Use language config in shareable configs

[Copilot]

✅ Use language config in shareable configs - COMPLETE

This is a breaking change to use the new ESLint v9 language config API instead of the legacy parser approach.

Changes Made:

• Explore repository structure and understand the issue
• Understand current sharable configs implementation
• Understand language config API (YAMLLanguage class)
• Run baseline tests - all passing (5481 tests)
• Update base.ts config to use language config instead of parser
• Run tests to verify changes work correctly (5481 tests still passing)
• Create changeset file for breaking change
• Final validation with code review and security scan
• Add test to verify language config is used instead of parser
• Improve test pattern matching for robustness
• Fix linting errors

Summary:

The shareable configs (base, recommended, standard, prettier) now use the new ESLint v9 language config API (language: "yml/yaml") instead of the legacy parser approach (languageOptions: { parser: yaml-eslint-parser }).

Breaking Change: Users of the shareable configs will now automatically get the language config applied.

All tests passing: 5484 tests ✓ (3 new tests added)
No security vulnerabilities: CodeQL scan clean ✓
Code review: All issues addressed ✓
Linting: All errors fixed ✓

Original prompt

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This section details on the original issue you should resolve

<issue_title>Using language config in sharable configs</issue_title>
<issue_description>I noticed that the sharable configs provided by this plugin don't use the newly added language config 😓

The plugin needs to use the language config in the sharable configs, but this is a breaking change.</issue_description>

<agent_instructions>Add a changeset file at the end of the work</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Using language config in sharable configs #542

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[changeset-bot]

🦋 Changeset detected

Latest commit: 8281772

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

This PR includes changesets to release 1 package

Name	Type
eslint-plugin-yml	Major

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[Copilot]

Pull request overview

This PR migrates the shareable configs from the legacy parser approach to ESLint v9's language config API, using language: "yml/yaml" instead of languageOptions: { parser: yaml-eslint-parser }.

Changes:

• Updated base config to use language config API
• Added comprehensive tests to verify the language config is correctly applied
• Added changeset documenting this as a breaking change

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
src/configs/flat/base.ts	Removed parser import and languageOptions, added language config field
tests/src/configs/base.ts	Added new test suite to verify language config usage and backward compatibility
.changeset/language-config-in-shareable-configs.md	Added changeset documenting the breaking change with major version bump

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[ota-meshi]

Please fix linting errors

[Copilot]

Please fix linting errors

Fixed linting errors in commit 8281772. Applied prettier formatting to the test file.

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