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Error whikle making existing fields translatable - model already has a field #154

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an0o0nym opened this issue Aug 31, 2016 · 6 comments
Open

Error whikle making existing fields translatable - model already has a field #154

an0o0nym opened this issue Aug 31, 2016 · 6 comments

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@an0o0nym
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I am trying to translate already existing fields on a model class. I got stuck at the very first step, which is subclassing TranslatableModel class in Category class, and adding TranslatedFields wrapper to translate selected model fields. I am following a book 'Django by Example' as well as the django-parler instructions on how to do that, however when I run manage.py makemigrations myapp "add_translation_model" I am getting the following error :

File ..../env/lib/python3.5/site-packages/parler/models.py", line 965, in contribute_translations
raise TypeError("The model '{0}' already has a field named '{1}'".format(shared_model.__name__, name))
TypeError: The model 'Category' already has a field named 'name'

before applying django-parler:

# models.py
class Category(models.Model):
    name = models.CharField(max_length=200,
                            db_index=True)
    slug = models.SlugField(max_length=200,
                            unique=True)
    class Meta:
        ordering = ('name',)
        verbose_name = 'category'
        verbose_name_plural = 'categories'

    def __str__(self):
        return self.name

    def get_absolute_url(self):
        return reverse('shop:product_list_by_category',
                       args=[self.slug])

after applying django-parler:

# models.py
class Category(TranslatableModel):
    name = models.CharField(max_length=200,
                            db_index=True)
    slug = models.SlugField(max_length=200,
                            unique=True)
    translations = TranslatedFields(
        name = models.CharField(max_length=200,
                                db_index=True),
        slug = models.SlugField(max_length=200,
                                unique=True),
    )
    class Meta:
        # ordering = ('name',)
        verbose_name = 'category'
        verbose_name_plural = 'categories'

    def __str__(self):
        return self.name

    def get_absolute_url(self):
        return reverse('shop:product_list_by_category',
                       args=[self.slug])

I am using Django 1.10.
@vglfr
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vglfr commented Jun 12, 2017

Same problem, my workaround:

  • rename names * to *_t inside translations tuple
  • makemigrations
  • manually rename *_t back to * in migration files

@floa93 floa93 mentioned this issue Sep 20, 2019
Open
@ruohola ruohola mentioned this issue Apr 7, 2020
Merged
@Rashidov21
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is not working with django 3.1

@stefanw
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Contributor

stefanw commented Feb 3, 2021 •
edited

It looks like this check:

if not isinstance(shared_field, (models.Field, TranslatedFieldDescriptor)):
    raise TypeError("The model '{0}' already has a field named '{1}'".format(shared_model.__name__, name))

does not work with Django 3.1. getattr(shared_model, name) returns a django.db.models.query_utils.DeferredAttribute and thus fails the test for being a model field. The comment above it seems outdated.

           # Currently not allowing to replace existing model fields with translatable fields.
           # That would be a nice feature addition however.

My work around was:

  • prefix existing fields with e.g. _ to create a rename migration
  • add translation fields with original field names
  • create data migration between prefixed fields and translation model
  • remove prefixed fields

@akikoskinen akikoskinen mentioned this issue Jan 25, 2022
Merged
@h3x4git
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h3x4git commented Sep 27, 2022

This is still an issue

h3x4git added a commit to h3x4git/django-parler that referenced this issue Sep 27, 2022
@h3x4git
Fixes django-parler#154
46d08de 
This is a simple fix as @stefanw detected the problem
@h3x4git
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h3x4git commented Sep 27, 2022 •
edited

#324
django.db.models.query_utils.DeferredAttribute offers access to the .field from Django 3, so I propose a pull request.
Honestly I don't understand under which Django versions this did actually work

@i-salameh95
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any update on this?

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6 participants
@stefanw @an0o0nym @vglfr @h3x4git @Rashidov21 @i-salameh95