React Query Library's ESLint Plugin: Ensuring Best Practices and Code Quality

Anton Ioffe - March 5th 2024 - 10 minutes read

In the ever-evolving landscape of modern web development, maintaining code quality and adhering to best practices isn't just advisable; it's imperative. As React Query continues to shape the way we handle data fetching and state synchronization in React applications, the integration of ESLint stands as a beacon of excellence, guiding developers through the labyrinth of potential pitfalls and inefficiencies. This article unfolds the indispensable synergy between React Query and its ESLint plugin, navigating from the initial setup to the intricate crafting of custom rules. We delve into the common coding mistakes, advanced optimization techniques, and the forward-thinking approach of tailoring ESLint to your project's unique tapestry. Prepare to elevate your code to a realm of unmatched quality and performance, marking a paradigm shift in how you perceive and implement data management within React applications.

Introduction to React Query and ESLint's Role

React Query has revolutionized the way developers handle server-state data in React applications. It abstracts away the complexities related to data fetching, synchronization, and caching, making it simpler to manage server-side state in a predictable way. By enabling efficient data fetching mechanisms, React Query ensures that the UI remains in sync with the server state, reducing the amount of boilerplate code and improving overall application performance.

On the other hand, ESLint stands as a vital tool for maintaining high code quality and consistency across JavaScript and React codebases. It scrutinizes the code for potential issues, enforcing a set of predefined rules that cover everything from syntax errors to best coding practices. This capability makes ESLint an invaluable asset for early error detection and helps in maintaining a clean, maintainable, and bug-free codebase.

In the context of React applications, where code complexity can grow rapidly due to the dynamic nature of user interfaces and data interactions, ESLint plays a crucial role. It aids in identifying common coding mistakes early in the development lifecycle, encourages adherence to best practices, and ensures a unified coding standard across the team. This is particularly beneficial in collaborative environments where consistency in coding styles and practices is critical for the project's success.

Integrating React Query with ESLint brings about a synergy that boosts both the productivity of the development process and the quality of the resulting applications. Through custom rules and plugins designed for React Query, developers can avoid common pitfalls associated with asynchronous data fetching and state management. Moreover, this integration facilitates the adoption of best practices tailored specifically to React Query's patterns and idioms, further enriching the developer experience and application integrity.

Given the complexity of modern web applications, ensuring that both the logic related to data management (handled by React Query) and the overall code quality (ensured by ESLint) maintain the highest standards is crucial. This foundational understanding sets the stage for exploring the integration of React Query with ESLint, promising to elevate the effectiveness and efficiency of developing React applications. Through this lens, we're poised to delve deeper into how ESLint can be leveraged to enforce best practices and ensure code quality in applications powered by React Query.

Setting Up React Query's ESLint Plugin

To kick off the setup for the React Query ESLint plugin, begin by installing the necessary packages. Run the following command in your project's root directory: npm install --save-dev eslint-plugin-react-query. This command adds the ESLint plugin for React Query to your development dependencies, ensuring that your project is equipped to enforce best practices and catch common errors associated with using React Query.

Once the installation is complete, the next step involves integrating the plugin into your ESLint configuration. Open or create an .eslintrc.js file in your project's root and add 'react-query' to the plugins array. This step is crucial as it tells ESLint to include the rules from the React Query plugin when linting your codebase.

In addition to enabling the plugin, you must also configure ESLint to enforce specific React Query rules. In the same .eslintrc.js file, under the rules section, start specifying React Query-related rules you want to enforce. For example, to ensure that query keys are always arrays, you could add a rule like 'react-query/query-key-format': 'error'. Configuring these rules helps maintain consistency and leverages best practices within your React Query usage.

For teams looking to achieve a higher standard of code quality, you might want to be more detailed with the rules you enforce. React Query's ESLint plugin offers a variety of rules that cater to common scenarios encountered in projects using React Query. These settings include but are not limited to ensuring the correct use of query hooks and managing query invalidations properly. Delve into each rule's documentation to understand its purpose and decide which ones align with your project's needs.

Lastly, after setting up and configuring the ESLint plugin for React Query, it’s important to regularly run ESLint checks as part of your development workflow. Incorporating these checks into your continuous integration (CI) pipeline or executing them locally before commits can drastically reduce the introduction of errors and improve code quality over time. Consistently applying and refining your ESLint rules in response to the changing dynamics of your project and React Query's evolution will further enhance the robustness and reliability of your application.

