feat: support TypeScript syntax in `default-param-last` by JoshuaKGoldberg · Pull Request #19431 · eslint/eslint

JoshuaKGoldberg · 2025-02-17T15:18:01Z

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What is the purpose of this pull request? (put an "X" next to an item)

[ ] Documentation update
[ ] Bug fix (template)
[ ] New rule (template)
[x] Changes an existing rule (template)
[ ] Add autofix to a rule
[ ] Add a CLI option
[ ] Add something to the core
[ ] Other, please explain:

What changes did you make? (Give an overview)

Starts on #19173.

Updates default-param-last to account for TypeScript syntax features as handled in the @typescript-eslint/default-param-last extension rule:

Class parameter properties
Type annotations

Includes tests equivalent to what the extension rule currently tests that's exclusive to TypeScript. They're in a separate ruleTesterTypeScript instance that uses @typescript-eslint/parser.

Also updates tools/check-rule-examples.js to allow TypeScript code block. Previously it only allowed JavaScript.

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

Should we also update documentation?

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nzakas

Thanks for getting this started. I left some points of clarification.

With regards to documentation, I think it would be good to add some code examples showing TypeScript.

I'm also wondering if maybe we should add something into meta indicating that this rule is TypeScript-aware?

Co-authored-by: Nicholas C. Zakas <nicholas@humanwhocodes.com>

pubmikeb · 2025-02-20T12:00:33Z

@JoshuaKGoldberg, I have a question: once this feature will be released, does it mean that ESLint could support the TypeScript linting out-of-box without any extra plugins or projects like typescript-eslint?

JoshuaKGoldberg · 2025-02-20T12:08:43Z

Depends what you mean by "TypeScript linting".

For syntax-only linting with just ESLint core rules, technically yes. See #19173 (comment) -> #19173 (comment) for a list of what will switch from needing a typescript-eslint extension rule to working out-of-the-box in ESLint core.

Typed linting, however, will not be supported in ESLint core. You'll still need typescript-eslint or an equivalent for that. See #19173 -> #19173 (comment).

ESLint core also presently doesn't have any plans that I know of to support TypeScript-specific rules that don't need typed linting. Example: @typescript-eslint/no-empty-object-type.

tl;dr: no, the strong recommendation from typescript-eslint going forward will still be to use typescript-eslint when linting TypeScript code.

nzakas · 2025-02-20T22:16:22Z

We discussed today and we're at least going to start with this:

meta.language = "javascript" - to indicate that this rule is meant for JavaScript or a derivative of it
meta.dialects = ["javascript", "typescript"] - to indicate that this rule is known to work with both plain JavaScript and TypeScript.

For now, I think this is enough and we don't need to get to deep into the difference between being syntax-aware and type-aware. We're not planning on displaying this info anywhere so in the short-term it will be mostly for our own edification but we are also looking at how we can use this info to, for example, automatically disable JavaScript-specific rules when linting JSON.

github-actions · 2025-03-07T22:31:16Z

Hi everyone, it looks like we lost track of this pull request. Please review and see what the next steps are. This pull request will auto-close in 7 days without an update.

Tanujkanti4441 · 2025-03-08T07:29:46Z

Not stale! waiting for a review.

nzakas · 2025-03-11T15:27:34Z

@JoshuaKGoldberg did you intended to include updates to check-rule-examples.js in this PR?

JoshuaKGoldberg · 2025-03-11T20:31:10Z

Ah, yes, and never mentioned this in the OP - editing it in now. Without the changes:

docs/src/rules/default-param-last.md
  56:4   error  Nonstandard language tag 'ts': use one of 'javascript', 'js' or 'jsx'
  59:20  error  Unexpected lint error found: Parsing error: Unexpected token :
  68:4   error  Nonstandard language tag 'ts': use one of 'javascript', 'js' or 'jsx'
  71:20  error  Unexpected lint error found: Parsing error: Unexpected token ?

nzakas

LGTM. Would like another review to double check the check-rule-examples changes.

Tanujkanti4441 · 2025-03-17T08:40:51Z

Sorry! closed it accidentally.

JoshuaKGoldberg · 2025-03-17T14:21:05Z

Coming over from https://github.com/eslint/eslint/pull/19431/files#r1991932318: this PR is accumulating more and more TypeScript support changes. Would it be preferable to split them out once everything is working into their own PR?

I see #19529 was also sent with some of the same changes.

nzakas · 2025-03-17T14:26:39Z

I think if we hide "Open in Playground" for now, that's enough to merge this. The playground changes may take a bit to get working and we can always iterate on the error location in a separate PR.

mdjermanovic · 2025-03-17T15:14:18Z

I think if we hide "Open in Playground" for now, that's enough to merge this. The playground changes may take a bit to get working and we can always iterate on the error location in a separate PR.

Agreed.

mdjermanovic

LGTM, thanks!

