django - Validate file existence

Question

Django 3.1.5

class PhpFile(models.Model):
    subdir = models.CharField(max_length=255,
                          null=False,
                          blank=False,
                          unique=True,
                          verbose_name="Subdir")
    file = models.FileField(upload_to=php_upload_to,
                            verbose_name="PHP file",)


class ReadonlyFiledsForExistingObjectsMixin():
    """
    Disable a field "subdir" when modifying an object,
    but make it required when adding new object.
    """

    def get_readonly_fields(self, request, obj=None):
        if obj:  # editing an existing object
            return self.readonly_fields + ('subdir',)
        return self.readonly_fields



@admin.register(PhpFile)
class PhpFileAdmin(ReadonlyFiledsForExistingObjectsMixin,                   
                   admin.ModelAdmin):
    form = PhpFileForm
    exclude = []


class PhpFileForm(ModelForm):

    def clean_file(self, *args, **kwargs):

        if "file" in self.changed_data:

            uploading_file = self.cleaned_data['file'].name
            subdir = self.cleaned_data['subdir']
            upload_to = get_upload_to(subdir, uploading_file, FILE_TYPES.PHP)
            file = os.path.join(MEDIA_ROOT, upload_to)

            if os.path.isfile(file):
                raise ValidationError(
                    "File already exists. Change its version or don't upload it.")

            return self.cleaned_data['file']  # File doesn't exist.

I want files to be concentrated in subdirs. So, a model contains a subdir field. And I want to check if a file has already been uploaded. If it has been, I raise validation error.

This code works only if I don't use ReadonlyFiledsForExistingObjectsMixin. If I uncomment it, subdir is not visible in the cleaned_data.

Could you help me organize both:

1. Readonly subdir field for existing objects.
2. Validation for existence of a file with such a name.

question from:https://stackoverflow.com/questions/65950908/validate-file-existence

Answer 1

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