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"""
All fields that are attached to the models.
The core design of django-parler is to attach descriptor fields
to the shared model, which then proxies the get/set calls to the translated model.
The :class:`TranslatedField` objects are automatically added to the shared model,
but may be added explicitly as well. This also allows to set the ``any_language`` configuration option.
It's also useful for abstract models; add a :class:`TranslatedField` to
indicate that the derived model is expected to provide that translatable field.
"""
from django.core.exceptions import ImproperlyConfigured
from django.db import models
from django.db.models.fields.related_descriptors import ForwardManyToOneDescriptor
from django.forms.utils import pretty_name
def _validate_master(new_class):
"""
Check whether the 'master' field on a TranslatedFieldsModel is correctly configured.
"""
if not new_class.master or not isinstance(new_class.master, ForwardManyToOneDescriptor):
raise ImproperlyConfigured(
f"{new_class.__name__}.master should be a ForeignKey to the shared table."
)
remote_field = new_class.master.field.remote_field
shared_model = remote_field.model
# Skip checks in migration
if shared_model.__module__ == "__fake__":
return shared_model
try:
meta = shared_model._parler_meta
except AttributeError:
raise TypeError(
f"Translatable model {shared_model} does not appear to inherit from TranslatableModel"
)
if meta is not None:
if meta._has_translations_model(new_class):
raise ImproperlyConfigured(
f"The model '{shared_model.__name__}' already has an associated translation table!"
)
if meta._has_translations_field(remote_field.related_name):
raise ImproperlyConfigured(
f"The model '{shared_model.__name__}' already has an associated translation field named '{remote_field.related_name}'!"
)
return shared_model
class TranslationsForeignKey(models.ForeignKey):
"""
Foreign Key field that adds translations to the `to` model.
"""
def contribute_to_related_class(self, cls, related):
from parler.models import TranslatedFieldsModelMixin
super().contribute_to_related_class(cls, related)
_validate_master(self.model)
if issubclass(self.model, TranslatedFieldsModelMixin):
self.model.contribute_translations(cls)
# TODO: inherit RelatedField?
class TranslatedField:
"""
Proxy field attached to a model.
The field is automatically added to the shared model.
However, this can be assigned manually to be more explicit, or to pass the ``any_language`` value.
The ``any_language=True`` option causes the attribute to always return a translated value,
even when the current language and fallback are missing.
This can be useful for "title" attributes for example.
Example:
.. code-block:: python
from django.db import models
from parler.models import TranslatableModel, TranslatedFieldsModel
class MyModel(TranslatableModel):
title = TranslatedField(any_language=True) # Add with any-fallback support
slug = TranslatedField() # Optional, but explicitly mentioned
class MyModelTranslation(TranslatedFieldsModel):
# Manual model class:
master = models.ForeignKey(MyModel, related_name='translations', null=True)
title = models.CharField("Title", max_length=200)
slug = models.SlugField("Slug")
"""
def __init__(self, any_language=False):
self.model = None
self.name = None
self.any_language = any_language
self._meta = None
def contribute_to_class(self, cls, name, **kwargs):
# super().contribute_to_class(cls, name)
self.model = cls
self.name = name
# Add the proxy attribute
setattr(cls, self.name, TranslatedFieldDescriptor(self))
@property
def meta(self):
if self._meta is None:
self._meta = self.model._parler_meta._get_extension_by_field(self.name)
return self._meta
class TranslatedFieldDescriptor:
"""
Descriptor for translated attributes.
This attribute proxies all get/set calls to the translated model.
"""
def __init__(self, field):
"""
:type field: TranslatedField
"""
self.field = field
def __get__(self, instance, instance_type=None):
if not instance:
# Return the class attribute when asked for by the admin.
return self
# Auto create is useless for __get__, will return empty titles everywhere.
# Better use a fallback instead, just like gettext does.
translation = None
meta = self.field.meta
try:
translation = instance._get_translated_model(use_fallback=True, meta=meta)
except meta.model.DoesNotExist as e:
if self.field.any_language:
translation = instance._get_any_translated_model(
meta=meta
) # returns None on error.
if translation is None:
# Improve error message
e.args = (f"{e.args[0]}\nAttempted to read attribute {self.field.name}.",)
raise
return getattr(translation, self.field.name)
def __set__(self, instance, value):
if instance is None:
raise AttributeError(f"{self.field.opts.object_name} must be accessed via instance")
# When assigning the property, assign to the current language.
# No fallback is used in this case.
translation = instance._get_translated_model(
use_fallback=False, auto_create=True, meta=self.field.meta
)
setattr(translation, self.field.name, value)
def __delete__(self, instance):
# No autocreate or fallback, as this is delete.
# Rather blow it all up when the attribute doesn't exist.
# Similar to getting a KeyError on `del dict['UNKNOWN_KEY']`
translation = instance._get_translated_model(meta=self.field.meta)
delattr(translation, self.field.name)
def __repr__(self):
return f"<{self.__class__.__name__} for {self.field.model.__name__}.{self.field.name}>"
@property
def short_description(self):
"""
Ensure that the admin ``list_display`` renders the correct verbose name for translated fields.
The :func:`~django.contrib.admin.utils.label_for_field` function
uses :func:`~django.db.models.Options.get_field_by_name` to find the find and ``verbose_name``.
However, for translated fields, this option does not exist,
hence it falls back to reading the attribute and trying ``short_description``.
Ideally, translated fields should also appear in this list, to be treated like regular fields.
"""
translations_model = self.field.meta.model
if translations_model is None:
# This only happens with abstract models. The code is accessing the descriptor at the base model directly,
# not the upgraded descriptor version that contribute_translations() installed.
# Fallback to what the admin label_for_field() would have done otherwise.
return pretty_name(self.field.name)
field = translations_model._meta.get_field(self.field.name)
return field.verbose_name
class LanguageCodeDescriptor:
"""
This is the property to access the ``language_code`` in the ``TranslatableModel``.
"""
def __get__(self, instance, instance_type=None):
if not instance:
return self
return instance._current_language
def __set__(self, instance, value):
raise AttributeError(
"The 'language_code' attribute cannot be changed directly! Use the set_current_language() method instead."
)
def __delete__(self, instance):
raise AttributeError("The 'language_code' attribute cannot be deleted!")
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