1881702 - Switch to ESLint v9.6.0

Status: RESOLVED FIXED

(Developer Infrastructure :: Lint and Formatting, task, P3)

Description

[Mark Banner (:standard8)]

Once we've migrated to flat config (bug 1881701), we should upgrade to ESLint v9 itself.

Comment 1

[Mark Banner (:standard8)]

I'm starting off with a small bump to ESLint 9.6.0 to avoid having to get us onto the 9.x series. There's more issues to resolve if we go all the way to 9.27.0 in one jump, though I've not looked into how much work they'll take to resolve. So what I'd like to do is get to 9.6.0, clean up eslint-plugin-mozilla (to remove all the pre-v9 support code), and then investigate updating to the latest. This will also help with more investigation of new features along the way.

For the 9.6.0 jump, the release notes can be found here:

• https://eslint.org/blog/2024/04/eslint-v9.0.0-released/
• https://eslint.org/blog/2024/04/eslint-v9.1.0-released/
• https://eslint.org/blog/2024/05/eslint-v9.2.0-released/
• https://eslint.org/blog/2024/05/eslint-v9.3.0-released/
• https://eslint.org/blog/2024/05/eslint-v9.4.0-released/
• https://eslint.org/blog/2024/06/eslint-v9.5.0-released/
• https://eslint.org/blog/2024/06/eslint-v9.6.0-released/

I think the main highlights are:

• valid-jsdoc and require-jsdoc rules have been removed (not to be confused with the valid-jsdoc and require-jsdoc configurations that we have in eslint-plugin-mozilla)
• The complexity rule now also takes into account optional chaining and default values in destructuring patterns and parameters (which generally means higher complexity scores).
• The no-unused-vars rule has a new default value for the caughtErrors option (changed from "none" to "all")
  • For now, I'm turning this off again, but we might want to consider enabling it in the future.
• reportUnusedDisableDirectives is on by default, but I'm turning it off in our configuration, will comment in bug 1904558 about the reasons.
• Intl is now recognized as a built-in global
• The no-constant-condition rule no longer reports while (true) loops as problems by default (xref)

Comment 2

[Mark Banner (:standard8)]

Attachment: Bug 1881702 - Remove references to ESLint rule valid-jsdoc which was removed in v9. r?#frontend-codestyle-reviewers!

Comment 3

[Mark Banner (:standard8)]

Attachment: Bug 1881702 - Update eslint-plugin-mozilla tests to work with ESLint v9. r?#frontend-codestyle-reviewers!

Comment 4

[Mark Banner (:standard8)]

Attachment: Bug 1881702 - Upgrade ESLint versions to v9.6.0. r?#frontend-codestyle-reviewers!

Comment 5

[Mark Banner (:standard8)]

Attachment: Bug 1881702 - Turn off caughtErrors on ESLint rule no-unused-vars for the time being. r?#frontend-codestyle-reviewers!

Comment 6

[Mark Banner (:standard8)]

Attachment: Bug 1881702 - Fix no-unused-vars issues raised by the upgrade to ESLint v9. r?#frontend-codestyle-reviewers!

This disables caughtErrors from everywhere. This is enabled by default in v9. We should work to enable this later.
This also changes the exported comments - ESLint is more strict about what it can handle, and doesn't like a star
in the middle of the comment.
Also tidies up some rules where they are no longer needed.

Comment 7

[Mark Banner (:standard8)]

Attachment: Bug 1881702 - Fix ESLint complexity issues raised after upgrading to v9. r?#frontend-codestyle-reviewers!

Comment 8

[Mark Banner (:standard8)]

Attachment: Bug 1881702 - Use import.meta.dirname for the current dirname for the top-level eslint.config.mjs, now that node has been upgraded. r?#frontend-codestyle-reviewers!

Comment 9

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/1b43d3819198
Remove references to ESLint rule valid-jsdoc which was removed in v9. r=frontend-codestyle-reviewers,extension-reviewers,search-reviewers,omc-reviewers,android-reviewers,webcompat-reviewers,willdurand,mossop,daleharvey,twisniewski,nalexander,emcminn
https://hg.mozilla.org/integration/autoland/rev/5c4751bb8409
Update eslint-plugin-mozilla tests to work with ESLint v9. r=frontend-codestyle-reviewers,mossop
https://hg.mozilla.org/integration/autoland/rev/7112920935a5
Upgrade ESLint versions to v9.6.0. r=frontend-codestyle-reviewers,home-newtab-reviewers,mossop,maxx
https://hg.mozilla.org/integration/autoland/rev/418f8176bc99
Fix no-unused-vars issues raised by the upgrade to ESLint v9. r=frontend-codestyle-reviewers,perftest-reviewers,geckoview-reviewers,extension-reviewers,devtools-reviewers,migration-reviewers,android-reviewers,webcompat-reviewers,nchevobbe,mossop,sparky,twisniewski,ohall
https://hg.mozilla.org/integration/autoland/rev/3cc848387b54
Fix ESLint complexity issues raised after upgrading to v9. r=frontend-codestyle-reviewers,extension-reviewers,devtools-reviewers,anti-tracking-reviewers,tabbrowser-reviewers,omc-reviewers,nchevobbe,timhuang,mossop,nsharpley,emcminn
https://hg.mozilla.org/integration/autoland/rev/964aadc52be9
Use import.meta.dirname for the current dirname for the top-level eslint.config.mjs, now that node has been upgraded. r=frontend-codestyle-reviewers,mossop

Comment 10

[amarc]

https://hg.mozilla.org/mozilla-central/rev/1b43d3819198
https://hg.mozilla.org/mozilla-central/rev/5c4751bb8409
https://hg.mozilla.org/mozilla-central/rev/7112920935a5
https://hg.mozilla.org/mozilla-central/rev/418f8176bc99
https://hg.mozilla.org/mozilla-central/rev/3cc848387b54
https://hg.mozilla.org/mozilla-central/rev/964aadc52be9