Cannot make optional mutation argument

According to the docs args are optional by default:

class RechargeSim(graphene.Mutation):
    class Arguments:
        msisdn = graphene.String(required=True)
        network_id = graphene.String(required=True)
        product_id = graphene.String()
        airtime_amount = graphene.Float()

Here is a query:

           result = authed_graphql_client.execute(
                '''
                mutation($msisdn: String!, $networkId: String!, $productId: String!) {
                  rechargeSim(msisdn: $msisdn,
                              networkId: $networkId,
                              productId: $productId) {
                    rechargeId
                    message
                  }
                }
                ''',
                variable_values={
                    'msisdn': sim.msisdn,
                    'networkId': network_id,
                    'productId': product_id
                }
            )

I get this error: TypeError: mutate() missing 1 required positional argument: 'airtime_amount'

I have tried the following variations:

class RechargeSim(graphene.Mutation):
    class Arguments:
        msisdn = graphene.String(required=True)
        network_id = graphene.String(required=True)
        product_id = graphene.String()
        airtime_amount = graphene.Float(required=False)```

class RechargeSim(graphene.Mutation):
    class Arguments:
        msisdn = graphene.String(required=True)
        network_id = graphene.String(required=True)
        product_id = graphene.String()
        airtime_amount = graphene.Float(default_value=None)```

class RechargeSim(graphene.Mutation):
    class Arguments:
        msisdn = graphene.String(required=True)
        network_id = graphene.String(required=True)
        product_id = graphene.String()
        airtime_amount = graphene.Float(required=False, default_value=None)```

In the end I have hacked around this by defaulting the value to 0 and then resetting it to None in the resolver if 0.

[jkimbo]

Yep so because airtime_amount is an optional field, when it is not provided in your mutation it won’t be passed to your mutate function and that is causing the error. Replace your mutate function def with:

def mutate(root, info, msisdn, network_id, **kwargs):
	product_id = kwargs.get('product_id', None)
	airtime_amount = kwargs.get('airtime_amount', None)

The reason why it’s not passed to your mutate function if it’s not defined is so that you can differentiate between it being ‘undefined’ and it being null.

[jonahmolinski]

@larsblumberg Seconded. Null values are dropped and there is no way to differentiate between null and undefined.

@jkimbo Has something changed that has caused the functionality of undefined/null to stop working?