Add ESLint 9 to support oxlint

[uday-rana]

Fixes #803

Changes

• Added ESLint 9, which is to be run after oxlint as a fallback for linting rules that aren't covered by oxlint. Rules that oxlint does cover won't be linted again by ESLint. This is the approach recommended by oxc:

  We recommend running oxlint before ESLint in your lint-staged or CI setup for a quicker feedback loop, considering it only takes a few seconds to run on large codebases.

  • I created the config file by grabbing the ESLint 8 flat config template recommended by Remix and using ESLint's config migrator on it. I then tweaked it from there.

• Added two oxc plugins not enabled by default: jsx-a11y and import

  • These plugins don't implement all of the linting rules of their ESLint equivalents, so we need to keep the ESLint plugins too. See Consider oxlint as replacement of eslint cockpit-project/cockpit#20279

• Removed some settings from .oxlintrc.json that didn't do anything or were just re-defining the defaults.

• Fixed lint errors detected after ESLint was added.

[uday-rana]

When saving a file, the VSCode ESLint extension removes eslint-disable comments for rules that are overridden by oxlint, making it impossible to disable rules for oxlint when using the ESLint extension. Need to find a fix.

[uday-rana]

When saving a file, the VSCode ESLint extension removes eslint-disable comments for rules that are overridden by oxlint, making it impossible to disable rules for oxlint when using the ESLint extension. Need to find a fix.

Set ESLint up to ignore unused disable directives.

[theoforger]

@uday-rana Great job 👍. Since ESLint 9 dropped support for .eslintignore file, I wonder if it's still possible to have a single source for ignored files?

[uday-rana]

@uday-rana Great job 👍. Since ESLint 9 dropped support for .eslintignore file, I wonder if it's still possible to have a single source for ignored files?

We can import the ignore list from gitignore into eslint: https://eslint.org/docs/latest/use/configure/ignore#including-gitignore-files

[theoforger]

@uday-rana There's also a command line option --ignore-path form oxlint. Although it's not available as an config file option, we can include it in the npm script. What do you think?

To avoid confusion maybe we can include a comment in .oxlintrc.json explaining this situation

[uday-rana]

@uday-rana There's also a command line option --ignore-path form oxlint. Although it's not available as an config file option, we can include it in the npm script. What do you think?

To avoid confusion maybe we can include a comment in .oxlintrc.json explaining this situation

That could lead to inconsistent behaviour if oxlint is run with npx vs through the npm script. If it's not supported in the config file we could just keep things simple for now. We also don't know if using --ignore-path to point to .gitignore will let us keep overrides in the config file for directories we want in Git but don't want to format.

[theoforger]

@uday-rana Makes sense! Let's stick with what we have so far.