fix: update @eslint/core to v1.0.0 and adjust tests

[lumirlumir]

Prerequisites checklist

• I have read the contributing guidelines.

What is the purpose of this pull request?

This PR was motivated by #187 (comment).

Currently, when updating @eslint/core to v1.0.0, CI fails because @eslint/core@1.0.0 does not match ESLint v9

@eslint/core@1.0.0 includes type information for ESLint v10, which causes the type mismatch.

So, I've updated ESLint to >=10.0.0-alpha.0 <10.0.0 || ^10.0.1. (Ref: https://github.com/eslint/eslint/blob/main/packages/eslint-config-eslint/package.json#L66)

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When I update ESLint to >=10.0.0-alpha.0 <10.0.0 || ^10.0.1, the following error occurs, so I added the legacy-peer-deps option to .npmrc.

This change follows the approach in eslint/eslint#20281

What changes did you make? (Give an overview)

In this PR, I've updated @eslint/core, add legacy-peer-deps, and use ESLint v10 pre-release.

Related Issues

Ref: #187, #187 (comment), eslint/eslint#20281

Is there anything you'd like reviewers to focus on?

N/A

[eslint-github-bot]

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[eslint-github-bot]

Hi @lumirlumir!, thanks for the Pull Request

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[lumirlumir]

From ESLint v10, errors property in valid test case throws error, so I've removed it.

Ref: https://eslint.org/docs/next/use/migrate-to-10.0.0#stricter-rule-tester

[lumirlumir]

Counterpart PR in eslint/css: eslint/css#337

[mdjermanovic]

Since this is a dependency, will this affect end users who are still using ESLint v9?

[nzakas]

The next release will be a major one, so I think it's okay.

[nzakas]

I'm wondering -- can we just update the types test to use Plugin from @eslint/core instead of ESLint.Plugin?

[nzakas]

The next release will be a major one, so I think it's okay.

[lumirlumir]

When I look at the history of the ESLint.plugin test, it appears it was added primarily to ensure compatibility with the ESLint.plugin type before the @eslint/core package was stabilized.

Below is the git blame for the related PRs in chronological order:

• 2024-11-22: https://github.com/eslint/json/pull/65/files
• 2025-02-06: https://github.com/eslint/json/pull/66/files
• 2025-03-23: https://github.com/eslint/json/pull/89/files

Personally, I think it would be fine to replace the ESLint.plugin type from eslint with the Plugin type from @eslint/core, since ESLint.plugin is identical to the Plugin type in both v9 and v10.

Would anyone from @eslint/eslint-tsc have any further thoughts on this?

[fasttime]

When I look at the history of the ESLint.plugin test, it appears it was added primarily to ensure compatibility with the ESLint.plugin type before the @eslint/core package was stabilized.

Yes, the Plugin type in @eslint/core was added recently, in v0.16.0 (eslint/rewrite#237).

Personally, I think it would be fine to replace the ESLint.plugin type from eslint with the Plugin type from @eslint/core, since ESLint.plugin is identical to the Plugin type in both v9 and v10.

Would anyone from @eslint/eslint-tsc have any further thoughts on this?

I think that's fine.

[lumirlumir]

Per the suggestions, I've updated types.test.ts to use the Plugin type instead of ESLint.Plugin in d7d3b71

[Copilot]

Pull request overview

This PR updates the repository to work with ESLint v10 pre-release versions and @eslint/core v1.0.0, addressing type compatibility issues between these packages. The changes align with the pattern established in eslint/eslint#20281 for adopting ESLint v10 pre-releases.

• Updated @eslint/core from ^0.17.0 to ^1.0.0 to include ESLint v10 type information
• Added legacy-peer-deps = true to .npmrc to bypass peer dependency conflicts during the pre-release period
• Updated ESLint dependency to use the version range >=10.0.0-alpha.0 <10.0.0 || ^10.0.1 to support v10 pre-releases

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
package.json	Updated @eslint/core to v1.0.0 and ESLint to v10 pre-release version range
.npmrc	Added legacy-peer-deps flag with TODO comment for removal after ESLint v10 stable release
tests/types/types.test.ts	Updated type imports to use Plugin from @eslint/core instead of ESLint.Plugin
tests/rules/sort-keys.test.js	Removed erroneous errors array from valid test case (fix for ESLint v10 compatibility)

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[nzakas]

Do we still need legacy-peer-deps?

[lumirlumir]

I think it's still needed, since sub-dependencies of the eslint-config-eslint package, such as eslint-plugin-jsdoc, still require ^7.0.0 || ^8.0.0 || ^9.0.0 rather than v10.

json/package.json

Line 95 in a0c552d

"eslint-config-eslint": "^13.0.0",

https://github.com/gajus/eslint-plugin-jsdoc/blob/3cd7cbddecf01b59c07c8fba850da24228cb50ef/package.json#L149-L151

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When I run npm install without legacy-peer-deps, I get the following errors:

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Per the comments above and the discussion at eslint/js#709 (comment), I added a commit 466cdc6 to clarify the description in .npmrc and to set the eslint version to >=10.0.0-alpha.0 <10.0.0 || ^10.0.0.

[nzakas]

Right, but if we keep this using ESLint v9 for linting, then I don't think we need legacy-peer-deps. There doesn't appear to be any reason to have a direct dependency on ESLint v10?

[lumirlumir]

Right, but if we keep this using ESLint v9 for linting, then I don't think we need legacy-peer-deps. There doesn't appear to be any reason to have a direct dependency on ESLint v10?

I have missed that it switched to the Plugin type instead of ESLint.Plugin in #190 (comment). I'll revert the PR to use ESLint v9 and remove legacy-peer-deps.

Also, I've marked the PR prefix as fix since it updates dependencies, as discussed in eslint/workflows#33 (comment).

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I've reverted the changes in 1cb0fa8.

[lumirlumir]

Question:

Would there be a plan to remove rollup and migrate to an ESM-only package for the upcoming v1.0.0 stable release?

I opened an issue with more details: #196

[nzakas]

LGTM. Would like @mdjermanovic to review before merging.

[mdjermanovic]

LGTM, thanks!