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Asked: 2024-09-27T13:29:27+05:30 In:

I am encountering an issue with AWS GraphQL where I am getting a “coerced null value” error for a non-nullable input type. Specifically, I am unsure how to properly pass variables to my mutation without triggering this error. Can anyone provide guidance on how to avoid this problem or any best practices for handling non-null inputs in AWS GraphQL?

I’ve been working on an AWS GraphQL project, and I keep running into this frustrating “coerced null value” error whenever I try to use a non-nullable input type in my mutations. It’s really throwing a wrench in my plans, and I’m not sure how to sort it out!

Here’s what I’ve been doing: I have a mutation set up for adding new users, and I’ve defined a user input type that requires a few fields to be non-nullable, like `username` and `email`. However, when I call the mutation, I sometimes end up getting this “coerced null value” error, and it’s driving me nuts.

I checked my data, and it looks like I’m providing values for those non-nullable fields. I even added some logging before the mutation call to make sure everything is being populated correctly. But I still can’t figure out why it sometimes works and other times it doesn’t.

I’m starting to wonder if there’s something I’m missing in the way I pass the variables to the mutation. I’m using the Apollo Client for this, so I’m building my mutation like this:

“`javascript
const ADD_USER = gql`
mutation addUser($input: UserInput!) {
addUser(input: $input) {
id
username
email
}
}
`;
“`

And then I’m calling it like this:

“`javascript
await client.mutate({
mutation: ADD_USER,
variables: {
input: {
username: usernameValue,
email: emailValue,
},
},
});
“`

I thought I had everything in place, but the error keeps popping up, especially if the `usernameValue` or `emailValue` happens to be `undefined` at any point. It seems like there’s a subtlety I’m missing when validating or preparing the values before the mutation call.

So, I’m reaching out to see if anyone else has faced this issue and how you managed to solve it? Are there any tips or best practices I should follow to ensure that I’m correctly handling non-nullable inputs in AWS GraphQL? Any insight would be super helpful. Thanks!

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    2 Answers

    1. Dealing with “Coerced Null Value” Errors in AWS GraphQL

      It sounds like you’re having a rough time with that “coerced null value” error! That can really get annoying. It’s great that you’ve already checked that you’re passing values for `username` and `email`, but there might be a couple of sneaky things causing the issue.

      Here are a few things to consider:

      • Check for Undefined Values: If `usernameValue` or `emailValue` is ever `undefined`, that will throw the error you’re seeing. Before you call the mutation, you might want to log these values right before the mutation to confirm they’re always defined:

        console.log("Username:", usernameValue, "Email:", emailValue);
      • Default Fallbacks: You can set default values for `usernameValue` and `emailValue` if they end up being `undefined`. Just make sure your code handles those cases gracefully:

        const usernameValue = usernameValue || "defaultUsername";
        const emailValue = emailValue || "default@example.com";
      • Confirm Input Type: Check how you’ve defined your UserInput type in your GraphQL schema. If either field can be optional in some cases, you need to define them that way. If they’re truly required, ensure you validate or sanitize your input before sending it in the mutation.
      • Apollo Client Caching: Sometimes Apollo Client caching can cause issues if you’re not updating the cache correctly. If you’re mutating data, ensure you are managing the cache after performing the mutation.

      Overall, just make sure the values are always set before the mutation call. It can definitely be tricky to catch these kinds of issues, but with a bit more logging and checks, you should be able to sort it out!

      Good luck, and don’t hesitate to reach out if you hit more bumps in the road!

    2. The “coerced null value” error typically arises in GraphQL when you try to pass a value that is undefined or null to a field that is defined as non-nullable. In your case, the issue seems to stem from the fact that `usernameValue` and `emailValue` might be undefined at some point before the mutation is called. To mitigate this issue, you should implement additional checks before invoking the mutation to ensure that these values are neither undefined nor null. One straightforward approach is to use a condition that throws an error or logs a message if the values are not populated correctly, thus preventing the mutation from executing with invalid input.

      Additionally, consider using a combination of default values and validation to ensure that your input meets the required criteria for non-nullable fields. You could create a utility function that validates your input before the mutation, ensuring that fields like `username` and `email` are always provided with valid values. For instance, you could write a simple check that throws an error if values are missing, helping you catch errors early in the execution pipeline. By validating the inputs and handling potential undefined values up front, you can significantly reduce the occurrences of coercion errors and streamline your mutation calls.

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