataclasses.is_dataclass(obj) and not isinstance(obj, type)):
            return obj
        changes = {}
        for field in dataclasses.fields(obj):
            # Skip init=False fields - dataclasses.replace() can't handle them
            if not field.init:
                continue
            old_value = getattr(obj, field.name)
            new_value = fn(old_value)
            if new_value is not old_value:
                changes[field.name] = new_value
        if changes:
            return dataclasses.replace(obj, **changes)
        return obj

HandlerRegistry #

Central registry for serialization and deserialization handlers.

Source code in src/confingy/serde.py 
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class HandlerRegistry:
    """Central registry for serialization and deserialization handlers."""

    @staticmethod
    def get_default_handlers():
        """Get the default set of handlers in the correct order."""
        return [
            PathHandler(),  # Must be before PrimitiveHandler (Path is not a primitive)
            EnumHandler(),  # Must be before PrimitiveHandler (StrEnum/IntEnum are str/int)
            DatetimeHandler(),  # Must be before PrimitiveHandler (datetime types are leaves, not primitives)
            PrimitiveHandler(),
            LazyHandler(),
            TrackedInstanceHandler(),
            DataclassHandler(),
            TypeHandler(),  # Handle type objects before callables
            CallableHandler(),
            CollectionHandler(),
        ]

get_default_handlers staticmethod #

get_default_handlers()

Get the default set of handlers in the correct order.

Source code in src/confingy/serde.py 
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@staticmethod
def get_default_handlers():
    """Get the default set of handlers in the correct order."""
    return [
        PathHandler(),  # Must be before PrimitiveHandler (Path is not a primitive)
        EnumHandler(),  # Must be before PrimitiveHandler (StrEnum/IntEnum are str/int)
        DatetimeHandler(),  # Must be before PrimitiveHandler (datetime types are leaves, not primitives)
        PrimitiveHandler(),
        LazyHandler(),
        TrackedInstanceHandler(),
        DataclassHandler(),
        TypeHandler(),  # Handle type objects before callables
        CallableHandler(),
        CollectionHandler(),
    ]