Support ESLint 9

[fisker]

ESLint v9.0.0-alpha.0 released

[JoshuaKGoldberg]

🤔 #186 mostly just has test file changes. Does that imply eslint-utils already supports ESLint 9?

cc @voxpelli from eslint/eslint#18093 (comment)

[fisker]

No, can't be installed without --legacy-peer-deps, it's blocking unicorn https://github.com/sindresorhus/eslint-plugin-unicorn/actions/runs/8019879716/job/21908544750?pr=2250#step:4:14

[voxpelli]

No, can't be installed without --legacy-peer-deps, it's blocking unicorn

I guess that's because >=8.0.0 doesn't match prereleases, which makes little sense for peer dependencies, but since it's easier to change here than to change npm I guess we could update it to say:

^8.0.0 || >=9.0.0-beta.2

That should fix it, right?

[voxpelli]

One thing I don't get about version ranges and npm is that when I try it on https://semver.npmjs.com/ I get this:

>=9.0.0-0: 9.0.0-alpha.0, 9.0.0-alpha.1, 9.0.0-alpha.2, 9.0.0-beta.0, 9.0.0-beta.1, 9.0.0-beta.2
^8.0.0 || >=9.0.0-0: no 9.x versions at all 🤔

I wonder if that's a bug with semver.npmjs.com or with semver in itself – I will investigate.

---

This is a similar issue as in eslint-community/eslint-plugin-n#197 – that >=8.0.0 doesn't include prereleases of new versions is quite a challenge. Might be that we should always do the >= on the earliest next major version pre-release rather than on the current stable major release

[voxpelli]

I tested using the semver module itself:

import { satisfies, compare } from 'semver';

console.log(satisfies('8.2.3',         '^8.0.0 || >=9.0.0-0')); // true
console.log(satisfies('9.0.0-beta.2',  '^8.0.0 || >=9.0.0-0')); // true
console.log(satisfies('9.2.3',         '^8.0.0 || >=9.0.0-0')); // true
console.log(satisfies('9.2.3-beta.2',  '^8.0.0 || >=9.0.0-0')); // false
console.log(satisfies('10.0.0-beta.2', '^8.0.0 || >=9.0.0-0')); // false
console.log(satisfies('10.0.0',        '^8.0.0 || >=9.0.0-0')); // true

console.log('');

console.log(satisfies('9.0.0-beta.2',  '>=8.0.0', { includePrerelease: true })); // true
console.log(satisfies('9.2.3-beta.2',  '>=8.0.0', { includePrerelease: true })); // true
console.log(satisfies('10.0.0-beta.2', '>=8.0.0', { includePrerelease: true })); // true

// [ '9.0.0-0', '9.0.0--', '9.0.0-a', '9.0.0-beta.2' ]
console.log(['9.0.0--', '9.0.0-0', '9.0.0-a', '9.0.0-beta.2'].sort(compare));

This shows:

• ^8.0.0 || >=9.0.0-0 will work for all pre-releases of 9.0.0 + all stable versions of 9.x
• ^8.0.0 || >=9.0.0-0 will not work for any pre-releases of versions later than 9.0.0 – eg. neither 9.2.3-beta.2 nor '10.0.0-beta.2'
• x.y.z-0 is the earliest possible pre-release of any version, so setting that as the lower limit is the same as saying "all pre-releases"

I'll open a PR

[voxpelli]

Found a relevant RFC: npm/rfcs#397

[harryzcy]

It looks like ESLint 9 is released, so matching pre-releases is no longer necessary.

[barbalex]

It seems it does not work though?
I am using:

"eslint": "9.0.0",

And getting:

√ Run npm install to install new versions? ... yes
Installing dependencies...
npm ERR! 
code ERESOLVE

