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import inspect |
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from functools import partial |
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from typing import Optional, Callable, Tuple |
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from jsons._common_impl import get_class_name, META_ATTR |
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from jsons._main_impl import load |
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from jsons.exceptions import SignatureMismatchError, UnfulfilledArgumentError |
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def default_object_deserializer( |
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obj: dict, |
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cls: type, |
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key_transformer: Optional[Callable[[str], str]] = None, |
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strict: bool = False, |
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**kwargs) -> object: |
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""" |
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Deserialize ``obj`` into an instance of type ``cls``. If ``obj`` contains |
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keys with a certain case style (e.g. camelCase) that do not match the style |
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of ``cls`` (e.g. snake_case), a key_transformer should be used (e.g. |
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KEY_TRANSFORMER_SNAKECASE). |
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:param obj: a serialized instance of ``cls``. |
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:param cls: the type to which ``obj`` should be deserialized. |
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:param key_transformer: a function that transforms the keys in order to |
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match the attribute names of ``cls``. |
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:param strict: deserialize in strict mode. |
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:param kwargs: any keyword arguments that may be passed to the |
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deserializers. |
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:return: an instance of type ``cls``. |
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""" |
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obj, kwargs = _check_and_transform_keys(obj, key_transformer, **kwargs) |
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kwargs['strict'] = strict |
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constructor_args = _get_constructor_args(obj, cls, **kwargs) |
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remaining_attrs = _get_remaining_args(obj, cls, constructor_args, |
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strict, kwargs['fork_inst']) |
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instance = cls(**constructor_args) |
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_set_remaining_attrs(instance, remaining_attrs, **kwargs) |
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return instance |
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def _get_constructor_args(obj, cls, attr_getters=None, **kwargs) -> dict: |
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# Loop through the signature of cls: the type we try to deserialize to. For |
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# every required parameter, we try to get the corresponding value from |
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# json_obj. |
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signature_parameters = inspect.signature(cls.__init__).parameters |
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attr_getters = dict(**(attr_getters or {})) |
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value_for_attr_part = partial(_get_value_for_attr, obj=obj, cls=cls, |
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attr_getters=attr_getters, **kwargs) |
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args_gen = (value_for_attr_part(sig_key=sig_key, sig=sig) for sig_key, sig |
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in signature_parameters.items() if sig_key != 'self') |
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constructor_args_in_obj = {key: value for key, value in args_gen if key} |
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return constructor_args_in_obj |
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def _get_value_for_attr(obj, cls, sig_key, sig, attr_getters, **kwargs): |
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result = None, None |
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if obj and sig_key in obj: |
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# This argument is in obj. |
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arg_cls = None |
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if sig.annotation != inspect.Parameter.empty: |
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arg_cls = sig.annotation |
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value = load(obj[sig_key], arg_cls, **kwargs) |
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result = sig_key, value |
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elif sig_key in attr_getters: |
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# There exists an attr_getter for this argument. |
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attr_getter = attr_getters.pop(sig_key) |
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result = sig_key, attr_getter() |
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elif sig.default != inspect.Parameter.empty: |
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# There is a default value for this argument. |
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result = sig_key, sig.default |
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elif sig.kind not in (inspect.Parameter.VAR_POSITIONAL, |
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inspect.Parameter.VAR_KEYWORD): |
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# This argument is no *args or **kwargs and has no value. |
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raise UnfulfilledArgumentError( |
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'No value found for "{}"'.format(sig_key), sig_key, obj, cls) |
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return result |
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def _set_remaining_attrs(instance, |
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remaining_attrs, |
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attr_getters=None, |
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**kwargs): |
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# Set any remaining attributes on the newly created instance. |
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attr_getters = attr_getters or {} |
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for attr_name in remaining_attrs: |
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loaded_attr = load(remaining_attrs[attr_name], |
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type(remaining_attrs[attr_name]), |
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**kwargs) |
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try: |
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setattr(instance, attr_name, loaded_attr) |
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except AttributeError: |
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pass # This is raised when a @property does not have a setter. |
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for attr_name, getter in attr_getters.items(): |
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setattr(instance, attr_name, getter()) |
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def _check_and_transform_keys(obj: dict, |
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key_transformer: Optional[Callable[[str], str]], |
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**kwargs) -> Tuple[dict, dict]: |
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if key_transformer: |
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obj = {key_transformer(key): obj[key] for key in obj} |
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kwargs = { |
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**kwargs, |
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'key_transformer': key_transformer |
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} |
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return obj, kwargs |
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def _get_remaining_args(obj: dict, |
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cls: type, |
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constructor_args: dict, |
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strict: bool, |
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fork_inst: type) -> dict: |
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# Get the remaining args or raise if strict and the signature is unmatched. |
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remaining_attrs = {attr_name: obj[attr_name] for attr_name in obj |
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if attr_name not in constructor_args |
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and attr_name != META_ATTR} |
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if strict and remaining_attrs: |
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unexpected_arg = list(remaining_attrs.keys())[0] |
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err_msg = ('Type "{}" does not expect "{}"' |
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.format(get_class_name(cls, fork_inst=fork_inst), |
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unexpected_arg)) |
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raise SignatureMismatchError(err_msg, unexpected_arg, obj, cls) |
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return remaining_attrs |
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ramonhagenaars /
jsons
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