Common code Mistakes in React Query and How ESLint Corrects Them

One common mistake while using React Query is the mishandling of query keys. Query keys are crucial for cache identification and invalidation but are often incorrectly implemented or inconsistently formatted across different components, leading to unnecessary re-fetching and cache duplication. The ESLint plugin for React Query can detect when query keys do not follow a consistent format or when they are prone to typos and duplication—highlighting these as errors or warnings in the code. For example, having a rule that enforces query keys to be arrays with a specific structure ensures consistent identification for cached data, thus optimizing the application's performance and data management.

Incorrect cache configuration is another area where developers commonly err. Configuring cache times and stale times improperly can lead to a mismatch between the user’s interaction and the data displayed, resulting in stale data or overly frequent background updates. The ESLint plugin for React Query steps in by providing rules that enforce best practices for cache settings, guiding developers to set optimal cache timers and avoid common pitfalls in cache configuration. By following these ESLint suggestions, developers can ensure that their application efficiently utilizes React Query's caching mechanism, maintaining a seamless user experience.

Inefficient use of query hooks, such as using useQuery or useMutation without fully utilizing their configurations, or misusing them in scenarios that don’t require their full capabilities, can degrade performance and lead to bugs. Through specific rule sets, the ESLint plugin can identify cases where a simpler hook could be used or where the configuration of a hook could be optimized for the use case at hand. For instance, it can suggest the use of useQueries for parallel queries instead of multiple useQuery calls, or highlight unnecessary query key dependencies that could lead to excessive re-fetching.

Failures to handle query states accurately, such as not properly managing loading, error, and success states, can lead to a poor user experience. The ESLint plugin assists by ensuring all possible states returned by query hooks are addressed in the code. This involves rules that detect missing error boundaries or the absence of loading indicators, helping developers create a more resilient and user-friendly application by handling each state comprehensively.

Lastly, overlooking the importance of query invalidation and updates after data mutations leads to the display of outdated information. Many developers forget to invalidate queries or to correctly configure mutations to update the query cache. ESLint rules targeting React Query usage can catch these oversights, suggesting when and how to invalidate queries or use optimistic updates to keep the application data fresh post-mutation, thereby enhancing the data consistency throughout the application lifecycle. Through these automated checks and balances, the ESLint plugin for React Query significantly aids in maintaining best practices and high code quality in React applications leveraging React Query for state management.

Advanced ESLint Rules for React Query Optimization

One advanced ESLint rule targets the optimization of query prefetching in React Query, a critical aspect for enhancing user experience by loading data before it's actually needed. This rule can help developers identify missed opportunities for query prefetching in their components or misuse of the useQuery hook that leads to delayed data fetching. By enforcing prefetching where it makes the most sense, applications become much snappier. Here’s an illustrative example:

// Bad practice
const { data } = useQuery(['userData', userId], fetchUserData);

// Good practice
useEffect(() => {
  queryClient.prefetchQuery(['userData', userId], fetchUserData);
}, [userId, queryClient]);

In this scenario, the ESLint rule would highlight the direct use of useQuery for fetching user data that could rather be prefetched.

Another rule focuses on ensuring that developers properly implement query caching mechanisms. It checks that queries fetching similar data with slight variations are correctly grouped under a single query key. This avoids unnecessary data refetching, ultimately reducing network load and improving data retrieval speeds. For example:

// Bad practice
const { data: userProfile } = useQuery(`userProfile-${userId}`, fetchUserProfile);
const { data: userPosts } = useQuery(`userPosts-${userId}`, fetchUserPosts);

// Good practice
const userProfileQueryKey = ['user', userId, 'profile'];
const userPostsQueryKey = ['user', userId, 'posts'];
// queries are now identifiable as related through their keys

Proper use and definition of mutation hooks are also crucial in maintaining application performance and consistency. An advanced ESLint rule in this area would ensure that mutations are defined with all necessary options, like onSuccess, for updating related queries post-mutation, thus keeping the cache up to date. Code without these provisions may lead to stale state issues:

// Bad practice
const mutation = useMutation(updateUserData);

// Good practice
const mutation = useMutation(updateUserData, {
  onSuccess: () => {

To safeguard against unnecessary rerenders, a specific ESLint rule can detect components that may incorrectly use query data, causing the component to rerender more often than needed. For instance, destructuring data from a query hook directly in a component’s return statement could trigger rerenders every time the component’s state changes. The rule would flag this pattern, prompting developers to instead use memoization techniques or move data destructuring outside of the high-frequency execution paths.

