Vite 5 & TS: Fix ESLint Unsafe Call Error With React()

by Luna Greco 55 views

Hey guys! So, we've got a bit of a situation brewing with Vite 5.0, TypeScript, and ESLint. Specifically, some of us are running into an Unsafe call of a(n) 'error' type typed value @typescript-eslint/no-unsafe-call error that seems to pop up when we're using the react() line in our vite.config.ts files. This wasn't an issue back in Vite 4.4.1, so let's break down what's happening and how we can tackle it.

Understanding the Bug

This bug manifests as an ESLint error, specifically Unsafe call of a(n) 'error' type typed value @typescript-eslint/no-unsafe-call. It occurs within a TypeScript Vite configuration (vite.config.ts) when using the react() function, typically part of the @vitejs/plugin-react plugin. The error indicates that ESLint, with the @typescript-eslint/eslint-plugin enabled, is flagging a potentially unsafe function call. This usually means that the type information isn't fully aligned, and TypeScript's strict checks are catching something that might lead to runtime issues. It's crucial to address this because ignoring such errors can lead to unexpected behavior in your application, especially as it grows in complexity. To truly grasp the core of the issue, we need to delve into how Vite, TypeScript, and ESLint interact, and pinpoint where the type mismatch is occurring.

The root cause often lies in the interplay between the versions of Vite, the @vitejs/plugin-react, TypeScript, and the ESLint plugins being used. When these tools aren't perfectly aligned, type definitions can clash, leading to ESLint's no-unsafe-call error. Specifically, the react() function from @vitejs/plugin-react might not be fully typed in a way that satisfies the stricter checks introduced in newer versions of @typescript-eslint/eslint-plugin. This can happen when Vite's internal types or the types exposed by the React plugin don't precisely match what ESLint expects, causing it to flag the call as potentially unsafe. Addressing this typically involves ensuring all related packages are updated to compatible versions, or adjusting ESLint rules to accommodate the discrepancies while still maintaining a high level of type safety. Identifying the precise combination of package versions that trigger the error is a key step in finding a stable and reliable solution.

Reproduction Steps

So, how can you see this in action? It's pretty straightforward. First, you need a vite.config.ts file that includes the standard react() setup. You'll also need @typescript-eslint/eslint-plugin installed for ESLint. A minimal setup might look something like this:

// vite.config.ts
import { defineConfig } from 'vite';
import react from '@vitejs/plugin-react';

export default defineConfig({
 plugins: [
 react(), // This is where the error often occurs
 ],
});

Then, run ESLint on your configuration file. If you're encountering the bug, you should see the Unsafe call of a(n) 'error' type typed value error pointing to the react() line. A really handy way to reproduce this consistently is by using a tool like StackBlitz. There's even a reproduction available here: https://stackblitz.com/edit/vitejs-vite-s2jvgte3?file=eslint.config.ts. This StackBlitz setup makes it super easy to see the issue in real-time and experiment with potential fixes.

Key Steps to Reproduce:

  1. Set up a new Vite project with TypeScript.
  2. Install @vitejs/plugin-react and @typescript-eslint/eslint-plugin.
  3. Create a vite.config.ts file and include the react() plugin.
  4. Run ESLint on the configuration file.

If the versions of your packages align to trigger the bug, ESLint will flag the react() call as unsafe, highlighting the type mismatch that's causing the issue. This simple reproduction allows developers to quickly confirm whether they are facing the same problem and start exploring solutions. The key is to have a consistent environment where the issue can be reliably reproduced, making it easier to test potential fixes and ensure they address the underlying problem.

Diving Deeper: System Info and Package Managers

To really get to the bottom of this, it's crucial to look at your system setup and the tools you're using. The original bug report provides some fantastic system info, which is super helpful for diagnosing issues like this. Let's break it down:

System:
 OS: Linux 6.1 Debian GNU/Linux trixie/sid
 CPU: (12) x64 Intel(R) Core(TM) i7-10750H CPU @ 2.60GHz
 Memory: 21.48 GB / 31.10 GB
 Container: Yes
 Shell: 5.7.1 - /usr/bin/zsh
Binaries:
 Node: 22.18.0 - ~/.asdf/installs/nodejs/22.18.0/bin/node
 npm: 10.9.3 - ~/.asdf/installs/nodejs/22.18.0/bin/npm
 pnpm: 10.14.0 - ~/.asdf/shims/pnpm
Browsers:
 Chromium: 138.0.7204.92
npmPackages:
 @vitejs/plugin-react: ^5.0.0 => 5.0.0
 vite: ^7.0.0 => 7.1.1

This tells us a lot! We see the OS, CPU, memory, shell, Node.js version, and importantly, the versions of @vitejs/plugin-react and vite. Knowing these versions helps us narrow down if specific versions are more prone to the issue. Additionally, the user is using pnpm as their package manager, which can sometimes behave differently than npm or yarn. The key here is to understand that discrepancies in package versions and package manager behaviors can often lead to unexpected issues, especially when dealing with complex build tools like Vite and ESLint. Having this detailed system information allows us to more effectively pinpoint the source of the problem and work towards a solution that fits the specific environment.

