webargs.core — webargs 6.1.0 documentation
Description: Declarative parsing and validation of HTTP request objects.

# Source code for webargs.core

    import functools
    import inspect
    import typing
    import logging
    import warnings
    from collections.abc import Mapping
    import json

    import marshmallow as ma
    from marshmallow import ValidationError
    from marshmallow.utils import missing

    from webargs.compat import MARSHMALLOW_VERSION_INFO
    from webargs.dict2schema import dict2schema
    from webargs.fields import DelimitedList

    logger = logging.getLogger(__name__)

    __all__ = [
        "ValidationError",
        "dict2schema",
        "is_multiple",
        "Parser",
        "missing",
        "parse_json",
    ]

    DEFAULT_VALIDATION_STATUS = 422  # type: int

    def _callable_or_raise(obj):
        """Makes sure an object is callable if it is not ``None``. If not
        callable, a ValueError is raised.
        """
        if obj and not callable(obj):
            raise ValueError("{!r} is not callable.".format(obj))
        return obj

    def is_multiple(field):
        """Return whether or not `field` handles repeated/multi-value arguments."""
        return isinstance(field, ma.fields.List) and not isinstance(field, DelimitedList)

    def get_mimetype(content_type):
        return content_type.split(";")[0].strip() if content_type else None

    # Adapted from werkzeug:
    # https://github.com/mitsuhiko/werkzeug/blob/master/werkzeug/wrappers.py
    def is_json(mimetype):
        """Indicates if this mimetype is JSON or not.  By default a request
        is considered to include JSON data if the mimetype is
        ``application/json`` or ``application/*+json``.
        """
        if not mimetype:
            return False
        if ";" in mimetype:  # Allow Content-Type header to be passed
            mimetype = get_mimetype(mimetype)
        if mimetype == "application/json":
            return True
        if mimetype.startswith("application/") and mimetype.endswith("+json"):
            return True
        return False

    def parse_json(string, *, encoding="utf-8"):
        if isinstance(string, bytes):
            try:
                string = string.decode(encoding)
            except UnicodeDecodeError as exc:
                raise json.JSONDecodeError(
                    "Bytes decoding error : {}".format(exc.reason),
                    doc=str(exc.object),
                    pos=exc.start,
                )
        return json.loads(string)

    def _ensure_list_of_callables(obj):
        if obj:
            if isinstance(obj, (list, tuple)):
                validators = obj
            elif callable(obj):
                validators = [obj]
            else:
                raise ValueError("{!r} is not a callable or list of callables.".format(obj))
        else:
            validators = []
        return validators

    class Parser:
        """Base parser class that provides high-level implementation for parsing
        a request.

        Descendant classes must provide lower-level implementations for reading
        data from  different locations, e.g. ``load_json``, ``load_querystring``,
        etc.

        :param str location: Default location to use for data
        :param callable error_handler: Custom error handler function.
        """

        #: Default location to check for data
        DEFAULT_LOCATION = "json"
        #: The marshmallow Schema class to use when creating new schemas
        DEFAULT_SCHEMA_CLASS = ma.Schema
        #: Default status code to return for validation errors
        DEFAULT_VALIDATION_STATUS = DEFAULT_VALIDATION_STATUS
        #: Default error message for validation errors
        DEFAULT_VALIDATION_MESSAGE = "Invalid value."

        #: Maps location => method name
        __location_map__ = {
            "json": "load_json",
            "querystring": "load_querystring",
            "query": "load_querystring",
            "form": "load_form",
            "headers": "load_headers",
            "cookies": "load_cookies",
            "files": "load_files",
            "json_or_form": "load_json_or_form",
        }

        def __init__(self, location=None, *, error_handler=None, schema_class=None):
            self.location = location or self.DEFAULT_LOCATION
            self.error_callback = _callable_or_raise(error_handler)
            self.schema_class = schema_class or self.DEFAULT_SCHEMA_CLASS

        def _get_loader(self, location):
            """Get the loader function for the given location.

