jsons.deserializers.default_object._get_value_for_attr() - Code Metrics - Inspection of "Release/0.9.0" - ramonhagenaars/jsons - Measure and Improve Code Quality continuously with Scrutinizer

Passed

Pull Request — master (#65)

by Ramon

created 2019-07-14 11:48 UTC

_get_value_for_attr() B

↳ Parent: jsons.deserializers.default_object

Complexity

Conditions

Size

Total Lines	32
Code Lines	25

Duplication

Lines	0
Ratio	0 %

Importance

Changes

Metric	Value
eloc	25
dl	0
loc	32
rs	7.8799
c	0
b	0
f	0
cc	7
nop	8

How to fix Many Parameters

import inspect
from typing import Optional, Callable, Tuple
from jsons._cache import cached
from jsons._compatibility_impl import get_type_hints
from jsons._load_impl import load
from jsons.exceptions import SignatureMismatchError, UnfulfilledArgumentError
from jsons._common_impl import (
    get_class_name,
    META_ATTR,
    get_cls_from_str,
    determine_precedence,
    can_match_with_none
)


def default_object_deserializer(
        obj: dict,
        cls: type,
        *,
        key_transformer: Optional[Callable[[str], str]] = None,
        strict: bool = False,
        **kwargs) -> object:
    """
    Deserialize ``obj`` into an instance of type ``cls``. If ``obj`` contains
    keys with a certain case style (e.g. camelCase) that do not match the style
    of ``cls`` (e.g. snake_case), a key_transformer should be used (e.g.
    KEY_TRANSFORMER_SNAKECASE).
    :param obj: a serialized instance of ``cls``.
    :param cls: the type to which ``obj`` should be deserialized.
    :param key_transformer: a function that transforms the keys in order to
    match the attribute names of ``cls``.
    :param strict: deserialize in strict mode.
    :param kwargs: any keyword arguments that may be passed to the
    deserializers.
    :return: an instance of type ``cls``.
    """
    obj, kwargs = _check_and_transform_keys(obj, key_transformer, **kwargs)
    kwargs['strict'] = strict
    constructor_args = _get_constructor_args(obj, cls, **kwargs)
    remaining_attrs = _get_remaining_args(obj, cls, constructor_args,
                                          strict, kwargs['fork_inst'])
    instance = cls(**constructor_args)
    _set_remaining_attrs(instance, remaining_attrs, **kwargs)
    return instance


def _get_constructor_args(
        obj,
        cls,
        meta_hints,
        attr_getters=None,
        **kwargs) -> dict:
    # Loop through the signature of cls: the type we try to deserialize to. For
    # every required parameter, we try to get the corresponding value from
    # json_obj.
    signature_parameters = _get_signature(cls)
    hints = get_type_hints(cls.__init__)
    attr_getters = dict(**(attr_getters or {}))

    result = {}
    for sig_key, sig in signature_parameters.items():
        if sig_key != 'self':
            key, value = _get_value_for_attr(obj=obj,
                                             orig_cls=cls,
                                             meta_hints=meta_hints,
                                             attr_getters=attr_getters,
                                             sig_key=sig_key,
                                             cls=hints.get(sig_key, None),
                                             sig=sig,
                                             **kwargs)
            if key:
                result[key] = value
    return result


@cached
def _get_signature(cls):
    return inspect.signature(cls.__init__).parameters


def _get_value_for_attr(
        obj,
        cls,
        orig_cls,
        sig_key,
        sig,
        meta_hints,
        attr_getters,
        **kwargs):
    # Find a value for the attribute (with signature sig_key).
    if obj and sig_key in obj:
        # This argument is in obj.
        result = sig_key, _get_value_from_obj(obj, cls, sig, sig_key,
                                              meta_hints, **kwargs)
    elif sig_key in attr_getters:
        # There exists an attr_getter for this argument.
        attr_getter = attr_getters.pop(sig_key)
        result = sig_key, attr_getter()
    elif sig.default != inspect.Parameter.empty:
        # There is a default value for this argument.
        result = sig_key, sig.default
    elif sig.kind in (inspect.Parameter.VAR_POSITIONAL,
                      inspect.Parameter.VAR_KEYWORD):
        # This argument is either *args or **kwargs.
        result = None, None
    elif can_match_with_none(cls):
        # It is fine that there is no value.
        result = sig_key, None
    else:
        raise UnfulfilledArgumentError(
            'No value found for "{}"'.format(sig_key), sig_key, obj, orig_cls)
    return result


