ReactJS

Introducing TanStack Query v5: A Leap Forward in Simplicity and Functionality

Mattia Magi

Nov 16, 2023

3 min read

TanStack Query

TanStack Query v5: A Leap Forward in Simplicity and Functionality

Introduction:

Here at ThisDot we totally love TanStack Query, so we are really excited to share the news about the release of TanStack Query v5, the latest version of the powerful data-fetching library. The TanStack Query team has been hard at work, making significant improvements to enhance the library's usability and functionality. This blog post will explore the exciting new features and changes introduced in v5.

Breaking Changes:

One of the most notable changes in TanStack Query v5 is the removal of most overloads from the codebase. Previously, different overloads were used when calling useQuery and other hooks, resulting in inconsistent usage patterns and subpar TypeScript error messages. With the introduction of TypeScript 4.7, the team was able to unify the usage of these hooks, resulting in a more consistent and streamlined API. Now, developers only need to pass a single object, making the API more intuitive and developer-friendly. To assist with the transition, the team has updated the documentation, released an auto-fixable eslint rule, and provided a codemod tool.

New Features:

TanStack Query v5 introduces a range of exciting new features that enhance the data-fetching experience. Let's explore some of them:

Simplified Optimistic Updates: Performing optimistic updates is now easier than ever with the useMutation hook. Developers can leverage the returned variables without manually updating the cache. This streamlined approach simplifies the process and improves efficiency.
Sharable Mutation State: A highly requested feature, the useMutationState hook allows developers to access the state of all mutations across components. This shared state simplifies coordination and management of mutation-related data.

import { useMutation, useMutationState } from 'tanstack-query';

const mutationKey = ['example']

const mutation = useMutation({
	mutationKey,
	mutationFn: (...) => {
		...
	},
})

// In another component
const data = useMutatationState({
// this mutation key needs to match the one of the given mutation ('example' in our case)
	filters: { mutationKey },
	select: (mutation) => mutation.state.data, 
})

1st Class Suspense Support: TanStack Query v5 fully supports suspense for data fetching. Hooks like useSuspenseQuery, useSuspenseInfiniteQuery, and useSuspenseQueries enable seamless integration of suspense in applications, providing a more efficient and intuitive way to handle data fetching.
Streaming with React Server Components: The new version introduces an experimental integration for suspense on the server in Next.js. By leveraging the react-query-next-experimental adapter, developers can initiate data fetching during server-side rendering (SSR) and stream the result to the client, combining interactivity and data synchronization.
Improved Infinite Queries: Infinite Queries now supports prefetching multiple pages simultaneously, allowing developers to optimize performance. Additionally, the maximum number of pages stored in the cache can be specified, providing more control over memory usage.

// infinite query can be prefetched as a normal query
const prefetchExample = async () => 
	await queryClient.prefetchInfiniteQuery({
		queryKey: ['...key name...'],
		queryFn: fetchFn,
		initialPageParam: 0,
		getNextPageParam: (lastPage, pages) => lastPage.nextCursor, // this is needed when you want to prefetch more than one page
		pages: 5 // prefetch the first 5 pages
	})

New Devtools: The Query devtools have been completely rewritten in a framework-agnostic manner, making them accessible to all adapters. With a revamped UI and new features like cache inline editing and light mode, developers can benefit from enhanced debugging capabilities.
Fine-Grained Persistence: Addressing a long-standing discussion, v5 introduces fine-grained persistence with the experimental_createPersister plugin. This plugin enables developers to persist queries individually, offering just-in-time restore capabilities, particularly beneficial for mobile development.
The queryOptions API: With the unified useQuery API, v5 introduces the queryOptions function, enabling type-safe sharing of query definitions between useQuery and imperative methods like queryClient.prefetchQuery. This enhancement improves code maintainability and type safety.

import { queryOptions } from 'tanstack-query'

function groupOptions(){
	return queryOptions({
		queryKey: ['...key name...'],
		queryFn: fetchFn,
		staleTime: ...
	}) 
}

useQuery(groupOptions())
queryClient.prefetchQuery(groupOptions())

Conclusion:

TanStack Query v5 marks a significant milestone in the evolution of the data-fetching library. The breaking changes and new features introduced in this version enhance the developer experience, simplify usage, and open up exciting possibilities for data management. We encourage fellow developers to explore the migration guide, check the docs and leverage the examples provided to make the most of TanStack Query v5. Upgrade today and experience the future of data fetching with TanStack Query!

This Dot Labs is a development consultancy that is trusted by top industry companies, including Stripe, Xero, Wikimedia, Docusign, and Twilio. This Dot takes a hands-on approach by providing tailored development strategies to help you approach your most pressing challenges with clarity and confidence. Whether it's bridging the gap between business and technology or modernizing legacy systems, you’ll find a breadth of experience and knowledge you need. Check out how This Dot Labs can empower your tech journey.

