sindresorhus/eslint-plugin-unicorn

Rule proposal: `prefer-private-class-fields`

Closed

#979 opened on Jan 1, 2021

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help wantednew rule

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Description

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes/Private_class_fields

Prefer private fields over the convention of underscore prefixed names.

This feature requires Node.js 12, so we cannot add it to the recommended preset until April 2021 (date of Node.js 10 obsoletion).

Does ESLint support this feature yet?

Fail

class Foo {
	static _PRIVATE_STATIC_FIELD

	_privateField

	_privateMethod() {
		return 'hello world'
	}
}

Pass

class Foo {
	static #PRIVATE_STATIC_FIELD

	#privateField

	#privateMethod() {
		return 'hello world'
	}
}

Contributor guide

Research direction
Review existing rules in the 'rules/' directory of eslint plugin unicorn for structure and ESLint API usage. The rule should detect class fields prefixed with underscore and suggest replacing with '#' private fields. Ensure compatibility with Node.js >=12 by checking AST node types. Reference the provided MDN documentation and ESLint guide on custom rules.
Tech stack
javascript
Domain
tooling
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
ESLint custom rule developmentJavaScript private class fields
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
55