django-rest-framework/rest_framework/utils/field_mapping.py

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"""
Helper functions for mapping model fields to a dictionary of default
keyword arguments that should be used for their equivelent serializer fields.
"""
import inspect
from django.core import validators
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from django.db import models
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from django.utils.text import capfirst
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from rest_framework.compat import clean_manytomany_helptext
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from rest_framework.validators import UniqueValidator
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NUMERIC_FIELD_TYPES = (
models.IntegerField, models.FloatField, models.DecimalField
)
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class ClassLookupDict(object):
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"""
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Takes a dictionary with classes as keys.
Lookups against this object will traverses the object's inheritance
hierarchy in method resolution order, and returns the first matching value
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from the dictionary or raises a KeyError if nothing matches.
"""
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def __init__(self, mapping):
self.mapping = mapping
def __getitem__(self, key):
if hasattr(key, '_proxy_class'):
# Deal with proxy classes. Ie. BoundField behaves as if it
# is a Field instance when using ClassLookupDict.
base_class = key._proxy_class
else:
base_class = key.__class__
for cls in inspect.getmro(base_class):
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if cls in self.mapping:
return self.mapping[cls]
raise KeyError('Class %s not found in lookup.' % base_class.__name__)
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def __setitem__(self, key, value):
self.mapping[key] = value
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def needs_label(model_field, field_name):
"""
Returns `True` if the label based on the model's verbose name
is not equal to the default label it would have based on it's field name.
"""
default_label = field_name.replace('_', ' ').capitalize()
return capfirst(model_field.verbose_name) != default_label
def get_detail_view_name(model):
"""
Given a model class, return the view name to use for URL relationships
that refer to instances of the model.
"""
return '%(model_name)s-detail' % {
'app_label': model._meta.app_label,
'model_name': model._meta.object_name.lower()
}
def get_field_kwargs(field_name, model_field):
"""
Creates a default instance of a basic non-relational field.
"""
kwargs = {}
validator_kwarg = list(model_field.validators)
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# The following will only be used by ModelField classes.
# Gets removed for everything else.
kwargs['model_field'] = model_field
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if model_field.verbose_name and needs_label(model_field, field_name):
kwargs['label'] = capfirst(model_field.verbose_name)
if model_field.help_text:
kwargs['help_text'] = model_field.help_text
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max_digits = getattr(model_field, 'max_digits', None)
if max_digits is not None:
kwargs['max_digits'] = max_digits
decimal_places = getattr(model_field, 'decimal_places', None)
if decimal_places is not None:
kwargs['decimal_places'] = decimal_places
if isinstance(model_field, models.TextField):
kwargs['style'] = {'base_template': 'textarea.html'}
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if isinstance(model_field, models.AutoField) or not model_field.editable:
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# If this field is read-only, then return early.
# Further keyword arguments are not valid.
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kwargs['read_only'] = True
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return kwargs
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if model_field.has_default() or model_field.blank or model_field.null:
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kwargs['required'] = False
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if model_field.null and not isinstance(model_field, models.NullBooleanField):
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kwargs['allow_null'] = True
if model_field.blank and (isinstance(model_field, models.CharField) or
isinstance(model_field, models.TextField)):
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kwargs['allow_blank'] = True
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if model_field.choices:
# If this model field contains choices, then return early.
# Further keyword arguments are not valid.
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kwargs['choices'] = model_field.choices
return kwargs
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# Ensure that max_length is passed explicitly as a keyword arg,
# rather than as a validator.
max_length = getattr(model_field, 'max_length', None)
if max_length is not None and isinstance(model_field, models.CharField):
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kwargs['max_length'] = max_length
validator_kwarg = [
validator for validator in validator_kwarg
if not isinstance(validator, validators.MaxLengthValidator)
]
# Ensure that min_length is passed explicitly as a keyword arg,
# rather than as a validator.
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min_length = next((
validator.limit_value for validator in validator_kwarg
if isinstance(validator, validators.MinLengthValidator)
), None)
if min_length is not None and isinstance(model_field, models.CharField):
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kwargs['min_length'] = min_length
validator_kwarg = [
validator for validator in validator_kwarg
if not isinstance(validator, validators.MinLengthValidator)
]
# Ensure that max_value is passed explicitly as a keyword arg,
# rather than as a validator.
max_value = next((
validator.limit_value for validator in validator_kwarg
if isinstance(validator, validators.MaxValueValidator)
), None)
if max_value is not None and isinstance(model_field, NUMERIC_FIELD_TYPES):
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kwargs['max_value'] = max_value
validator_kwarg = [
validator for validator in validator_kwarg
if not isinstance(validator, validators.MaxValueValidator)
]
# Ensure that max_value is passed explicitly as a keyword arg,
# rather than as a validator.
min_value = next((
validator.limit_value for validator in validator_kwarg
if isinstance(validator, validators.MinValueValidator)
), None)
if min_value is not None and isinstance(model_field, NUMERIC_FIELD_TYPES):
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kwargs['min_value'] = min_value
validator_kwarg = [
validator for validator in validator_kwarg
if not isinstance(validator, validators.MinValueValidator)
]
# URLField does not need to include the URLValidator argument,
# as it is explicitly added in.
if isinstance(model_field, models.URLField):
validator_kwarg = [
validator for validator in validator_kwarg
if not isinstance(validator, validators.URLValidator)
]
# EmailField does not need to include the validate_email argument,
# as it is explicitly added in.
if isinstance(model_field, models.EmailField):
validator_kwarg = [
validator for validator in validator_kwarg
if validator is not validators.validate_email
]
# SlugField do not need to include the 'validate_slug' argument,
if isinstance(model_field, models.SlugField):
validator_kwarg = [
validator for validator in validator_kwarg
if validator is not validators.validate_slug
]
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if getattr(model_field, 'unique', False):
validator = UniqueValidator(queryset=model_field.model._default_manager)
validator_kwarg.append(validator)
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if validator_kwarg:
kwargs['validators'] = validator_kwarg
return kwargs
def get_relation_kwargs(field_name, relation_info):
"""
Creates a default instance of a flat relational field.
"""
model_field, related_model, to_many, has_through_model = relation_info
kwargs = {
'queryset': related_model._default_manager,
'view_name': get_detail_view_name(related_model)
}
if to_many:
kwargs['many'] = True
if has_through_model:
kwargs['read_only'] = True
kwargs.pop('queryset', None)
if model_field:
if model_field.verbose_name and needs_label(model_field, field_name):
kwargs['label'] = capfirst(model_field.verbose_name)
help_text = clean_manytomany_helptext(model_field.help_text)
if help_text:
kwargs['help_text'] = help_text
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if not model_field.editable:
kwargs['read_only'] = True
kwargs.pop('queryset', None)
if kwargs.get('read_only', False):
# If this field is read-only, then return early.
# No further keyword arguments are valid.
return kwargs
if model_field.has_default() or model_field.blank or model_field.null:
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kwargs['required'] = False
if model_field.null:
kwargs['allow_null'] = True
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if model_field.validators:
kwargs['validators'] = model_field.validators
if getattr(model_field, 'unique', False):
validator = UniqueValidator(queryset=model_field.model._default_manager)
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kwargs['validators'] = kwargs.get('validators', []) + [validator]
if to_many and not model_field.blank:
kwargs['allow_empty'] = False
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return kwargs
def get_nested_relation_kwargs(relation_info):
kwargs = {'read_only': True}
if relation_info.to_many:
kwargs['many'] = True
return kwargs
def get_url_kwargs(model_field):
return {
'view_name': get_detail_view_name(model_field)
}