def _get_value_from_obj(obj, cls, sig, sig_key, meta_hints, **kwargs):
    # Obtain the value for the attribute with the given signature from the
    # given obj. Try to obtain the class of this attribute from the meta info
    # or from type hints.
    cls_key = '/{}'.format(sig_key)
    cls_str_from_meta = meta_hints.get(cls_key, None)
    new_hints = meta_hints
    cls_from_meta = None
    if cls_str_from_meta:
        cls_from_meta = get_cls_from_str(
            cls_str_from_meta, obj, kwargs['fork_inst'])
        # Rebuild the class hints: cls_key becomes the new root.
        new_hints = {
            key.replace(cls_key, '/'): meta_hints[key]
            for key in meta_hints
            if key != '/'
        }
    cls_ = determine_precedence(cls=cls, cls_from_meta=cls_from_meta,
                                cls_from_type=None, inferred_cls=True)
    value = load(obj[sig_key], cls_, meta_hints=new_hints, **kwargs)
    return value


def _set_remaining_attrs(instance,
                         remaining_attrs,
                         attr_getters=None,
                         **kwargs):
    # Set any remaining attributes on the newly created instance.
    attr_getters = attr_getters or {}
    for attr_name in remaining_attrs:
        loaded_attr = load(remaining_attrs[attr_name],
                           type(remaining_attrs[attr_name]),
                           **kwargs)
        try:
            setattr(instance, attr_name, loaded_attr)
        except AttributeError:
            pass  # This is raised when a @property does not have a setter.
    for attr_name, getter in attr_getters.items():
        setattr(instance, attr_name, getter())


def _check_and_transform_keys(obj: dict,
                              key_transformer: Optional[Callable[[str], str]],
                              **kwargs) -> Tuple[dict, dict]:
    if key_transformer:
        obj = {key_transformer(key): obj[key] for key in obj}
        kwargs = {
            **kwargs,
            'key_transformer': key_transformer
        }
    return obj, kwargs


def _get_remaining_args(obj: dict,
                        cls: type,
                        constructor_args: dict,
                        strict: bool,
                        fork_inst: type) -> dict:
    # Get the remaining args or raise if strict and the signature is unmatched.
    remaining_attrs = {attr_name: obj[attr_name] for attr_name in obj
                       if attr_name not in constructor_args
                       and attr_name != META_ATTR}
    if strict and remaining_attrs:
        unexpected_arg = list(remaining_attrs.keys())[0]
        err_msg = ('Type "{}" does not expect "{}"'
                   .format(get_class_name(cls, fork_inst=fork_inst),
                           unexpected_arg))
        raise SignatureMismatchError(err_msg, unexpected_arg, obj, cls)
    return remaining_attrs


