Getting error "Nullability Mismatch on variable $fulfillment....." when invoking a graphQL mutation

[Ashfaq_]

Nullability Mismatch on variable $fulfillment and argument fulfillment (FulfillmentV2Input/FulfillmentV2Input!)

After failing to call the fulfillment API using Rest, I went ahead with integrating the same thing using GraphQL but I am unable to understand why I am encountering this error.

Documentation for reference: https://shopify.dev/api/admin-graphql/2022-01/mutations/fulfillmentCreateV2

[Ole_Visionz]

For future readers...

The error is telling us that you gave an argument of type FulfillmentV2Input but fulfillmentCreateV2(fulfillment) needs an argument of type FulfillmentV2Input! (aka a FulfillmentV2Input that can't be null).

So the code that will solve this error looks like this:

const mutation = `mutation fulfillmentCreateV2($fulfillment: FulfillmentV2Input!) {
  fulfillmentCreateV2(fulfillment: $fulfillment) {
    fulfillment {
      trackingInfo {
        url
        number
        company
      }
    }
    userErrors {
      field
      message
    }
  }
}`;