This PR contains the following updates: | Package | Type | Update | Change | |---|---|---|---| | [@eslint/js](https://eslint.org) ([source](https://github.com/eslint/eslint/tree/HEAD/packages/js)) | devDependencies | minor | [`9.22.0` -> `9.23.0`](https://renovatebot.com/diffs/npm/@eslint%2fjs/9.22.0/9.23.0) | | [eslint](https://eslint.org) ([source](https://github.com/eslint/eslint)) | devDependencies | minor | [`9.22.0` -> `9.23.0`](https://renovatebot.com/diffs/npm/eslint/9.22.0/9.23.0) | --- ### Release Notes <details> <summary>eslint/eslint (@eslint/js)</summary> ### [`v9.23.0`](https://github.com/eslint/eslint/releases/tag/v9.23.0) [Compare Source](eslint/eslint@v9.22.0...v9.23.0) ##### Features - [`557a0d2`](eslint/eslint@557a0d2) feat: support TypeScript syntax in no-useless-constructor ([#19535](eslint/eslint#19535)) (Josh Goldberg ✨) - [`8320241`](eslint/eslint@8320241) feat: support TypeScript syntax in `default-param-last` ([#19431](eslint/eslint#19431)) (Josh Goldberg ✨) - [`833c4a3`](eslint/eslint@833c4a3) feat: defineConfig() supports "flat/" config prefix ([#19533](eslint/eslint#19533)) (Nicholas C. Zakas) - [`4a0df16`](eslint/eslint@4a0df16) feat: circular autofix/conflicting rules detection ([#19514](eslint/eslint#19514)) (Milos Djermanovic) - [`be56a68`](eslint/eslint@be56a68) feat: support TypeScript syntax in `class-methods-use-this` ([#19498](eslint/eslint#19498)) (Josh Goldberg ✨) ##### Bug Fixes - [`0e20aa7`](eslint/eslint@0e20aa7) fix: move deprecated `RuleContext` methods to subtype ([#19531](eslint/eslint#19531)) (Francesco Trotta) - [`cc3bd00`](eslint/eslint@cc3bd00) fix: reporting variable used in catch block in `no-useless-assignment` ([#19423](eslint/eslint#19423)) (Tanuj Kanti) - [`d46ff83`](eslint/eslint@d46ff83) fix: `no-dupe-keys` false positive with proto setter ([#19508](eslint/eslint#19508)) (Milos Djermanovic) - [`e732773`](eslint/eslint@e732773) fix: navigation of search results on pressing Enter ([#19502](eslint/eslint#19502)) (Tanuj Kanti) - [`f4e9c5f`](eslint/eslint@f4e9c5f...

feat: support TypeScript syntax in default-param-last

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JoshuaKGoldberg requested a review from a team as a code owner February 17, 2025 15:18

eslint-github-bot Bot added the feature This change adds a new feature to ESLint label Feb 17, 2025

github-actions Bot added the rule Relates to ESLint's core rules label Feb 17, 2025

JoshuaKGoldberg mentioned this pull request Feb 17, 2025

Change Request: Make rules TypeScript syntax-aware #19173

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nzakas requested changes Feb 17, 2025

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Comment thread lib/rules/default-param-last.js Outdated

Comment thread lib/rules/default-param-last.js Outdated

Comment thread lib/rules/default-param-last.js Outdated

Comment thread lib/rules/default-param-last.js Outdated

Comment thread lib/rules/default-param-last.js Outdated

JoshuaKGoldberg and others added 2 commits February 17, 2025 14:44

Apply suggestions from code review

ba34e02

Co-authored-by: Nicholas C. Zakas <nicholas@humanwhocodes.com>

Simplify naming and runtime logic

0067ce1

JoshuaKGoldberg requested a review from nzakas February 17, 2025 20:06

JoshuaKGoldberg commented Feb 19, 2025

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Comment thread lib/rules/default-param-last.js

JoshuaKGoldberg added 3 commits February 19, 2025 07:35

Added ```ts support to rule docs examples

b74684e

nit: parser name

e50d4f9

meta.docs.typescript: 'syntax'

04188ea

JoshuaKGoldberg commented Feb 19, 2025

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Comment thread lib/rules/default-param-last.js Outdated

fix: example tooling tests

de59b04

Add: meta.dialects, language

b7b964a

JoshuaKGoldberg commented Feb 24, 2025

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Comment thread lib/rules/default-param-last.js

github-actions Bot added the Stale label Mar 7, 2025

Tanujkanti4441 removed the Stale label Mar 8, 2025

Remove the typescript: syntax

930e45a

JoshuaKGoldberg mentioned this pull request Mar 10, 2025

feat: support TypeScript syntax in class-methods-use-this #19498

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nzakas previously approved these changes Mar 12, 2025

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nzakas moved this from Implementing to Second Review Needed in Triage Mar 12, 2025

mdjermanovic reviewed Mar 12, 2025

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Comment thread docs/src/rules/default-param-last.md

Tanujkanti4441 closed this Mar 17, 2025

github-project-automation Bot moved this from Second Review Needed to Complete in Triage Mar 17, 2025

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github-project-automation Bot moved this from Complete to Evaluating in Triage Mar 17, 2025

JoshuaKGoldberg mentioned this pull request Mar 17, 2025

Suggestion: Support TypeScript syntax in playground eslint/eslint.org#709

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Don't render playground links for ts code blocks

edecb67

JoshuaKGoldberg dismissed nzakas’s stale review via edecb67 March 17, 2025 14:19

nzakas mentioned this pull request Mar 17, 2025

docs: support TypeScript language tags in rule documentation #19529

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JoshuaKGoldberg moved this from Evaluating to Implementing in Triage Mar 17, 2025

JoshuaKGoldberg moved this from Implementing to Evaluating in Triage Mar 17, 2025

Tanujkanti4441 added the accepted There is consensus among the team that this change meets the criteria for inclusion label Mar 18, 2025

Tanujkanti4441 moved this from Evaluating to Implementing in Triage Mar 18, 2025

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mdjermanovic merged commit 8320241 into eslint:main Mar 18, 2025
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github-project-automation Bot moved this from Implementing to Complete in Triage Mar 18, 2025

JoshuaKGoldberg deleted the default-param-last-typescript-syntax branch March 18, 2025 22:44

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