1			import inspect
2			from typing import Optional, Callable, Tuple
3			from jsons._cache import cached
4			from jsons._compatibility_impl import get_type_hints
5			from jsons._load_impl import load
6			from jsons.exceptions import SignatureMismatchError, UnfulfilledArgumentError
7			from jsons._common_impl import (
8			get_class_name,
9			META_ATTR,
10			get_cls_from_str,
11			determine_precedence,
12			can_match_with_none
13			)
14
15
16			def default_object_deserializer(
17			obj: dict,
18			cls: type,
19			*,
20			key_transformer: Optional[Callable[[str], str]] = None,
21			strict: bool = False,
22			**kwargs) -> object:
23			"""
24			Deserialize ``obj`` into an instance of type ``cls``. If ``obj`` contains
25			keys with a certain case style (e.g. camelCase) that do not match the style
26			of ``cls`` (e.g. snake_case), a key_transformer should be used (e.g.
27			KEY_TRANSFORMER_SNAKECASE).
28			:param obj: a serialized instance of ``cls``.
29			:param cls: the type to which ``obj`` should be deserialized.
30			:param key_transformer: a function that transforms the keys in order to
31			match the attribute names of ``cls``.
32			:param strict: deserialize in strict mode.
33			:param kwargs: any keyword arguments that may be passed to the
34			deserializers.
35			:return: an instance of type ``cls``.
36			"""
37			obj, kwargs = _check_and_transform_keys(obj, key_transformer, **kwargs)
38			kwargs['strict'] = strict
39			constructor_args = _get_constructor_args(obj, cls, **kwargs)
40			remaining_attrs = _get_remaining_args(obj, cls, constructor_args,
41			strict, kwargs['fork_inst'])
42			instance = cls(**constructor_args)
43			_set_remaining_attrs(instance, remaining_attrs, **kwargs)
44			return instance
45
46
47			def _get_constructor_args(
48			obj,
49			cls,
50			meta_hints,
51			attr_getters=None,
52			**kwargs) -> dict:
53			# Loop through the signature of cls: the type we try to deserialize to. For
54			# every required parameter, we try to get the corresponding value from
55			# json_obj.
56			signature_parameters = _get_signature(cls)
57			hints = get_type_hints(cls.__init__)
58			attr_getters = dict(**(attr_getters or {}))
59
60			result = {}
61			for sig_key, sig in signature_parameters.items():
62			if sig_key != 'self':
63			key, value = _get_value_for_attr(obj=obj,
64			orig_cls=cls,
65			meta_hints=meta_hints,
66			attr_getters=attr_getters,
67			sig_key=sig_key,
68			cls=hints.get(sig_key, None),
69			sig=sig,
70			**kwargs)
71			if key:
72			result[key] = value
73			return result
74
75
76			@cached
77			def _get_signature(cls):
78			return inspect.signature(cls.__init__).parameters
79
80
81			def _get_value_for_attr(
82			obj,
83			cls,
84			orig_cls,
85			sig_key,
86			sig,
87			meta_hints,
88			attr_getters,
89			**kwargs):
90			# Find a value for the attribute (with signature sig_key).
91			if obj and sig_key in obj:
92			# This argument is in obj.
93			result = sig_key, _get_value_from_obj(obj, cls, sig, sig_key,
94			meta_hints, **kwargs)
95			elif sig_key in attr_getters:
96			# There exists an attr_getter for this argument.
97			attr_getter = attr_getters.pop(sig_key)
98			result = sig_key, attr_getter()
99			elif sig.default != inspect.Parameter.empty:
100			# There is a default value for this argument.
101			result = sig_key, sig.default
102			elif sig.kind in (inspect.Parameter.VAR_POSITIONAL,
103			inspect.Parameter.VAR_KEYWORD):
104			# This argument is either args or *kwargs.
105			result = None, None
106			elif can_match_with_none(cls):
107			# It is fine that there is no value.
108			result = sig_key, None
109			else:
110			raise UnfulfilledArgumentError(
111			'No value found for "{}"'.format(sig_key), sig_key, obj, orig_cls)
112			return result
113
114
115			def _get_value_from_obj(obj, cls, sig, sig_key, meta_hints, **kwargs):
116			# Obtain the value for the attribute with the given signature from the
117			# given obj. Try to obtain the class of this attribute from the meta info
118			# or from type hints.
119			cls_key = '/{}'.format(sig_key)
120			cls_str_from_meta = meta_hints.get(cls_key, None)
121			new_hints = meta_hints
122			cls_from_meta = None
123			if cls_str_from_meta:
124			cls_from_meta = get_cls_from_str(
125			cls_str_from_meta, obj, kwargs['fork_inst'])
126			# Rebuild the class hints: cls_key becomes the new root.
127			new_hints = {
128			key.replace(cls_key, '/'): meta_hints[key]
129			for key in meta_hints
130			if key != '/'
131			}
132			cls_ = determine_precedence(cls=cls, cls_from_meta=cls_from_meta,
133			cls_from_type=None, inferred_cls=True)
134			value = load(obj[sig_key], cls_, meta_hints=new_hints, **kwargs)
135			return value
136
137
138			def _set_remaining_attrs(instance,
139			remaining_attrs,
140			attr_getters=None,
141			**kwargs):
142			# Set any remaining attributes on the newly created instance.
143			attr_getters = attr_getters or {}
144			for attr_name in remaining_attrs:
145			loaded_attr = load(remaining_attrs[attr_name],
146			type(remaining_attrs[attr_name]),
147			**kwargs)
148			try:
149			setattr(instance, attr_name, loaded_attr)
150			except AttributeError:
151			pass # This is raised when a @property does not have a setter.
152			for attr_name, getter in attr_getters.items():
153			setattr(instance, attr_name, getter())
154
155
156			def _check_and_transform_keys(obj: dict,
157			key_transformer: Optional[Callable[[str], str]],
158			**kwargs) -> Tuple[dict, dict]:
159			if key_transformer:
160			obj = {key_transformer(key): obj[key] for key in obj}
161			kwargs = {
162			**kwargs,
163			'key_transformer': key_transformer
164			}
165			return obj, kwargs
166
167
168			def _get_remaining_args(obj: dict,
169			cls: type,
170			constructor_args: dict,
171			strict: bool,
172			fork_inst: type) -> dict:
173			# Get the remaining args or raise if strict and the signature is unmatched.
174			remaining_attrs = {attr_name: obj[attr_name] for attr_name in obj
175			if attr_name not in constructor_args
176			and attr_name != META_ATTR}
177			if strict and remaining_attrs:
178			unexpected_arg = list(remaining_attrs.keys())[0]
179			err_msg = ('Type "{}" does not expect "{}"'
180			.format(get_class_name(cls, fork_inst=fork_inst),
181			unexpected_arg))
182			raise SignatureMismatchError(err_msg, unexpected_arg, obj, cls)
183			return remaining_attrs
184

ramonhagenaars / jsons

Pull Request — master (#65)

_get_value_for_attr() B

Complexity

Size

Duplication

Importance

How to fix Many Parameters

Many Parameters

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