feat: upgrade eslint in create-svelte to v9

[jrmajor]

Upgrades ESLint in create-svelte to v9 and migrates config from .eslintrc.cjs and .eslintignore to eslint.config.js.

Closes #10742.

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🦋 Changeset detected

Latest commit: bb12553

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
create-svelte	Minor

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[jrmajor]

Blocked by sveltejs/eslint-plugin-svelte#727.

[jrmajor]

Not sure what build and package directories are used for, but they were in the .eslintignore.

ESLint doesn't seem to care about .DS_Store, .env*, pnpm-lock.yaml, package-lock.json or yarn.lock, so I didn't add them.

I've also skipped node_modules, since it's ignored by default.

[eltigerchino]

I believe build is the output directory for adapter-static, etc. and package is the directory when packaging the lib directory with @sveltejs/package? (not sure myself)

[jrmajor]

I believe build is the output directory for adapter-static, etc.

I think that's correct, found this in docs: https://kit.svelte.dev/docs/adapter-static#options-pages.

package is the directory when packaging the lib directory with @sveltejs/package? (not sure myself)

I've created a new library using yarn create svelte and ran yarn run package. It created a dist directory, so package must be for something else.

[jprinaldi]

I believe that's the case, yeah. And regarding some of the other files, it seems they are leftovers from the time they decided to stop using .gitignore as the ignore file for eslint and prettier.

I believe build is the output directory for adapter-static, etc. and package is the directory when packaging the lib directory with @sveltejs/package? (not sure myself)

[dominikg]

@ota-meshi do we have to update the combined eslint + prettier template to add the ruleset that disables some rules to avoid prettier conflicts?

[jrmajor]

do we have to update the combined eslint + prettier template to add the ruleset that disables some rules to avoid prettier conflicts?

@dominikg I think that's what https://github.com/prettier/eslint-config-prettier is supposed to do.

[dominikg]

i mean https://github.com/sveltejs/eslint-plugin-svelte?tab=readme-ov-file#new-config-eslintconfigjs

specifically eslintPluginSvelte.configs['flat/prettier'] in case a user selects both prettier and eslint in the shell dialogue started with create-svelte both prettier and eslint configs should be set up in a way that they work well together. This is achieved by the different + / - templates. the one that is for prettier+eslint might need to include this config to ensure that the two don't collide. prettier-plugin-svelte alone can't do it as it doesn't have access to eslint config

[jrmajor]

@dominikg You're right, should be fixed now. Strange that it wasn't there before, since it was introduced way back in https://github.com/sveltejs/eslint-plugin-svelte/releases/tag/v2.2.0.