            :raises: ValueError if a given location is invalid.
            """
            valid_locations = set(self.__location_map__.keys())
            if location not in valid_locations:
                msg = "Invalid location argument: {}".format(location)
                raise ValueError(msg)

            # Parsing function to call
            # May be a method name (str) or a function
            func = self.__location_map__.get(location)
            if func:
                if inspect.isfunction(func):
                    function = func
                else:
                    function = getattr(self, func)
            else:
                raise ValueError('Invalid location: "{}"'.format(location))
            return function

        def _load_location_data(self, *, schema, req, location):
            """Return a dictionary-like object for the location on the given request.

            Needs to have the schema in hand in order to correctly handle loading
            lists from multidict objects and `many=True` schemas.
            """
            loader_func = self._get_loader(location)
            data = loader_func(req, schema)
            # when the desired location is empty (no data), provide an empty
            # dict as the default so that optional arguments in a location
            # (e.g. optional JSON body) work smoothly
            if data is missing:
                data = {}
            return data

        def _on_validation_error(
            self, error, req, schema, location, *, error_status_code, error_headers
        ):
            # rewrite messages to be namespaced under the location which created
            # them
            # e.g. {"json":{"foo":["Not a valid integer."]}}
            #      instead of
            #      {"foo":["Not a valid integer."]}
            error.messages = {location: error.messages}
            error_handler = self.error_callback or self.handle_error
            error_handler(
                error,
                req,
                schema,
                error_status_code=error_status_code,
                error_headers=error_headers,
            )

        def _validate_arguments(self, data, validators):
            for validator in validators:
                if validator(data) is False:
                    msg = self.DEFAULT_VALIDATION_MESSAGE
                    raise ValidationError(msg, data=data)

        def _get_schema(self, argmap, req):
            """Return a `marshmallow.Schema` for the given argmap and request.

            :param argmap: Either a `marshmallow.Schema`, `dict`
                of argname -> `marshmallow.fields.Field` pairs, or a callable that returns
                a `marshmallow.Schema` instance.
            :param req: The request object being parsed.
            :rtype: marshmallow.Schema
            """
            if isinstance(argmap, ma.Schema):
                schema = argmap
            elif isinstance(argmap, type) and issubclass(argmap, ma.Schema):
                schema = argmap()
            elif callable(argmap):
                schema = argmap(req)
            else:
                schema = dict2schema(argmap, schema_class=self.schema_class)()
            if MARSHMALLOW_VERSION_INFO[0] < 3 and not schema.strict:
                warnings.warn(
                    "It is highly recommended that you set strict=True on your schema "
                    "so that the parser's error handler will be invoked when expected.",
                    UserWarning,
                )
            return schema

        def parse(
            self,
            argmap,
            req=None,
            *,
            location=None,
            validate=None,
            error_status_code=None,
            error_headers=None
        ):
            """Main request parsing method.

            :param argmap: Either a `marshmallow.Schema`, a `dict`
                of argname -> `marshmallow.fields.Field` pairs, or a callable
                which accepts a request and returns a `marshmallow.Schema`.
            :param req: The request object to parse.
            :param str location: Where on the request to load values.
                Can be any of the values in :py:attr:`~__location_map__`. By
                default, that means one of ``('json', 'query', 'querystring',
                'form', 'headers', 'cookies', 'files', 'json_or_form')``.
            :param callable validate: Validation function or list of validation functions
                that receives the dictionary of parsed arguments. Validator either returns a
                boolean or raises a :exc:`ValidationError`.
            :param int error_status_code: Status code passed to error handler functions when
                a `ValidationError` is raised.
            :param dict error_headers: Headers passed to error handler functions when a
                a `ValidationError` is raised.

