Why error handling differs from REST in GraphQL - See It in Action

Understanding Error Handling Differences Between GraphQL and REST

📖 Scenario: You are working on a web application that uses both REST and GraphQL APIs. You want to understand how error handling works differently in GraphQL compared to REST to improve your API design and debugging skills.

🎯 Goal: Build a simple GraphQL schema and query that demonstrates how errors are handled differently from REST APIs.

📋 What You'll Learn

Create a GraphQL schema with a query that can return data or an error

Add a configuration variable to simulate error conditions

Write the core resolver logic that returns data or an error based on the configuration

Complete the schema with error handling fields to show error messages in the response

💡 Why This Matters

🌍 Real World

Understanding error handling in GraphQL helps developers build APIs that provide clear feedback to clients, improving debugging and user experience.

💼 Career

Many modern web applications use GraphQL APIs. Knowing how to handle errors properly is essential for backend developers, API designers, and full-stack engineers.

1

DATA SETUP: Define a GraphQL schema with a user query returning id and name

Create a GraphQL schema string called schema that defines a User type with fields id (ID!) and name (String!). Also define a Query type with a user field returning User.

GraphQL

schema = '''
# Define User type and Query type with user field
'''
# Your code here

Hint

Define the User type first, then the Query type with a user field.

2

CONFIGURATION: Add a variable simulate_error to control error simulation

Create a boolean variable called simulate_error and set it to True to simulate an error condition in the resolver.

GraphQL

schema = '''
type User {
  id: ID!
  name: String!
}

type Query {
  user: User
}
'''

# Create simulate_error variable
# Your code here

Hint

Just create a variable named simulate_error and assign True.

3

CORE LOGIC: Write a resolver function resolve_user that returns data or raises an error

Define a function called resolve_user that takes no arguments. If simulate_error is True, raise an exception with message 'User not found'. Otherwise, return a dictionary with id set to '1' and name set to 'Alice'.

GraphQL

schema = '''
type User {
  id: ID!
  name: String!
}

type Query {
  user: User
}
'''

simulate_error = True

# Define resolve_user function
# Your code here

Hint

Use an if statement to check simulate_error and raise an exception or return the user dictionary.

4

COMPLETION: Add error handling in the GraphQL execution to show errors in the response

Add code to execute the GraphQL query { user { id name } } using the schema and resolve_user resolver. Capture errors and include them in the response under the errors key, demonstrating how GraphQL returns errors alongside data.

GraphQL

schema = '''
type User {
  id: ID!
  name: String!
}

type Query {
  user: User
}
'''

simulate_error = True

def resolve_user():
    if simulate_error:
        raise Exception('User not found')
    return {'id': '1', 'name': 'Alice'}

# Execute GraphQL query with error handling
# Your code here

Hint

Use graphql_sync and build_schema from the graphql library. Pass root_value with user resolver. Check result.errors and add them to response.