def _mapping_to_instance(mapping: Mapping,
destination_type: Type[T],
instantiator: Callable = None,
expand_kwargs=True) -> T:
"""Convert a dictionary-like object into an instance of the given type
This conversion is performed recursively. If the passed type
class contains child structures, then the corresponding
child keys of the dictionary will be mapped.
If `instantiator` is provided, it will be called rather than simply
calling `destination_type`.
If `expand_kwargs` is True then the the parameters will be
expended (i.e. **) when the `destination_type` / `instantiator`
is called.
"""
import lightbus.config.structure
hints = get_type_hints(destination_type, None,
lightbus.config.structure.__dict__)
parameters = {}
if mapping is None:
return None
# Iterate through each key/type-hint pairing in the destination type
for key, hint in hints.items():
value = mapping.get(key)
if key not in mapping:
# This attribute has not been provided by in the mapping. Skip it
continue
hint_type, hint_args = parse_hint(hint)
# Is this an Optional[] hint (which looks like Union[Thing, None])
if is_optional(hint) and value is not None:
# Yep, it's an Optional. So unwrap it.
hint = hint_args[0]
if issubclass_safe(hint_type,
Mapping) and hint_args and len(hint_args) == 2:
parameters[key] = dict()
for k, v in value.items():
parameters[key][k] = cast_to_hint(v, hint_args[1])
else:
parameters[key] = cast_to_hint(value, hint)
instantiator = instantiator or destination_type
if expand_kwargs:
return instantiator(**parameters)
else:
return instantiator(parameters)
def python_type_to_json_schemas(type_):
"""Convert a python type hint to its JSON schema representations
Note that a type hint may actually have several possible representations,
which is why this function returns a list of schemas. An example of this is
the `Union` type hint. These are later combined via `wrap_with_any_of()`
"""
# pylint: disable=too-many-return-statements
type_, hint_args = parse_hint(type_)
if type_ == Union:
return list(
itertools.chain(*map(python_type_to_json_schemas, hint_args)))
if type_ == empty:
return [{}]
elif type_ in (Any, ...):
return [{}]
elif hasattr(type_, "__to_bus__"):
return python_type_to_json_schemas(
inspect.signature(type_.__to_bus__).return_annotation)
elif issubclass_safe(type_, (str, bytes, complex, UUID)):
return [{"type": "string"}]
elif issubclass_safe(type_, Decimal):
return [{"type": "string", "pattern": r"^-?\d+(\.\d+)?$"}]
elif issubclass_safe(type_, (bool, )):
return [{"type": "boolean"}]
elif issubclass_safe(type_, (float, )):
return [{"type": "number"}]
elif issubclass_safe(type_, (int, )):
return [{"type": "integer"}]
elif issubclass_safe(type_,
(Mapping, )) and hint_args and hint_args[0] == str:
# Mapping with strings as keys
return [{
"type":
"object",
"additionalProperties":
wrap_with_any_of(python_type_to_json_schemas(hint_args[1])),
}]
elif issubclass_safe(type_, (dict, Mapping)):
return [{"type": "object"}]
elif issubclass_safe(type_, tuple) and hasattr(type_, "_fields"):
# Named tuple
return [make_custom_object_schema(type_, property_names=type_._fields)]
elif issubclass_safe(type_, Enum) and type_.__members__:
# Enum
enum_first_value = list(type_.__members__.values())[0].value
schema = {}
try:
schema["type"] = python_type_to_json_schemas(
type(enum_first_value))[0]["type"]
schema["enum"] = [v.value for v in type_.__members__.values()]
except KeyError:
logger.warning(
f"Could not determine type for values in enum: {type_}")
return [schema]
elif issubclass_safe(type_, (Tuple, )) and hint_args:
return [{
"type":
"array",
"maxItems":
len(hint_args),
"minItems":
len(hint_args),
"items": [
wrap_with_any_of(python_type_to_json_schemas(sub_type))
for sub_type in hint_args
],
}]
elif issubclass_safe(type_, (list, tuple, set)):
schema = {"type": "array"}
if hint_args:
schema["items"] = wrap_with_any_of(
python_type_to_json_schemas(hint_args[0]))
return [schema]
elif issubclass_safe(type_, NoneType) or type_ is None:
return [{"type": "null"}]
elif issubclass_safe(type_, (datetime.datetime)):
return [{"type": "string", "format": "date-time"}]
elif issubclass_safe(type_, (datetime.date)):
return [{"type": "string", "format": "date"}]
elif issubclass_safe(type_, (datetime.time)):
return [{"type": "string", "format": "time"}]
elif getattr(type_, "__annotations__", None):
# Custom class
return [make_custom_object_schema(type_)]
else:
logger.warning(
f"Could not convert python type to json schema type: {type_}. If it is a class, "
"ensure it's class-level variables have type hints.")
return [{}]
def cast_to_hint(value: V, hint: H) -> Union[V, H]:
"""Cast a value into a given type hint
If a value cannot be cast then the original value will be returned
and a warning emitted
"""
# pylint: disable=too-many-return-statements
if value is None:
return None
elif hint in (Any, ...):
return value
optional_hint = is_optional(hint)
if optional_hint and value is not None:
hint = optional_hint
hint_type, hint_args = parse_hint(hint)
is_class = inspect.isclass(hint_type)
if hint_type == Union:
# We don't attempt to deal with unions for now
return value
elif hint == inspect.Parameter.empty:
# Empty annotation
return value
elif isinstance_safe(value, hint):
# Already correct type
return value
elif hasattr(hint, "__from_bus__"):
# Hint supports custom deserializing.
return _mapping_to_instance(
mapping=value,
destination_type=hint,
instantiator=hint.__from_bus__,
expand_kwargs=False,
)
elif issubclass_safe(hint, bytes):
return b64decode(value.encode("utf8"))
elif type_is_namedtuple(hint) and isinstance_safe(value, Mapping):
return _mapping_to_instance(mapping=value, destination_type=hint)
elif type_is_dataclass(hint) and isinstance_safe(value, Mapping):
return _mapping_to_instance(mapping=value, destination_type=hint)
elif is_class and issubclass_safe(
hint_type, datetime.datetime) and isinstance_safe(value, str):
# Datetime as a string
return dateutil.parser.parse(value)
elif is_class and issubclass_safe(
hint_type, datetime.date) and isinstance_safe(value, str):
# Date as a string
return cast_or_warning(lambda v: dateutil.parser.parse(v).date(),
value)
elif is_class and issubclass_safe(hint_type, list):
# Lists
if hint_args and hasattr(value, "__iter__"):
value = [cast_to_hint(i, hint_args[0]) for i in value]
return cast_or_warning(list, value)
elif is_class and issubclass_safe(hint_type, tuple):
# Tuples
if hint_args and hasattr(value, "__iter__"):
value = [
cast_to_hint(h, hint_args[i]) for i, h in enumerate(value)
]
return cast_or_warning(tuple, value)
elif is_class and issubclass_safe(hint_type, set):
# Sets
if hint_args and hasattr(value, "__iter__"):
value = [cast_to_hint(i, hint_args[0]) for i in value]
return cast_or_warning(set, value)
elif (inspect.isclass(hint) and hasattr(hint, "__annotations__")
and not issubclass_safe(hint_type, Enum)):
logger.warning(
f"Cannot cast to arbitrary class {hint}, using un-casted value. "
f"If you want to receive custom objects you can 1) "
f"use a NamedTuple, 2) use a dataclass, or 3) specify the "
f"__from_bus__() and __to_bus__() magic methods.")
return value
else:
return cast_or_warning(hint, value)