Mattia Magi

Functional Programming in TypeScript using the fp-ts Library: Exploring Task and TaskEither Operators

Introduction: Welcome back to our blog series on Functional Programming in TypeScript using the fp-ts library. In the previous three blog posts, we covered essential concepts such as the pipe and flow operators, Option type, and various methods and operators like fold, fromNullable, getOrElse, map, flatten, and chain. In this fourth post, we will delve into the powerful Task and TaskEither operators, understanding their significance, and exploring practical examples to showcase their usefulness. Understanding Task and TaskEither: Before we dive into the examples, let's briefly recap what Task and TaskEither are and why they are valuable in functional programming. Task: In functional programming, a Task represents an asynchronous computation that may produce a value or an error. It allows us to work with asynchronous operations in a pure and composable manner. Tasks are lazy and only start executing when we explicitly run them. They can be thought of as a functional alternative to Promises. Now, let's briefly introduce the Either type and its significance in functional programming since this concept, merged with Task gives us the full power of TaskEither. Either: Either is a type that represents a value that can be one of two possibilities: a value of type Left or a value of type Right. Conventionally, the Left type represents an error or failure case, while the Right type represents a successful result. Using Either, we can explicitly handle and propagate errors in a functional and composable way. Example: Handling Division with Either Suppose we have a function divide that performs a division operation. Instead of throwing an error, we can use Either to handle the potential division by zero scenario. Here's an example: `ts import { Either, left, right } from 'fp-ts/lib/Either'; const divide: (a: number, b: number) => Either = (a, b) => { if (b === 0) { return left('Error: Division by zero'); } return right(a / b); }; const result = divide(10, 2); result.fold( (error) => console.log(Error: ${error}`), (value) => console.log(Result: ${value}`) ); ` In this example, the divide function returns an Either type. If the division is successful, it returns a Right value with the result. If the division by zero occurs, it returns a Left value with an error message. We then use the fold function to handle both cases, printing the appropriate message to the console. TaskEither: TaskEither combines the benefits of both Task and Either. It represents an asynchronous computation that may produce a value or an error, just like Task, but also allows us to handle potential errors using the Either type. This enables us to handle errors in a more explicit and controlled manner. Examples: Let's explore some examples to better understand the practical applications of Task and TaskEither operators. Example 1: Fetching Data from an API Suppose we want to fetch data from an API asynchronously. We can use the Task operator to encapsulate the API call and handle the result using the Task's combinators. In the example below, we define a fetchData` function that returns a Task representing the API call. We then use the `fold` function to handle the success and failure cases of the Task. If the Task succeeds, we return a new Task with the fetched data. If it fails, we return a Task with an error message. Finally, we use the `getOrElse` function to handle the case where the Task returns `None`. `typescript import { pipe } from 'fp-ts/lib/function'; import { Task } from 'fp-ts/lib/Task'; import { fold } from 'fp-ts/lib/TaskEither'; import { getOrElse } from 'fp-ts/lib/Option'; const fetchData: Task = () => fetch('https://api.example.com/data'); const handleData = pipe( fetchData, fold( () => Task.of('Error: Failed to fetch data'), (data) => Task.of(Fetched data: ${data}`) ), getOrElse(() => Task.of('Error: Data not found')) ); handleData().then(console.log); ` Example 2: Performing Computation with Error Handling Let's say we have a function divide` that performs a computation and may throw an error. We can use TaskEither to handle the potential error and perform the computation asynchronously. In the example below, we define a `divideAsync` function that takes two numbers and returns a TaskEither representing the division operation. We use the `tryCatch` function to catch any potential errors thrown by the `divide` function. We then use the `fold` function to handle the success and failure cases of the TaskEither. If the TaskEither succeeds, we return a new TaskEither with the result of the computation. If it fails, we return a TaskEither with an error message. Finally, we use the `map` function to transform the result of the TaskEither. `typescript import { pipe } from 'fp-ts/lib/function'; import { TaskEither, tryCatch } from 'fp-ts/lib/TaskEither'; import { fold } from 'fp-ts/lib/TaskEither'; import { map } from 'fp-ts/lib/TaskEither'; const divide: (a: number, b: number) => number = (a, b) => { if (b === 0) { throw new Error('Division by zero'); } return a / b; }; const divideAsync: (a: number, b: number) => TaskEither = (a, b) => tryCatch(() => divide(a, b), (error) => new Error(String(error))); const handleComputation = pipe( divideAsync(10, 2), fold( (error) => TaskEither.left(Error: ${error.message}`), (result) => TaskEither.right(Result: ${result}`) ), map((result) => Computation: ${result}`) ); handleComputation().then(console.log); ` In the first example, we saw how to fetch data from an API using Task and handle the success and failure cases using fold and getOrElse functions. This allows us to handle different scenarios, such as successful data retrieval or error handling when the data is not available. In the second example, we demonstrated how to perform a computation that may throw an error using TaskEither. We used tryCatch to catch potential errors and fold to handle the success and failure cases. This approach provides a more controlled way of handling errors and performing computations asynchronously. Conclusion: In this blog post, we explored the Task` and `TaskEither` operators in the `fp-ts` library. We learned that Task allows us to work with asynchronous computations in a pure and composable manner, while TaskEither combines the benefits of Task and Either, enabling us to handle potential errors explicitly. By leveraging the concepts we have covered so far, such as pipe, flow, Option, fold, map, flatten, and chain, we can build robust and maintainable functional programs in TypeScript using the fp-ts library. Stay tuned for the next blog post in this series, where we will continue our journey into the world of functional programming....

