Conditionally required fields in Eve schema

Question

I implemented the recently committed 'dependencies': {'attr': 'val'} support, but it's not working for my use case. Here's what I'd like to do:

schema = {
    'attr1': {'type': 'string', 'required': True, 'allowed': ['Foo', 'Bar']},
    'attr2': {'type': 'integer', 'required': True, 'default': 1,
              'dependencies': {'attr1': 'Foo'}}
}

object = {
    'attr1': 'Bar'
}

When I POST object to an endpoint with schema, it fails with "attr2": "field 'type' is required with values: Foo". I want it to only fail if attr1: 'Foo' as in my dependencies dict.

I think Eve might be populating attr2 with the default value 1 specified in the schema and that's why it's throwing this error, but I'm not sure.

Answer 1

I just tried this on Cerberus 0.8-dev:

from cerberus import Validator

schema = {
    'attr1': {'type': 'string', 'required': True, 'allowed': ['Foo', 'Bar']},
    'attr2': {'type': 'integer', 'required': True, 'dependencies': {'attr1': 'Foo'}}
}

object = {
    'attr1': 'Bar'
}

v = Validator(schema)
v.validate(object)
True

Then I tried:

object = {
    'attr1': 'Bar',
    'attr2': 1
}

v.validate(object)
False

v.errors
{'attr2': "field 'attr1' is required with values: Foo"}

object = {
    'attr1': 'Foo',
    'attr2': 1
}

v.validate(object)
True

Make sure you're on v0.8 though, this won't work on 0.7.2 which is the current release available on PyPI (which also means that this won't be available in Eve until Cerberus 0.8 is released and Eve 0.5 updates its Cerberus requirements).