Custom error extensions in GraphQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are custom error extensions in GraphQL?

Custom error extensions are additional fields added to GraphQL error responses to provide more details about the error, such as error codes or extra context.

intermediate

How do you add custom error extensions in a GraphQL resolver?

You throw an error with an 'extensions' property, for example: <br>throw new ApolloError('Not found', 'NOT_FOUND', { resource: 'User' }) where the third argument adds custom extensions.

beginner

Why use custom error extensions instead of just error messages?

Custom extensions allow clients to programmatically identify error types and handle them differently, improving user experience and debugging.

beginner

What is the standard field name for custom error details in GraphQL errors?

The standard field name is 'extensions'. It is an object that can hold any extra information about the error.

intermediate

Give an example of a custom error extension field you might add.

You might add a field like { code: 'UNAUTHENTICATED', timestamp: '2024-06-01T12:00:00Z' } to indicate the error type and when it happened.

What is the purpose of the 'extensions' field in a GraphQL error?

A To store the query string

B To hold the user's authentication token

C To provide extra structured information about the error

D To define the GraphQL schema

The 'extensions' field holds extra details about the error to help clients understand and handle it.

How do you include custom error extensions when throwing an error in Apollo Server?

A By changing the HTTP status code

B By passing an object as the third argument to ApolloError

C By adding a new query

D By modifying the GraphQL schema

ApolloError accepts a third argument for extensions, allowing you to add custom error details.

Which of these is NOT a good reason to use custom error extensions?

A To store sensitive user passwords

B To provide user-friendly error codes

C To help clients handle errors programmatically

D To add timestamps or context to errors

Sensitive data like passwords should never be included in error extensions.

What type of data can the 'extensions' field contain?

A Any JSON-serializable data

B Only numbers

C Only strings

D Only booleans

The 'extensions' field can hold any data that can be converted to JSON.

If you want to indicate an error is due to authentication failure, which extension code might you use?

A SUCCESS

B NOT_FOUND

C INTERNAL_ERROR

D UNAUTHENTICATED

'UNAUTHENTICATED' is commonly used to indicate authentication errors.

Explain how custom error extensions improve error handling in GraphQL.

Think about why just an error message might not be enough.

Describe how to add custom error extensions in a GraphQL resolver using Apollo Server.

Focus on the ApolloError constructor parameters.