npm ERR!
 ERESOLVE could not resolve
npm ERR! 
npm ERR! While resolving: @typescript-eslint/[email protected]
npm ERR! Found: [email protected]
npm ERR! node_modules/eslint
npm ERR!   dev eslint@"9.0.0" from the root project
npm ERR!   peer eslint@"^6.0.0 || ^7.0.0 || >=8.0.0" from @eslint-community/[email protected]
npm ERR!   node_modules/@eslint-community/eslint-utils
npm ERR!     @eslint-community/eslint-utils@"^4.4.0" from @typescript-eslint/[email protected]
npm ERR!     node_modules/@typescript-eslint/eslint-plugin/node_modules/@typescript-eslint/utils
npm ERR!       @typescript-eslint/utils@"7.5.0" from @typescript-eslint/[email protected]
npm ERR!       node_modules/@typescript-eslint/eslint-plugin
npm ERR!         dev @typescript-eslint/eslint-plugin@"7.5.0" from the root project
npm
ERR!       1 more (@typescript-eslint/type-utils)
npm ERR!     @eslint-community/eslint-utils@"^4.2.0" from [email protected]
npm ERR!   1 more (eslint-plugin-react-refresh)
npm ERR!
npm ERR! Could not resolve dependency:
npm ERR! peer eslint@"^8.56.0" from @typescript-eslint/[email protected]
npm ERR! node_modules/@typescript-eslint/eslint-plugin
npm ERR!   dev @typescript-eslint/eslint-plugin@"7.5.0" from the root project
npm ERR!
npm ERR! Conflicting peer dependency: [email protected]
npm ERR! node_modules/eslint
npm ERR!   peer eslint@"^8.56.0" from @typescript-eslint/[email protected]
npm ERR!   node_modules/@typescript-eslint/eslint-plugin
npm ERR!     dev @typescript-eslint/eslint-plugin@"7.5.0" from the root project
npm ERR!
npm ERR! Fix the upstream dependency conflict, or retry
npm ERR! this command with --force or --legacy-peer-deps
npm ERR! to accept an incorrect (and potentially broken) dependency resolution.
npm ERR!
npm ERR!
npm ERR! For a full report see:
npm ERR! C:\Users\alexa\AppData\Local\npm-cache\_logs\2024-04-07T08_45_30_389Z-eresolve-report.txt


npm ERR! A complete log of this run can be found in: C:\Users\alexa\AppData\Local\npm-cache\_logs\2024-04-07T08_45_30_389Z-debug-0.log

Error: npm ERR! code ERESOLVE
npm ERR! ERESOLVE could not resolve
npm ERR!
npm ERR! While resolving: @typescript-eslint/[email protected]
npm ERR! Found: [email protected]
npm ERR! node_modules/eslint
npm ERR!   dev eslint@"9.0.0" from the root project
npm ERR!   peer eslint@"^6.0.0 || ^7.0.0 || >=8.0.0" from @eslint-community/[email protected]
npm ERR!   node_modules/@eslint-community/eslint-utils
npm ERR!     @eslint-community/eslint-utils@"^4.4.0" from @typescript-eslint/[email protected]
npm ERR!     node_modules/@typescript-eslint/eslint-plugin/node_modules/@typescript-eslint/utils
npm ERR!       @typescript-eslint/utils@"7.5.0" from @typescript-eslint/[email protected]
npm ERR!       node_modules/@typescript-eslint/eslint-plugin
npm ERR!         dev @typescript-eslint/eslint-plugin@"7.5.0" from the root project
npm ERR!       1 more (@typescript-eslint/type-utils)
npm ERR!     @eslint-community/eslint-utils@"^4.2.0" from [email protected]
npm ERR!   1 more (eslint-plugin-react-refresh)
npm ERR!
npm ERR! Could not resolve dependency:
npm ERR! peer eslint@"^8.56.0" from @typescript-eslint/[email protected]
npm ERR! node_modules/@typescript-eslint/eslint-plugin
npm ERR!   dev @typescript-eslint/eslint-plugin@"7.5.0" from the root project
npm ERR!
npm ERR! Conflicting peer dependency: [email protected]
npm ERR! node_modules/eslint
npm ERR!   peer eslint@"^8.56.0" from @typescript-eslint/[email protected]
npm ERR!   node_modules/@typescript-eslint/eslint-plugin
npm ERR!     dev @typescript-eslint/eslint-plugin@"7.5.0" from the root project
npm ERR!
npm ERR! Fix the upstream dependency conflict, or retry
npm ERR! this command with --force or --legacy-peer-deps
npm ERR! to accept an incorrect (and potentially broken) dependency resolution.
npm ERR!
npm ERR!
npm ERR! For a full report see:
npm ERR! C:\Users\alexa\AppData\Local\npm-cache\_logs\2024-04-07T08_45_30_389Z-eresolve-report.txt

npm ERR! A complete log of this run can be found in: C:\Users\alexa\AppData\Local\npm-cache\_logs\2024-04-07T08_45_30_389Z-debug-0.log

    at C:\Users\alexa\AppData\Roaming\nvm\v21.1.0\node_modules\npm-check-updates\build\src\index.js:178:23
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)

[voxpelli]

@barbalex I believe that error is caused by @typescript-eslint/eslint-plugin not allowing eslint 9

[JoshuaKGoldberg]

For reference: typescript-eslint/typescript-eslint#8211

We're a little behind over on typescript-eslint but we're working on it. Hoping to get the support out soon. ❤️