             :return: A dictionary of parsed arguments
            """
            req = req if req is not None else self.get_default_request()
            location = location or self.location
            if req is None:
                raise ValueError("Must pass req object")
            data = None
            validators = _ensure_list_of_callables(validate)
            schema = self._get_schema(argmap, req)
            try:
                location_data = self._load_location_data(
                    schema=schema, req=req, location=location
                )
                result = schema.load(location_data)
                data = result.data if MARSHMALLOW_VERSION_INFO[0] < 3 else result
                self._validate_arguments(data, validators)
            except ma.exceptions.ValidationError as error:
                self._on_validation_error(
                    error,
                    req,
                    schema,
                    location,
                    error_status_code=error_status_code,
                    error_headers=error_headers,
                )
            return data

        def get_default_request(self):
            """Optional override. Provides a hook for frameworks that use thread-local
            request objects.
            """
            return None

        def get_request_from_view_args(self, view, args, kwargs):
            """Optional override. Returns the request object to be parsed, given a view
            function's args and kwargs.

            Used by the `use_args` and `use_kwargs` to get a request object from a
            view's arguments.

            :param callable view: The view function or method being decorated by
                `use_args` or `use_kwargs`
            :param tuple args: Positional arguments passed to ``view``.
            :param dict kwargs: Keyword arguments passed to ``view``.
            """
            return None

        @staticmethod
        def _update_args_kwargs(args, kwargs, parsed_args, as_kwargs):
            """Update args or kwargs with parsed_args depending on as_kwargs"""
            if as_kwargs:
                kwargs.update(parsed_args)
            else:
                # Add parsed_args after other positional arguments
                args += (parsed_args,)
            return args, kwargs

        def use_args(
            self,
            argmap,
            req=None,
            *,
            location=None,
            as_kwargs=False,
            validate=None,
            error_status_code=None,
            error_headers=None
        ):
            """Decorator that injects parsed arguments into a view function or method.

            Example usage with Flask: ::

                @app.route('/echo', methods=['get', 'post'])
                @parser.use_args({'name': fields.Str()}, location="querystring")
                def greet(args):
                    return 'Hello ' + args['name']

            :param argmap: Either a `marshmallow.Schema`, a `dict`
                of argname -> `marshmallow.fields.Field` pairs, or a callable
                which accepts a request and returns a `marshmallow.Schema`.
            :param str location: Where on the request to load values.
            :param bool as_kwargs: Whether to insert arguments as keyword arguments.
            :param callable validate: Validation function that receives the dictionary
                of parsed arguments. If the function returns ``False``, the parser
                will raise a :exc:`ValidationError`.
            :param int error_status_code: Status code passed to error handler functions when
                a `ValidationError` is raised.
            :param dict error_headers: Headers passed to error handler functions when a
                a `ValidationError` is raised.
            """
            location = location or self.location
            request_obj = req
            # Optimization: If argmap is passed as a dictionary, we only need
            # to generate a Schema once
            if isinstance(argmap, Mapping):
                argmap = dict2schema(argmap, schema_class=self.schema_class)()

            def decorator(func):
                req_ = request_obj

                @functools.wraps(func)
                def wrapper(*args, **kwargs):
                    req_obj = req_

                    if not req_obj:
                        req_obj = self.get_request_from_view_args(func, args, kwargs)

                    # NOTE: At this point, argmap may be a Schema, or a callable
                    parsed_args = self.parse(
                        argmap,
                        req=req_obj,
                        location=location,
                        validate=validate,
                        error_status_code=error_status_code,
                        error_headers=error_headers,
                    )
                    args, kwargs = self._update_args_kwargs(
                        args, kwargs, parsed_args, as_kwargs
                    )
                    return func(*args, **kwargs)

                wrapper.__wrapped__ = func
                return wrapper

            return decorator

        def use_kwargs(self, *args, **kwargs) -> typing.Callable:
            """Decorator that injects parsed arguments into a view function or method
            as keyword arguments.

            This is a shortcut to :meth:`use_args` with ``as_kwargs=True``.

            Example usage with Flask: ::

                @app.route('/echo', methods=['get', 'post'])
                @parser.use_kwargs({'name': fields.Str()})
                def greet(name):
                    return 'Hello ' + name

            Receives the same ``args`` and ``kwargs`` as :meth:`use_args`.
            """
            kwargs["as_kwargs"] = True
            return self.use_args(*args, **kwargs)

        def location_loader(self, name):
            """Decorator that registers a function for loading a request location.
            The wrapped function receives a schema and a request.

