"""
Helper functions for mapping model fields to a dictionary of default
keyword arguments that should be used for their equivalent serializer fields.
"""
import inspect
from django.core import validators
from django.db import models
from django.utils.text import capfirst
from rest_framework.compat import DecimalValidator
from rest_framework.validators import UniqueValidator
NUMERIC_FIELD_TYPES = (
models.IntegerField, models.FloatField, models.DecimalField
)
class ClassLookupDict(object):
"""
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
from the dictionary or raises a KeyError if nothing matches.
"""
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):
if cls in self.mapping:
return self.mapping[cls]
raise KeyError('Class %s not found in lookup.' % base_class.__name__)
def __setitem__(self, key, value):
self.mapping[key] = value
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)
# The following will only be used by ModelField classes.
# Gets removed for everything else.
kwargs['model_field'] = model_field
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
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'}
if isinstance(model_field, models.AutoField) or not model_field.editable:
# If this field is read-only, then return early.
# Further keyword arguments are not valid.
kwargs['read_only'] = True
return kwargs
if model_field.has_default() or model_field.blank or model_field.null:
kwargs['required'] = False
if model_field.null and not isinstance(model_field, models.NullBooleanField):
kwargs['allow_null'] = True
if model_field.blank and (isinstance(model_field, models.CharField) or
isinstance(model_field, models.TextField)):
kwargs['allow_blank'] = True
if isinstance(model_field, models.FilePathField):
kwargs['path'] = model_field.path
if model_field.match is not None:
kwargs['match'] = model_field.match
if model_field.recursive is not False:
kwargs['recursive'] = model_field.recursive
if model_field.allow_files is not True:
kwargs['allow_files'] = model_field.allow_files
if model_field.allow_folders is not False:
kwargs['allow_folders'] = model_field.allow_folders
if model_field.choices:
# If this model field contains choices, then return early.
# Further keyword arguments are not valid.
kwargs['choices'] = model_field.choices
return kwargs
# Our decimal validation is handled in the field code, not validator code.
# (In Django 1.9+ this differs from previous style)
if isinstance(model_field, models.DecimalField) and DecimalValidator:
validator_kwarg = [
validator for validator in validator_kwarg
if not isinstance(validator, DecimalValidator)
]
# 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) or
isinstance(model_field, models.TextField)):
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.
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):
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):
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):
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
]
# IPAddressField do not need to include the 'validate_ipv46_address' argument,
if isinstance(model_field, models.GenericIPAddressField):
validator_kwarg = [
validator for validator in validator_kwarg
if validator is not validators.validate_ipv46_address
]
if getattr(model_field, 'unique', False):
unique_error_message = model_field.error_messages.get('unique', None)
if unique_error_message:
unique_error_message = unique_error_message % {
'model_name': model_field.model._meta.verbose_name,
'field_label': model_field.verbose_name
}
validator = UniqueValidator(
queryset=model_field.model._default_manager,
message=unique_error_message)
validator_kwarg.append(validator)
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, to_field, has_through_model, reverse = relation_info
kwargs = {
'queryset': related_model._default_manager,
'view_name': get_detail_view_name(related_model)
}
if to_many:
kwargs['many'] = True
if to_field:
kwargs['to_field'] = to_field
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 = model_field.help_text
if help_text:
kwargs['help_text'] = help_text
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:
kwargs['required'] = False
if model_field.null:
kwargs['allow_null'] = True
if model_field.validators:
kwargs['validators'] = model_field.validators
if getattr(model_field, 'unique', False):
validator = UniqueValidator(queryset=model_field.model._default_manager)
kwargs['validators'] = kwargs.get('validators', []) + [validator]
if to_many and not model_field.blank:
kwargs['allow_empty'] = False
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)
}