GraphQL error format - Mini Project: Build & Apply

GraphQL Error Format

📖 Scenario: You are building a GraphQL API for a simple online bookstore. When a client sends a query with invalid data or requests a book that does not exist, your API should return errors in the standard GraphQL error format.

🎯 Goal: Create a GraphQL error response that follows the official GraphQL error format, including message, locations, and path fields.

📋 What You'll Learn

Create an error object with a message field describing the error

Include a locations array with line and column numbers where the error occurred

Add a path array showing the query path that caused the error

💡 Why This Matters

🌍 Real World

GraphQL APIs use this error format to inform clients about problems in queries or mutations clearly and consistently.

💼 Career

Understanding GraphQL error formatting is essential for backend developers building APIs and frontend developers handling API errors gracefully.

1

Create the basic error message

Create a JSON object called error with a message field set to "Book not found".

GraphQL

{
  "message": "Book not found"
  // Your code here
}

Hint

The error object must have a message field with the exact text "Book not found".

2

Add error location information

Add a locations field to the error object. It should be an array with one object containing "line": 3 and "column": 5.

GraphQL

{
  "message": "Book not found",
  "locations": [
    {
      "line": 3,
      "column": 5
    }
  ]
  // Your code here
}

Hint

The locations field is an array with one object specifying the line and column numbers.

3

Add the error path

Add a path field to the error object. It should be an array with the strings "queryBook" and "id".

GraphQL

{
  "message": "Book not found",
  "locations": [
    {
      "line": 3,
      "column": 5
    }
  ],
  "path": ["queryBook", "id"]
  // Your code here
}

Hint

The path field shows the query path as an array of strings.

4

Complete the GraphQL error response

Wrap the error object inside a JSON object with the key errors as an array containing the error object.

GraphQL

{
  "errors": [
    {
      "message": "Book not found",
      "locations": [
        {
          "line": 3,
          "column": 5
        }
      ],
      "path": ["queryBook", "id"]
    }
  ]
  // Your code here
}

Hint

The final response wraps the error object inside an errors array.