Validation errors in GraphQL

Introduction

Validation errors help you find mistakes in your GraphQL queries before running them. They make sure your requests follow the rules.

When you write a GraphQL query and want to check if it is correct.

When your app sends data to a GraphQL server and you want to catch wrong inputs early.

When debugging why a GraphQL query is not returning data.

When learning GraphQL and practicing writing queries.

When building tools that help users write GraphQL queries safely.

Syntax

GraphQL

Validation errors are returned by the GraphQL server as part of the response when a query is incorrect.

Example error response:
{
  "errors": [
    {
      "message": "Cannot query field 'wrongField' on type 'User'.",
      "locations": [{"line": 3, "column": 5}]
    }
  ]
}

Validation errors appear in the 'errors' field of the GraphQL response.

They include a message explaining the problem and where it happened in the query.

Examples

This query asks for a field 'wrongField' that does not exist on 'user'. The server will return a validation error.

GraphQL

query {
  user {
    wrongField
  }
}

This query is valid if 'user' accepts an 'id' argument and 'name' is a valid field.

GraphQL

query {
  user(id: "123") {
    name
  }
}

Sample Program

This query tries to get a field that does not exist. The server will respond with a validation error showing the problem.

GraphQL

query {
  user {
    wrongField
  }
}

Important Notes

Always check the 'errors' field in the response to catch validation problems.

Validation errors help you fix queries before they cause bigger issues.

Summary

Validation errors tell you when your GraphQL query is wrong.

They include messages and locations to help you fix mistakes.

Checking validation errors is an important step when working with GraphQL.