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|
| """Improved JSON serialization. |
| """ |
|
|
| import builtins |
| import json |
| import numbers |
| import operator |
|
|
|
|
| JsonDecoder = json.JSONDecoder |
|
|
|
|
| class JsonEncoder(json.JSONEncoder): |
| """Customizable JSON encoder. |
| |
| If the object implements __getstate__, then that method is invoked, and its |
| result is serialized instead of the object itself. |
| """ |
|
|
| def default(self, value): |
| try: |
| get_state = value.__getstate__ |
| except AttributeError: |
| pass |
| else: |
| return get_state() |
| return super().default(value) |
|
|
|
|
| class JsonObject(object): |
| """A wrapped Python object that formats itself as JSON when asked for a string |
| representation via str() or format(). |
| """ |
|
|
| json_encoder_factory = JsonEncoder |
| """Used by __format__ when format_spec is not empty.""" |
|
|
| json_encoder = json_encoder_factory(indent=4) |
| """The default encoder used by __format__ when format_spec is empty.""" |
|
|
| def __init__(self, value): |
| assert not isinstance(value, JsonObject) |
| self.value = value |
|
|
| def __getstate__(self): |
| raise NotImplementedError |
|
|
| def __repr__(self): |
| return builtins.repr(self.value) |
|
|
| def __str__(self): |
| return format(self) |
|
|
| def __format__(self, format_spec): |
| """If format_spec is empty, uses self.json_encoder to serialize self.value |
| as a string. Otherwise, format_spec is treated as an argument list to be |
| passed to self.json_encoder_factory - which defaults to JSONEncoder - and |
| then the resulting formatter is used to serialize self.value as a string. |
| |
| Example:: |
| |
| format("{0} {0:indent=4,sort_keys=True}", json.repr(x)) |
| """ |
| if format_spec: |
| |
| |
| |
| |
| |
| |
| |
| make_encoder = "json_encoder_factory(" + format_spec + ")" |
| encoder = eval( |
| make_encoder, {"json_encoder_factory": self.json_encoder_factory} |
| ) |
| else: |
| encoder = self.json_encoder |
| return encoder.encode(self.value) |
|
|
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| |
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| |
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|
|
|
| def _converter(value, classinfo): |
| """Convert value (str) to number, otherwise return None if is not possible""" |
| for one_info in classinfo: |
| if issubclass(one_info, numbers.Number): |
| try: |
| return one_info(value) |
| except ValueError: |
| pass |
|
|
|
|
| def of_type(*classinfo, **kwargs): |
| """Returns a validator for a JSON property that requires it to have a value of |
| the specified type. If optional=True, () is also allowed. |
| |
| The meaning of classinfo is the same as for isinstance(). |
| """ |
|
|
| assert len(classinfo) |
| optional = kwargs.pop("optional", False) |
| assert not len(kwargs) |
|
|
| def validate(value): |
| if (optional and value == ()) or isinstance(value, classinfo): |
| return value |
| else: |
| converted_value = _converter(value, classinfo) |
| if converted_value: |
| return converted_value |
|
|
| if not optional and value == (): |
| raise ValueError("must be specified") |
| raise TypeError("must be " + " or ".join(t.__name__ for t in classinfo)) |
|
|
| return validate |
|
|
|
|
| def default(default): |
| """Returns a validator for a JSON property with a default value. |
| |
| The validator will only allow property values that have the same type as the |
| specified default value. |
| """ |
|
|
| def validate(value): |
| if value == (): |
| return default |
| elif isinstance(value, type(default)): |
| return value |
| else: |
| raise TypeError("must be {0}".format(type(default).__name__)) |
|
|
| return validate |
|
|
|
|
| def enum(*values, **kwargs): |
| """Returns a validator for a JSON enum. |
| |
| The validator will only allow the property to have one of the specified values. |
| |
| If optional=True, and the property is missing, the first value specified is used |
| as the default. |
| """ |
|
|
| assert len(values) |
| optional = kwargs.pop("optional", False) |
| assert not len(kwargs) |
|
|
| def validate(value): |
| if optional and value == (): |
| return values[0] |
| elif value in values: |
