fix: Correctly consume RuleTester statics

[bradzacher]

Prerequisites checklist

• I have read the contributing guidelines.

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

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

Tell us about your environment:

• ESLint Version: latest
• Node Version: 16
• npm Version: 8

What parser (default, @babel/eslint-parser, @typescript-eslint/parser, etc.) are you using? espree

Please show your full configuration:
N/A

What did you do? Please include the actual source code causing the issue.

const { RuleTester } = require("eslint")

class MyCustomRuleTesterSubclass extends RuleTester {}

const rule = (context) => ({});
const ruleTester = new MyCustomRuleTesterSubclass ();

MyCustomRuleTesterSubclass.it = (text, callback) => {
  console.log("MyCustomRuleTesterSubclass has been customized!")
}

ruleTester.run("repro", rule, {
  valid: ["var foo = 0;"],
  invalid: [],
});

runkit repl

What did you expect to happen?

This test should log out MyCustomRuleTesterSubclass has been customized!

What actually happened? Please include the actual, raw output from ESLint.

No console log.

If you instead set the it directly on RuleTester, it works.

This bug is caused because RuleTester directly references itself within its instance method instead of using this.constructor to reference the correct static context:

eslint/lib/rule-tester/rule-tester.js

Lines 980 to 1002 in 03ac8cf

	RuleTester.describe(ruleName, () => {
	RuleTester.describe("valid", () => {
	test.valid.forEach(valid => {
	RuleTester[valid.only ? "itOnly" : "it"](
	sanitize(typeof valid === "object" ? valid.name || valid.code : valid),
	() => {
	testValidTemplate(valid);
	}
	);
	});
	});
	RuleTester.describe("invalid", () => {
	test.invalid.forEach(invalid => {
	RuleTester[invalid.only ? "itOnly" : "it"](
	sanitize(invalid.name || invalid.code),
	() => {
	testInvalidTemplate(invalid);
	}
	);
	});
	});
	});

What changes did you make? (Give an overview)

• Convert RuleTester to use this.constructor instead of RuleTester to access static members.
• Add tests to prevent regressions

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

This was reported by a user of @typescript-eslint.
Fixes: typescript-eslint/typescript-eslint#4422

[linux-foundation-easycla]

The committers are authorized under a signed CLA.

• ✅ Brad Zacher (303806e)

[eslint-github-bot]

Hi @bradzacher!, thanks for the Pull Request

The first commit message isn't properly formatted. We ask that you update the message to match this format, as we use it to generate changelogs and automate releases.

• The length of the commit message must be less than or equal to 72

To Fix: You can fix this problem by running git commit --amend, editing your commit message, and then running git push -f to update this pull request.

Read more about contributing to ESLint here

[eslint-github-bot]

Hi @bradzacher!, thanks for the Pull Request

The first commit message isn't properly formatted. We ask that you update the message to match this format, as we use it to generate changelogs and automate releases.

• The length of the commit message must be less than or equal to 72

To Fix: You can fix this problem by running git commit --amend, editing your commit message, and then running git push -f to update this pull request.

Read more about contributing to ESLint here

[aladdin-add]

LGTM, thanks!

[nzakas]

LGTM. Thanks for fixing this.