Tim Addison

Updating babel-eslint to @babel/eslint-parser for React apps

As of March 2020, babel-eslint has been deprecated, and is now @babel/eslint-parser. That doesn’t stop it (as of March 2021) being downloaded 6.5 million times per week. You wouldn’t know this unless you attempted to add it as a new dependency, in which case npm would tell you:

npm WARN deprecated babel-eslint@10.1.0: babel-eslint is now @babel/eslint-parser. This package will no longer receive updates.

Upgrading is straightforward but I couldn’t find any clear guides - so if you want to avoid the trial and error you can follow the below steps (which I’ve tested on Create React App, Next.js, and Vite apps - which all use Babel under the hood).

As to why babel-eslint has been deprecated? It’s documented in the (now archived) babel-eslint repo:

As of the v11.x.x release, babel-eslint now requires Babel as a peer dependency and expects a valid Babel configuration file to exist. This ensures that the same Babel configuration is used during both linting and compilation.

Short version

  • Remove babel-eslint
  • Add @babel/eslint-parser @babel/preset-react
    • You may also need the peer dependency @babel/core (npm7 installs peer dependencies by default)
  • Update the parser in your .eslintrc.* file (from babel-eslint to @babel/eslint-parser)
  • Add the following to the parserOptions configuration in your .eslintrc.* file:
requireConfigFile: false,
babelOptions: {
  presets: ["@babel/preset-react"]
}

Longer version

First, switch out the Babel eslint plugin by removing babel-eslint and installing @babel/eslint-parser:

npm uninstall babel-eslint
npm install @babel/eslint-parser -D

If you’re not running npm 7 (Node15) you will also need to add @babel/core, which is a peer dependency of @babel/eslint-parser. From npm 7 peer dependencies are installed by default.

And then update the parser (in your .eslintrc.* file):

- parser: 'babel-eslint',
+ parser: '@babel/eslint-parser',

If you run eslint now you’ll now get an error about config files:

 0:0  error  Parsing error: No Babel config file detected for C:\temp\site-test\tailwind.config.js. Either disable config file checking with requireConfigFile: false, or configure Babel so that it can find the config files

To fix this we need to modify parserOptions:

+  parserOptions: {
+    requireConfigFile: false,
+  },

And now if we run eslint again? An error parsing React code (specifically jsx), which helpfully tells us how to fix the issue:

 18:4  error  Parsing error: C:\temp\site-test\src\templates\blog-post.js: Support for the experimental syntax 'jsx' isn't currently enabled (18:5):
  16 |
  17 |   return (
> 18 |     <Layout>
     |     ^

Add @babel/preset-react (https://git.io/JfeDR) to the 'presets' section of your Babel config to enable transformation.
If you want to leave it as-is, add @babel/plugin-syntax-jsx (https://git.io/vb4yA) to the 'plugins' section to enable parsing

So let’s install the plugin:

npm install @babel/preset-react -D

And then update our parserOptions to pass this option through to Babel:

parserOptions: {
  requireConfigFile: false,
+  babelOptions: {
+    presets: ["@babel/preset-react"],
+  },
},

And we’ll finally be able to run eslint!