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"""
The metadata API is used to allow customization of how `OPTIONS` requests
are handled. We currently provide a single default implementation that returns
some fairly ad-hoc information about the view.
Future implementations might use JSON schema or other definitions in order
to return this information in a more standardized way.
"""
from collections import OrderedDict
from django.core.exceptions import PermissionDenied
from django.http import Http404
from django.utils.encoding import force_text
from rest_framework import exceptions, serializers
from rest_framework.request import clone_request
from rest_framework.utils.field_mapping import ClassLookupDict
class BaseMetadata:
def determine_metadata(self, request, view):
"""
Return a dictionary of metadata about the view.
Used to return responses for OPTIONS requests.
"""
raise NotImplementedError(".determine_metadata() must be overridden.")
class SimpleMetadata(BaseMetadata):
"""
This is the default metadata implementation.
It returns an ad-hoc set of information about the view.
There are not any formalized standards for `OPTIONS` responses
for us to base this on.
"""
label_lookup = ClassLookupDict({
serializers.Field: 'field',
serializers.BooleanField: 'boolean',
serializers.NullBooleanField: 'boolean',
serializers.CharField: 'string',
serializers.UUIDField: 'string',
serializers.URLField: 'url',
serializers.EmailField: 'email',
serializers.RegexField: 'regex',
serializers.SlugField: 'slug',
serializers.IntegerField: 'integer',
serializers.FloatField: 'float',
serializers.DecimalField: 'decimal',
serializers.DateField: 'date',
serializers.DateTimeField: 'datetime',
serializers.TimeField: 'time',
serializers.ChoiceField: 'choice',
serializers.MultipleChoiceField: 'multiple choice',
serializers.FileField: 'file upload',
serializers.ImageField: 'image upload',
serializers.ListField: 'list',
serializers.DictField: 'nested object',
serializers.Serializer: 'nested object',
})
def determine_metadata(self, request, view):
metadata = OrderedDict()
metadata['name'] = view.get_view_name()
metadata['description'] = view.get_view_description()
metadata['renders'] = [renderer.media_type for renderer in view.renderer_classes]
metadata['parses'] = [parser.media_type for parser in view.parser_classes]
if hasattr(view, 'get_serializer'):
actions = self.determine_actions(request, view)
if actions:
metadata['actions'] = actions
return metadata
def determine_actions(self, request, view):
"""
For generic class based views we return information about
the fields that are accepted for 'PUT' and 'POST' methods.
"""
actions = {}
for method in {'PUT', 'POST'} & set(view.allowed_methods):
view.request = clone_request(request, method)
try:
# Test global permissions
if hasattr(view, 'check_permissions'):
view.check_permissions(view.request)
# Test object permissions
if method == 'PUT' and hasattr(view, 'get_object'):
view.get_object()
except (exceptions.APIException, PermissionDenied, Http404):
pass
else:
# If user has appropriate permissions for the view, include
# appropriate metadata about the fields that should be supplied.
serializer = view.get_serializer()
actions[method] = self.get_serializer_info(serializer)
finally:
view.request = request
return actions
def get_serializer_info(self, serializer):
"""
Given an instance of a serializer, return a dictionary of metadata
about its fields.
"""
if hasattr(serializer, 'child'):
# If this is a `ListSerializer` then we want to examine the
# underlying child serializer instance instead.
serializer = serializer.child
return OrderedDict([
(field_name, self.get_field_info(field))
for field_name, field in serializer.fields.items()
if not isinstance(field, serializers.HiddenField)
])
def get_field_info(self, field):
"""
Given an instance of a serializer field, return a dictionary
of metadata about it.
"""
field_info = OrderedDict()
field_info['type'] = self.label_lookup[field]
field_info['required'] = getattr(field, 'required', False)
attrs = [
'read_only', 'label', 'help_text',
'min_length', 'max_length',
'min_value', 'max_value'
]
for attr in attrs:
value = getattr(field, attr, None)
if value is not None and value != '':
field_info[attr] = force_text(value, strings_only=True)
if getattr(field, 'child', None):
field_info['child'] = self.get_field_info(field.child)
elif getattr(field, 'fields', None):
field_info['children'] = self.get_serializer_info(field)
if (not field_info.get('read_only') and
not isinstance(field, (serializers.RelatedField, serializers.ManyRelatedField)) and
hasattr(field, 'choices')):
field_info['choices'] = [
{
'value': choice_value,
'display_name': force_text(choice_name, strings_only=True)
}
for choice_value, choice_name in field.choices.items()
]
return field_info
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