Finally, an advanced rule might enforce best practices around error handling in data fetching scenarios. Without proper error handling mechanisms in place, applications can exhibit unhelpful behavior or crash during data fetching failures. This rule ensures that all queries and mutations implement an error handling strategy, be it through retry mechanisms or user-friendly error messages, to enhance application resilience.

// Bad practice
const { data, error } = useQuery(['userData', userId], fetchUserData);

// Good practice
const { data, error } = useQuery(['userData', userId], fetchUserData, {
  retry: false, // or a custom retry strategy
  onError: (error) => {
    toast.error(`Fetching user data failed: ${error.message}`);

Through these examples, we see how ESLint rules tailored to React Query can significantly elevate code quality, enforce best practices, and optimize application performance.

Evolving with React Query: Custom ESLint Rules and Best Practices

As the landscape of web development with React evolves, so does the complexity and specificity of the tools we use to maintain code quality and efficiency. This is particularly true for projects leveraging React Query, a powerful library for server-state management in React applications. Given React Query's unique paradigms and patterns, the off-the-shelf ESLint rules might not fully accommodate the specific best practices and pitfalls associated with its use. To bridge this gap, creating custom ESLint rules tailored to React Query's context can dramatically enhance code quality, maintainability, and adherence to best practices.

The rationale behind crafting custom ESLint rules for React Query lies in the library's nuanced handling of server-state data. React Query abstracts many complexities around data fetching, caching, and synchronization, introducing patterns that may not be immediately intuitive to all developers. Custom ESLint rules can guide developers in applying these patterns correctly, preventing common mistakes such as mismanagement of query keys, incorrect invalidation strategies, or inefficient use of React Query's hooks and utilities. By enforcing a consistent approach to these aspects, custom ESLint rules help maintain a high standard of code quality and application performance.

Defining custom ESLint rules requires a deep understanding of both ESLint's API and the best practices associated with React Query. The process typically involves identifying specific code patterns that signify best practices or common errors in the context of React Query and then implementing logic to detect these patterns within the codebase. For instance, a custom rule might enforce the use of array-based query keys, a practice that React Query recommends for maximizing query efficiency and cache management. By formalizing these practices into enforceable rules, teams can ensure that their codebase remains consistent and optimal.

Adapting ESLint rules to accommodate the evolving best practices in React Query development not only enhances code quality but also fosters a culture of continuous improvement and learning within development teams. By engaging in the process of defining and refining custom ESLint rules, developers gain a deeper understanding of React Query's capabilities and limitations. This proactive approach to code quality can lead to more robust, maintainable, and high-quality React applications, as developers are guided away from potential pitfalls and towards more efficient, idiomatic use of React Query.

In conclusion, while ESLint serves as a formidable tool for maintaining code quality across JavaScript and React projects, its true potential is unlocked when it's finely tuned to the unique demands of the tools and libraries in use, such as React Query. Custom ESLint rules represent an advanced strategy, not just for enforcing code standards, but for embedding best practices and nuanced understanding of React Query directly into the development workflow. As React Query continues to evolve, the ongoing development of custom ESLint rules will be crucial in ensuring that projects can rapidly adapt to new patterns and practices, ensuring codebases remain clean, efficient, and maintainable. This dynamic interplay between tooling and library ecosystems encourages developers to think critically about how best to leverage ESLint, React Query, and other tools in harmony, driving forward the quality and performance of modern web applications.


The article discusses the integration of React Query with ESLint to ensure code quality and best practices in modern web development. It highlights the role of ESLint in detecting common coding mistakes and optimizing the use of React Query. The article also introduces advanced ESLint rules for React Query optimization and emphasizes the importance of evolving with React Query by creating custom ESLint rules. The key takeaway is that by leveraging React Query's ESLint plugin, developers can enhance code quality, adhere to best practices, and optimize application performance. A challenging technical task for the reader could be to create a custom ESLint rule for React Query that enforces a specific pattern or best practice not covered by the existing rules.

Don't Get Left Behind:
The Top 5 Career-Ending Mistakes Software Developers Make
FREE Cheat Sheet for Software Developers