            The schema will usually not be relevant, but it's important in some
            cases -- most notably in order to correctly load multidict values into
            list fields. Without the schema, there would be no way to know whether
            to simply `.get()` or `.getall()` from a multidict for a given value.

            Example: ::

                from webargs import core
                parser = core.Parser()

                @parser.location_loader("name")
                def load_data(request, schema):
                    return request.data

            :param str name: The name of the location to register.
            """

            def decorator(func):
                self.__location_map__[name] = func
                return func

            return decorator

        def error_handler(self, func):
            """Decorator that registers a custom error handling function. The
            function should receive the raised error, request object,
            `marshmallow.Schema` instance used to parse the request, error status code,
            and headers to use for the error response. Overrides
            the parser's ``handle_error`` method.

            Example: ::

                from webargs import flaskparser

                parser = flaskparser.FlaskParser()

                class CustomError(Exception):
                    pass

                @parser.error_handler
                def handle_error(error, req, schema, *, status_code, headers):
                    raise CustomError(error.messages)

            :param callable func: The error callback to register.
            """
            self.error_callback = func
            return func

        def _handle_invalid_json_error(self, error, req, *args, **kwargs):
            """Internal hook for overriding treatment of JSONDecodeErrors.

            Invoked by default `load_json` implementation.

            External parsers can just implement their own behavior for load_json ,
            so this is not part of the public parser API.
            """
            raise error

        def load_json(self, req, schema):
            """Load JSON from a request object or return `missing` if no value can
            be found.
            """
            # NOTE: although this implementation is real/concrete and used by
            # several of the parsers in webargs, it relies on the internal hooks
            # `_handle_invalid_json_error` and `_raw_load_json`
            # these methods are not part of the public API and are used to simplify
            # code sharing amongst the built-in webargs parsers
            try:
                return self._raw_load_json(req)
            except json.JSONDecodeError as exc:
                if exc.doc == "":
                    return missing
                return self._handle_invalid_json_error(exc, req)
            except UnicodeDecodeError as exc:
                return self._handle_invalid_json_error(exc, req)

        def load_json_or_form(self, req, schema):
            """Load data from a request, accepting either JSON or form-encoded
            data.

            The data will first be loaded as JSON, and, if that fails, it will be
            loaded as a form post.
            """
            data = self.load_json(req, schema)
            if data is not missing:
                return data
            return self.load_form(req, schema)

        # Abstract Methods

        def _raw_load_json(self, req):
            """Internal hook method for implementing load_json()

            Get a request body for feeding in to `load_json`, and parse it either
            using core.parse_json() or similar utilities which raise
            JSONDecodeErrors.
            Ensure consistent behavior when encountering decoding errors.

            The default implementation here simply returns `missing`, and the default
            implementation of `load_json` above will pass that value through.
            However, by implementing a "mostly concrete" version of load_json with
            this as a hook for getting data, we consolidate the logic for handling
            those JSONDecodeErrors.
            """
            return missing

        def load_querystring(self, req, schema):
            """Load the query string of a request object or return `missing` if no
            value can be found.
            """
            return missing

        def load_form(self, req, schema):
            """Load the form data of a request object or return `missing` if no
            value can be found.
            """
            return missing

        def load_headers(self, req, schema):
            """Load the headers or return `missing` if no value can be found.
            """
            return missing

        def load_cookies(self, req, schema):
            """Load the cookies from the request or return `missing` if no value
            can be found.
            """
            return missing

        def load_files(self, req, schema):
            """Load files from the request or return `missing` if no values can be
            found.
            """
            return missing

        def handle_error(self, error, req, schema, *, error_status_code, error_headers):
            """Called if an error occurs while parsing args. By default, just logs and
            raises ``error``.
            """
            logger.error(error)
            raise error