Package Managers Matter

Speaking of package managers, it's worth noting that pnpm, npm, and yarn handle dependencies in slightly different ways. pnpm, for example, uses a more efficient approach with symlinks, which can sometimes lead to different outcomes compared to npm or yarn when resolving dependencies. This difference in dependency resolution can occasionally surface issues that are specific to one package manager but not others. So, if you're encountering a bug, it's always a good idea to check if the same issue occurs with a different package manager. This can help you isolate whether the problem is with your configuration or with the way a particular package manager is handling your project's dependencies. Keeping these nuances in mind is crucial for effective troubleshooting and ensuring a consistent development environment across different systems.

Potential Solutions and Workarounds

Alright, let's get to the juicy part: how do we actually fix this thing? There are a few avenues we can explore, and the best approach might depend on your specific setup and constraints.

1. Version Alignment

The first thing you should always check is your package versions. Make sure that your @vitejs/plugin-react, vite, @typescript-eslint/eslint-plugin, and related packages are all compatible with each other. Sometimes, a simple update or downgrade can resolve these kinds of issues. For instance, you might try updating @vitejs/plugin-react and vite to the latest versions, or if you recently updated, you could try rolling back to the previous versions that were working for you. Version mismatches are a common cause of these ESLint errors, so this is often the first and easiest fix to try. Always consult the documentation for each package to understand their compatibility requirements and ensure you're using a combination that is known to work well together.

2. ESLint Configuration Adjustments

Sometimes, the issue isn't a bug per se, but rather a configuration issue with ESLint. The @typescript-eslint/no-unsafe-call rule is designed to catch potentially unsafe function calls, but it can sometimes be a bit too aggressive. You might consider adjusting your ESLint configuration to either disable the rule entirely (not recommended as a long-term solution) or configure it to be less strict for specific cases. For example, you could disable the rule for the react() call specifically, like so:

// .eslintrc.js
module.exports = {
 rules: {
 '@typescript-eslint/no-unsafe-call': [
 'warn',
 { ignoreCalls: ['react'] },
 ],
 },
};

This tells ESLint to only warn about unsafe calls to react() rather than throwing an error. While this can be a quick fix, it's crucial to understand the implications of disabling or modifying ESLint rules. Make sure you're not inadvertently silencing a real issue that could lead to runtime problems. It's generally better to find a more targeted solution that addresses the underlying type mismatch, but this can be a useful workaround in the short term.

3. Type Definitions

In some cases, the type definitions for @vitejs/plugin-react might not be fully aligned with the expectations of @typescript-eslint/eslint-plugin. This can happen if there are discrepancies in how the types are defined or if certain type annotations are missing. One potential workaround is to manually provide more specific type annotations to help ESLint understand the context of the react() call. This might involve casting the result of react() to a specific type or providing additional type information in your vite.config.ts file. However, this approach requires a solid understanding of TypeScript's type system and the specific types involved. It's also important to ensure that any manual type annotations are accurate and don't introduce new type errors or mask underlying issues. If you're comfortable working with TypeScript types, this can be a powerful way to resolve the issue, but it should be approached with caution.

4. Reporting the Issue

If you've tried the above steps and you're still running into the error, it's a great idea to report the issue to the Vite team or the @typescript-eslint/eslint-plugin maintainers. Providing a clear and detailed bug report, along with a minimal reproduction (like the StackBlitz example mentioned earlier), can help them identify the root cause and develop a proper fix. When reporting the issue, be sure to include your system information, package versions, and any relevant error messages or logs. The more information you can provide, the easier it will be for the maintainers to understand and address the problem. Reporting issues helps the entire community and ensures that these tools continue to improve and become more reliable.

Validations and Best Practices

Before we wrap up, let's touch on some important validations and best practices. The original bug report includes a checklist of validations that are worth highlighting:

These are all excellent practices to follow when encountering and reporting bugs. Make sure you've done your homework before submitting an issue, and always provide a minimal reproduction to help the maintainers understand the problem. It's also crucial to ensure that the issue is indeed a bug and not a configuration error or misunderstanding. Following these guidelines ensures that your bug reports are clear, actionable, and contribute to the overall quality of the project.

Wrapping Up

So, there you have it! The Unsafe call error in Vite 5.0 with TypeScript and ESLint can be a bit of a head-scratcher, but by understanding the potential causes and following the troubleshooting steps outlined above, you should be well-equipped to tackle it. Remember to check your package versions, adjust your ESLint configuration if needed, consider providing manual type annotations, and don't hesitate to report the issue if you're still stuck. Happy coding, folks!