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import inspect |
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from typing import Optional, Callable, Tuple |
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from jsons._cache import cached |
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from jsons._compatibility_impl import get_type_hints |
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from jsons._load_impl import load |
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from jsons.exceptions import SignatureMismatchError, UnfulfilledArgumentError |
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from jsons._common_impl import ( |
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get_class_name, |
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META_ATTR, |
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get_cls_from_str, |
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determine_precedence, |
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can_match_with_none |
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) |
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def default_object_deserializer( |
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obj: dict, |
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cls: type, |
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*, |
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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( |
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obj, |
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cls, |
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meta_hints, |
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attr_getters=None, |
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**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 = _get_signature(cls) |
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hints = get_type_hints(cls.__init__) |
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attr_getters = dict(**(attr_getters or {})) |
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result = {} |
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for sig_key, sig in signature_parameters.items(): |
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if sig_key != 'self': |
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key, value = _get_value_for_attr(obj=obj, |
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orig_cls=cls, |
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meta_hints=meta_hints, |
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attr_getters=attr_getters, |
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sig_key=sig_key, |
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cls=hints.get(sig_key, None), |
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sig=sig, |
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**kwargs) |
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if key: |
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result[key] = value |
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return result |
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@cached |
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def _get_signature(cls): |
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return inspect.signature(cls.__init__).parameters |
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def _get_value_for_attr( |
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obj, |
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cls, |
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orig_cls, |
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sig_key, |
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sig, |
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meta_hints, |
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attr_getters, |
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**kwargs): |
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# Find a value for the attribute (with signature sig_key). |
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if obj and sig_key in obj: |
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# This argument is in obj. |
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result = sig_key, _get_value_from_obj(obj, cls, sig, sig_key, |
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meta_hints, **kwargs) |
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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 in (inspect.Parameter.VAR_POSITIONAL, |
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inspect.Parameter.VAR_KEYWORD): |
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# This argument is either *args or **kwargs. |
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result = None, None |
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elif can_match_with_none(cls): |
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# It is fine that there is no value. |
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result = sig_key, None |
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else: |
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raise UnfulfilledArgumentError( |
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'No value found for "{}"'.format(sig_key), sig_key, obj, orig_cls) |
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return result |
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def _get_value_from_obj(obj, cls, sig, sig_key, meta_hints, **kwargs): |
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# Obtain the value for the attribute with the given signature from the |
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# given obj. Try to obtain the class of this attribute from the meta info |
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# or from type hints. |
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cls_key = '/{}'.format(sig_key) |
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cls_str_from_meta = meta_hints.get(cls_key, None) |
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new_hints = meta_hints |
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cls_from_meta = None |
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if cls_str_from_meta: |
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cls_from_meta = get_cls_from_str( |
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cls_str_from_meta, obj, kwargs['fork_inst']) |
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# Rebuild the class hints: cls_key becomes the new root. |
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new_hints = { |
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key.replace(cls_key, '/'): meta_hints[key] |
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for key in meta_hints |
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if key != '/' |
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} |
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cls_ = determine_precedence(cls=cls, cls_from_meta=cls_from_meta, |
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cls_from_type=None, inferred_cls=True) |
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value = load(obj[sig_key], cls_, meta_hints=new_hints, **kwargs) |
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return value |
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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
