marshmallow schema validation

Question

I have the following Joi schema validation in my node project, which I am planning to convert into python using marshmallow library.

Joi Schema:

aws_access_key: Joi.string().label('AWS ACCESS KEY').required().token().min(20),
aws_secret_key: Joi.string().label('AWS SECRET KEY').required().base64().min(40),
encryption: Joi.string().label('AWS S3 server-side encryption').valid('SSE_S3', 'SSE_KMS', 'CSE_KMS').optional(),
kmsKey: Joi.string().label('AWS S3 server-side encryption KMS key').when('encryption', { is: Joi.valid('SSE_KMS', 'CSE_KMS'), then: Joi.string().required() })

Here is what I did so far using marshmallow in python

from marshmallow import Schema, fields
from marshmallow.validate import OneOf, Length


class AWSSchema(Schema):
   aws_access_key = fields.String("title", required=True, validate=Length(min=20))
   aws_secret_key = fields.String(required=True, validate=Length(min=40))
   encryption = fields.String(required=False, validate=OneOf(['SSE_S3', 'SSE_KMS', 'CSE_KMS']))
   kmskey = fields.String(validate=lambda obj: fields.String(required=True) if obj['encryption'] in ('SSE_KMS', 'CSE_KMS') else fields.String(required=False))


demo = {
 "aws_access_key": "AKXXXXXXXXXXXXXXXXXXX",
 "aws_secret_key": "YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY",
 "encryption_type": "SSE_KMS"
}


schema = AWSSchema()
print(schema.dump(demo))

if encryption_type value is set to SSE_KMS or CSE_KMS, then I need kmskey field should be required field. But the validation is not working as expected. Any help is appreciated?

What do you mean by validation is not working? How are you trying to validate? — PoP, Sep 16 '18 at 05:50
It should be possible to check the existence and value of ksmkey, and then the existence of kmskey, with a top level validator. See https://stackoverflow.com/a/40900980/5781248 — J.J. Hakala, Sep 28 '18 at 08:54

score 0 · Answer 1 · answered Jan 02 '20 at 12:46

Marshmallow has methods you can overwrite to do top-level validation at various points in the dump or load process. The documentation for pre_dump can be found here. Also checkout pre_load and post_dump.

https://marshmallow.readthedocs.io/en/stable/api_reference.html#marshmallow.decorators.pre_dump

marshmallow schema validation

1 Answers1