Write correct GraphQL client code with Apollo GraphQL and JavaScript/TypeScript

What is Apollo GraphQL?

Apollo GraphQL is an open-source platform that provides a set of tools and libraries for building and consuming GraphQL APIs. The platform offers a client library for building GraphQL-enabled applications, which allows developers to easily query and mutate data from a GraphQL server. The Apollo client library is available for various programming languages and frameworks, such as JavaScript, React, Angular, and Vue.js. This allows developers to easily integrate GraphQL into their existing applications, regardless of the technology stack they are using.

In addition to the client library, Apollo also provides a server library for building GraphQL servers. The Apollo server library is available for various languages and frameworks, such as JavaScript, Node.js, Python, and Java. The server library provides a simple and flexible way to define a GraphQL schema, handle authentication and authorization, and integrate with various data sources, such as databases, REST APIs, and cloud services. Apollo also provides a set of developer tools and services, such as a GraphQL playground, caching and performance optimization, and real-time subscriptions. These tools and services make it easy for developers to build, test, and optimize their GraphQL APIs.

In the following article, we focus on the Apollo CLIENT library.

What are the common errors when using Apollo GraphQL?

There are several common errors that can occur when using Apollo GraphQL:

1. Syntax errors in the GraphQL query or mutation: These occur when the query or mutation has a syntax error, such as a missing or extra bracket, or an incorrect field name.
2. Validation errors in the GraphQL schema: These occur when the query or mutation tries to access a field or type that is not defined in the GraphQL schema.
3. Authorization errors: These occur when the query or mutation is not authorized to access certain data, usually because the user does not have the correct permissions.
4. Data fetching errors: These occur when there is an issue with retrieving the data from the data source, such as a network error or a database error.
5. Caching errors: These occur when the Apollo client cache is not configured correctly, causing stale or inconsistent data to be returned.
6. Resolver errors: These occur when there is an issue with the resolver function that is responsible for fetching the data for a specific field, such as a bug or a misconfiguration.
7. Type errors: These occur when variables passed to the query or mutation are of the wrong type or do not match the expected shape.
8. Security errors: These occur when there is an issue with the security implementation, such as not properly sanitizing inputs or not validating user's input.

It's important to have proper error handling in place to catch and handle these errors, as well as to log them for debugging and troubleshooting purposes.

How to avoid making errors when using Apollo GraphQL?

Codiga provides a set of rules that detects and autofix coding issues with the Apollo GraphQL library.

In particular, it checks for:

• Data fetching errors: verify that developers are using the loading and error state when using the useQuery and useMutation hooks. The rules also check that the correct fetch policy is being used.
• Caching errors: ensure that the polling interval is not too short when refreshing queries.

To use Codiga and ensure you check your GraphQL code:

1. Download Codiga for your IDE
   • VS Code
   • JetBrains
   • VisualStudio
2. Add a codiga.yml file at the root of your project with the content below (you will be using the apollo-graphql-client-javascript ruleset)

You can also use the following command line

COPYnpx @codiga/cli ruleset-add apollo-graphql-client-javascript

If you also want to check your code at each pull and push request, install Codiga on your repository as well:

• GitHub
• GitLab
• Bitbucket

You can explore the rules and test them yourself by visiting the ruleset on the Codiga Hub.