| return value |
| else: |
| raise ValueError("must be one of: {0!r}".format(list(values))) |
|
|
| return validate |
|
|
|
|
| def array(validate_item=False, vectorize=False, size=None): |
| """Returns a validator for a JSON array. |
| |
| If the property is missing, it is treated as if it were []. Otherwise, it must |
| be a list. |
| |
| If validate_item=False, it's treated as if it were (lambda x: x) - i.e. any item |
| is considered valid, and is unchanged. If validate_item is a type or a tuple, |
| it's treated as if it were json.of_type(validate). |
| |
| Every item in the list is replaced with validate_item(item) in-place, propagating |
| any exceptions raised by the latter. If validate_item is a type or a tuple, it is |
| treated as if it were json.of_type(validate_item). |
| |
| If vectorize=True, and the value is neither a list nor a dict, it is treated as |
| if it were a single-element list containing that single value - e.g. "foo" is |
| then the same as ["foo"]; but {} is an error, and not [{}]. |
| |
| If size is not None, it can be an int, a tuple of one int, a tuple of two ints, |
| or a set. If it's an int, the array must have exactly that many elements. If it's |
| a tuple of one int, it's the minimum length. If it's a tuple of two ints, they |
| are the minimum and the maximum lengths. If it's a set, it's the set of sizes that |
| are valid - e.g. for {2, 4}, the array can be either 2 or 4 elements long. |
| """ |
|
|
| if not validate_item: |
| validate_item = lambda x: x |
| elif isinstance(validate_item, type) or isinstance(validate_item, tuple): |
| validate_item = of_type(validate_item) |
|
|
| if size is None: |
| validate_size = lambda _: True |
| elif isinstance(size, set): |
| size = {operator.index(n) for n in size} |
| validate_size = lambda value: ( |
| len(value) in size |
| or "must have {0} elements".format( |
| " or ".join(str(n) for n in sorted(size)) |
| ) |
| ) |
| elif isinstance(size, tuple): |
| assert 1 <= len(size) <= 2 |
| size = tuple(operator.index(n) for n in size) |
| min_len, max_len = (size + (None,))[0:2] |
| validate_size = lambda value: ( |
| "must have at least {0} elements".format(min_len) |
| if len(value) < min_len |
| else "must have at most {0} elements".format(max_len) |
| if max_len is not None and len(value) < max_len |
| else True |
| ) |
| else: |
| size = operator.index(size) |
| validate_size = lambda value: ( |
| len(value) == size or "must have {0} elements".format(size) |
| ) |
|
|
| def validate(value): |
| if value == (): |
| value = [] |
| elif vectorize and not isinstance(value, (list, dict)): |
| value = [value] |
|
|
| of_type(list)(value) |
|
|
| size_err = validate_size(value) |
| if size_err is not True: |
| raise ValueError(size_err) |
|
|
| for i, item in enumerate(value): |
| try: |
| value[i] = validate_item(item) |
| except (TypeError, ValueError) as exc: |
| raise type(exc)(f"[{repr(i)}] {exc}") |
| return value |
|
|
| return validate |
|
|
|
|
| def object(validate_value=False): |
| """Returns a validator for a JSON object. |
| |
| If the property is missing, it is treated as if it were {}. Otherwise, it must |
| be a dict. |
| |
| If validate_value=False, it's treated as if it were (lambda x: x) - i.e. any |
| value is considered valid, and is unchanged. If validate_value is a type or a |
| tuple, it's treated as if it were json.of_type(validate_value). |
| |
| Every value in the dict is replaced with validate_value(value) in-place, propagating |
| any exceptions raised by the latter. If validate_value is a type or a tuple, it is |
| treated as if it were json.of_type(validate_value). Keys are not affected. |
| """ |
|
|
| if isinstance(validate_value, type) or isinstance(validate_value, tuple): |
| validate_value = of_type(validate_value) |
|
|
| def validate(value): |
| if value == (): |
| return {} |
|
|
| of_type(dict)(value) |
| if validate_value: |
| for k, v in value.items(): |
| try: |
| value[k] = validate_value(v) |
| except (TypeError, ValueError) as exc: |
| raise type(exc)(f"[{repr(k)}] {exc}") |
| return value |
|
|
| return validate |
|
|
|
|
| def repr(value): |
| return JsonObject(value) |
|
|
|
|
| dumps = json.dumps |
| loads = json.loads |
|
|