feat(rule-tester): port checkDuplicateTestCases from ESLint

[abrahamguo]

PR Checklist

• Addresses an existing open issue: fixes Enhancement(rule-tester): detect duplicate test cases #9018
• That issue was marked as accepting prs
• Steps in Contributing were taken

Overview

Ports checkDuplicateTestCases from ESLint's RuleTester.

[typescript-eslint]

Thanks for the PR, @abrahamguo!

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The core maintainers work on this in their personal time, so please understand that it may not be possible for them to review your work immediately.

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✅ Successfully ran 31 targets

• nx test eslint-plugin --coverage=false
• nx test eslint-plugin
• nx test typescript-estree --coverage=false
• nx test type-utils --coverage=false
• nx test utils --coverage=false
• nx run types:build
• nx test repo-tools --coverage=false
• nx test visitor-keys --coverage=false
• nx run repo-tools:postinstall-script
• nx test scope-manager --coverage=false
• nx test typescript-eslint --coverage=false
• nx test parser --coverage=false
• nx test ast-spec --coverage=false
• nx run-many --target=build --parallel --exclude=website --exclude=website-eslint
• nx test eslint-plugin-internal --coverage=false
• nx test rule-schema-to-typescript-types --coverage=false
• nx run-many --target=lint --parallel --exclude eslint-plugin
• nx test typescript-estree
• nx test visitor-keys
• nx test utils
• nx test scope-manager
• nx test repo-tools
• nx test typescript-eslint
• nx test type-utils
• nx test parser
• nx test rule-schema-to-typescript-types
• nx test eslint-plugin-internal
• nx run integration-tests:test
• nx test ast-spec
• nx run-many --target=typecheck --parallel
• nx run repo-tools:generate-configs

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[abrahamguo]

@JoshuaKGoldberg should this be going into main or v8?
I wasn't sure since in #8211 @bradzacher mentioned this could be merged in ahead of v8.

[JoshuaKGoldberg]

LGTM, thanks for the port! 🙌

Just one suggestion on refactoring to a new file. If you don't like it I don't mind, and can merge as-is. Just let me know. 🙂

[JoshuaKGoldberg]

@JoshuaKGoldberg should this be going into main or v8? I wasn't sure since in #8211 @bradzacher mentioned this could be merged in ahead of v8.

👍 Let's do main, as you have it. I had that wonder too. 😄

[abrahamguo]

@JoshuaKGoldberg one curiosity question — how is this port of RuleTester unit-tested? I was surprised to not see a copy of all ESLint's unit tests against this class, and that I didn't need to add any new tests for the port of this feature.

[JoshuaKGoldberg]

D'oh! Sorry, brain fart this morning - there should be tests. See packages/rule-tester/tests/eslint-base/eslint-base.test.js.

[abrahamguo]

There are about 10-20 rules in eslint-plugin which have duplicate tests. Most of them seem to be merging multiple combinations of auto-generated tests together. I'm working on fixing them, but let me know if you have any thoughts on that.