Nov 15, 2023

4 mins

TypeScript

Testing a Fastify app with the NodeJS test runner

Introduction Node.js has shipped a built-in test runner for a couple of major versions. Since its release I haven’t heard much about it so I decided to try it out on a simple Fastify API server application that I was working on. It turns out, it’s pretty good! It’s also really nice to start testing a node application without dealing with the hassle of installing some additional dependencies and managing more configurations. Since it’s got my stamp of approval, why not write a post about it? In this post, we will hit the highlights of the testing API and write some basic but real-life tests for an API server. This server will be built with Fastify, a plugin-centric API framework. They have some good documentation on testing that should make this pretty easy. We’ll also add a SQL driver for the plugin we will test. Setup Let's set up our simple API server by creating a new project, adding our dependencies, and creating some files. Ensure you’re running node v20 or greater (Test runner is a stable API as of the 20 major releases) Overview `index.js` - node entry that initializes our Fastify app and listens for incoming http requests on port 3001 `app.js` - this file exports a function that creates and returns our Fastify application instance `sql-plugin.js` - a Fastify plugin that sets up and connects to a SQL driver and makes it available on our app instance Application Code A simple first test For our first test we will just test our servers index route. If you recall from the app.js` code above, our index route returns a 501 response for “not implemented”. In this test, we're using the createApp` function to create a new instance of our Fastify app, and then using the `inject` method from the Fastify API to make a request to the `/` route. We import our test utilities directly from the node. Notice we can pass async functions to our test to use async/await. Node’s assert API has been around for a long time, this is what we are using to make our test assertions. To run this test, we can use the following command: By default the Node.js test runner uses the TAP reporter. You can configure it using other reporters or even create your own custom reporters for it to use. Testing our SQL plugin Next, let's take a look at how to test our Fastify Postgres plugin. This one is a bit more involved and gives us an opportunity to use more of the test runner features. In this example, we are using a feature called Subtests. This simply means when nested tests inside of a top-level test. In our top-level test call, we get a test parameter t` that we call methods on in our nested test structure. In this example, we use `t.beforeEach` to create a new Fastify app instance for each test, and call the `test` method to register our nested tests. Along with `beforeEach` the other methods you might expect are also available: `afterEach`, `before`, `after`. Since we don’t want to connect to our Postgres database in our tests, we are using the available Mocking API to mock out the client. This was the API that I was most excited to see included in the Node Test Runner. After the basics, you almost always need to mock some functions, methods, or libraries in your tests. After trying this feature, it works easily and as expected, I was confident that I could get pretty far testing with the new Node.js core API’s. Since my plugin only uses the end method of the Postgres driver, it’s the only method I provide a mock function for. Our second test confirms that it gets called when our Fastify server is shutting down. Additional features A lot of other features that are common in other popular testing frameworks are also available. Test styles and methods Along with our basic test` based tests we used for our Fastify plugins - `test` also includes `skip`, `todo`, and `only` methods. They are for what you would expect based on the names, skipping or only running certain tests, and work-in-progress tests. If you prefer, you also have the option of using the describe` → `it` test syntax. They both come with the same methods as `test` and I think it really comes down to a matter of personal preference. Test coverage This might be the deal breaker for some since this feature is still experimental. As popular as test coverage reporting is, I expect this API to be finalized and become stable in an upcoming version. Since this isn’t something that’s being shipped for the end user though, I say go for it. What’s the worst that could happen really? Other CLI flags —watch` - https://nodejs.org/dist/latest-v20.x/docs/api/cli.html#--watch —test-name-pattern` - https://nodejs.org/dist/latest-v20.x/docs/api/cli.html#--test-name-pattern TypeScript support You can use a loader like you would for a regular node application to execute TypeScript files. Some popular examples are tsx` and `ts-node`. In practice, I found that this currently doesn’t work well since the test runner only looks for JS file types. After digging in I found that they added support to locate your test files via a glob string but it won’t be available until the next major version release. Conclusion The built-in test runner is a lot more comprehensive than I expected it to be. I was able to easily write some real-world tests for my application. If you don’t mind some of the features like coverage reporting being experimental, you can get pretty far without installing any additional dependencies. The biggest deal breaker on many projects at this point, in my opinion, is the lack of straightforward TypeScript support. This is the test command that I ended up with in my application: I’ll be honest, I stole this from a GitHub issue thread and I don’t know exactly how it works (but it does). If TypeScript is a requirement, maybe stick with Jest or Vitest for now 🙂...

Nov 29, 2023

5 mins

NodeJSTypeScriptTesting