Django rest framework: Is there a way to clean data before validating it with a serializer? - serialization

Question

I've got an API endpoint POST /data.
The received data is formatted in a certain way which is different from the way I store it in the db.
I'll use geometry type from postgis as an example.
class MyPostgisModel(models.Model):
...
position = models.PointField(null=True)
my_charfield = models.CharField(max_length=10)
...
errors = JSONField() # Used to save the cleaning and validation errors
class MyPostgisSerializer(serializers.ModelSerializer):
class Meta:
model = MyPostgisModel
fields = [
...
"position",
...
"my_charfield",
"errors",
]
def to_internal_value(self, data):
...
# Here the data is coming in the field geometry but in the db, it's called
# position. Moreover I need to apply the `GEOSGeometry(json.dumps(...))`
# method as well.
data["position"] = GEOSGeometry(json.dumps(data["geometry"]))
return data
The problem is that there is not only one field like position but many. And I would like (maybe wrongly) to do like the validate_*field_name* scheme but for cleaning (clean_*field_name*).
There is another problem. In this scheme, I would like to still save the rest of the data in the database even if some fields have raised ValidationError (eg: a CharField that is too long) but are not part of the primary_key/a unique_together constraint. And save the related errors into a JSONField like this:
{
"cleaning_errors": {
...
"position": 'Invalid format: {
"type": "NotAValidType", # Should be "Point"
"coordinates": [
4.22,
50.67
]
}'
...
},
"validating_errors": {
...
"my_charfield": "data was too long: 'this data is way too long for 10 characters'",
...
}
}
For the first problem, I thought of doing something like this:
class BaseSerializerCleanerMixin:
"""Abstract Mixin that clean fields."""
def __init__(self, *args, **kwargs):
"""Initialize the cleaner strategy."""
# This is the error_dict to be filled by the `clean_*field_name*`
self.cleaning_error_dict = {}
super().__init__(*args, **kwargs)
def clean_fields(self, data):
"""Clean the fields listed in self.fields_to_clean before validating them."""
cleaned_data = {}
for field_name in getattr(self.Meta, "fields", []):
cleaned_field = (
getattr(self, "clean_" + field_name)(data)
if hasattr(self, "clean_" + field_name)
else data.get(field_name)
)
if cleaned_field is not None:
cleaned_data[field_name] = cleaned_field
return cleaned_data
def to_internal_value(self, data):
"""Reformat data to put it in the database."""
cleaned_data = self.clean_fields(data)
return super().to_internal_value(cleaned_data)
I'm not sure that's a good idea and maybe there is an easy way to deal with such things.
For the second problem ; catching the errors of the validation without specifying with is_valid() returning True when no primary_key being wrongly formatted, I'm not sure how to proceed.