Custom error extensions in GraphQL - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What is the output of this GraphQL error response with custom extensions?

Consider a GraphQL query that triggers an error with custom extensions. What will the error response contain?

GraphQL

{
  "errors": [
    {
      "message": "User not found",
      "extensions": {
        "code": "USER_NOT_FOUND",
        "timestamp": "2024-06-01T12:00:00Z"
      }
    }
  ]
}

A {"errors":[{"message":"User not found","extensions":{"code":"USER_NOT_FOUND","timestamp":"2024-06-01T12:00:00Z"}}]}

B {"data":null,"errors":[{"message":"User not found"}]}

C {"errors":[{"message":"User not found","code":"USER_NOT_FOUND"}]}

D {"errors":[{"message":"User not found","extensions":{"errorCode":"USER_NOT_FOUND"}}]}

💡 Hint

Custom error extensions appear inside the extensions field in the error object.

The GraphQL error response includes a list of errors. Each error can have an extensions field that holds custom data like error codes and timestamps.

🧠 Conceptual

intermediate

Which field in a GraphQL error response holds custom error details?

In GraphQL, where do you put extra information like error codes or debug data in an error response?

A The <code>message</code> field

B The <code>locations</code> field

C The <code>data</code> field

D The <code>extensions</code> field

💡 Hint

Think about where extra metadata about errors is stored.

The extensions field is designed to hold custom error information beyond the basic message.

📝 Syntax

advanced

Identify the invalid GraphQL error extension format

Which of the following GraphQL error objects has an invalid extensions field format?

A {"message":"Timeout","extensions":"TIMEOUT_ERROR"}

B {"message":"Invalid input","extensions":{"code":"BAD_INPUT"}}

C {"message":"Unauthorized","extensions":{"code":"UNAUTH"}}

D {"message":"Not found","extensions":{"code":"NOT_FOUND","retry":true}}

💡 Hint

The extensions field must be an object, not a string.

Option A uses a string for extensions, which is invalid. It must be an object with key-value pairs.

🔧 Debug

advanced

Why does this GraphQL error extension not appear in the client response?

A server returns this error object but the client does not see the extensions field. What is the likely cause?

{
  "errors": [
    {
      "message": "Access denied",
      "extensions": null
    }
  ]
}

A The <code>message</code> field is missing

B The client filters out <code>extensions</code> by default

C The server must send <code>extensions</code> as an object, not null

D GraphQL does not support <code>extensions</code> in errors

💡 Hint

Check the type of the extensions field.

The extensions field must be an object with key-value pairs. Null disables the extensions data.

❓ optimization

expert

How to efficiently include error codes in GraphQL responses for multiple errors?

You want to send multiple errors with custom codes in a GraphQL response. Which approach is best for performance and clarity?

A Omit error codes to reduce response size

B Include a separate <code>extensions</code> object with a <code>code</code> field for each error

C Embed error codes inside the <code>message</code> string for each error

D Send one <code>extensions</code> object at the root with all error codes combined

💡 Hint

Think about how GraphQL error objects are structured.

Each error should have its own extensions object with a code field. This keeps errors clear and easy to handle.