Question

Imagine a model like this:

class CFile(models.Model):
   filepath   = models.FileField(upload_to=...)
   collection = models.ForeignKey("FileCollection",null=True)
   ... # other attributes that are not relevant

   def clean(self):
     bname = os.path.basename
     if self.collection:
       cfiles = self.baseline.attachment_set.all()
       with_same_basename = filter(lambda e: bname(e.filepath.path) == bname(self.filepath.path),cfiles)
       if len(with_same_basename) > 0:
         raise ValidationError("There already exists a file with the same name in this collection")   

class FileCollection(models.Model):
  name = models.CharField(max_length=255)
  files= models.ManyToManyField("CFile")

I want to disallow the upload of a CFile if there already exists a CFile with the same basename, that’s why I added the clean. The problem is:

• I upload a CFile, with the name file1.png -> gets uploaded because no other files with this name exist
• I upload another CFile, with the name file1.png -> I get the expected error that I already have a file with this name. So, I try to change the file, and upload a file with a different name ( file2.png ). The problem is, I stopped via pdb in the clean, and the model instance is still file1.png. I imagine this happens because of my ValidationError and django allows me to “correct my mistake”. The problem is I cannot correct it if I cannot upload another file. How can I handle this?

EDIT: This happens in the admin area, sorry for forgetting to mention this before. I don’t have anything custom ( besides inlines = [ FileInline ] ).

Answer 1

I think the clearest way is to declare another field in your model for filename and make it unique for every collection. Like this:

class CFile(models.Model):
   filepath   = models.FileField(upload_to=...)
   collection = models.ForeignKey("FileCollection",null=True, related_name='files')
   filename = models.CharField(max_length=255)
   ... # other attributes that are not relevant

    class Meta:
        unique_together = (('filename', 'collection'),)

    def save(self, *args, **kwargs):
        self.filename = bname(self.filepath.path)
        super(CFile, self).save(args, kwargs)