eslint-plugin-unicorn/rules/prefer-optional-catch-binding.js

More than 100 powerful ESLint rules

import {isOpeningParenToken, isClosingParenToken} from '@eslint-community/eslint-utils';
import assertToken from './utils/assert-token.js';

const MESSAGE_ID_WITH_NAME = 'with-name';
const MESSAGE_ID_WITHOUT_NAME = 'without-name';
const messages = {
	[MESSAGE_ID_WITH_NAME]: 'Remove unused catch binding `{{name}}`.',
	[MESSAGE_ID_WITHOUT_NAME]: 'Remove unused catch binding.',
};

/** @param {import('eslint').Rule.RuleContext} context */
const create = context => ({
	CatchClause(catchClause) {
		const node = catchClause.param;
		if (!node) {
			return;
		}

		const {sourceCode} = context;
		const variables = sourceCode.getDeclaredVariables(node.parent);

		if (variables.some(variable => variable.references.length > 0)) {
			return;
		}

		const {type, name, parent} = node;

		return {
			node,
			messageId: type === 'Identifier' ? MESSAGE_ID_WITH_NAME : MESSAGE_ID_WITHOUT_NAME,
			data: {name},
			* fix(fixer) {
				const tokenBefore = sourceCode.getTokenBefore(node);
				assertToken(tokenBefore, {
					test: isOpeningParenToken,
					expected: '(',
					ruleId: 'prefer-optional-catch-binding',
				});

				const tokenAfter = sourceCode.getTokenAfter(node);
				assertToken(tokenAfter, {
					test: isClosingParenToken,
					expected: ')',
					ruleId: 'prefer-optional-catch-binding',
				});

				yield fixer.remove(tokenBefore);
				yield fixer.remove(node);
				yield fixer.remove(tokenAfter);

				const [, endOfClosingParenthesis] = sourceCode.getRange(tokenAfter);
				const [startOfCatchClauseBody] = sourceCode.getRange(parent.body);
				const text = sourceCode.text.slice(endOfClosingParenthesis, startOfCatchClauseBody);
				const leadingSpacesLength = text.length - text.trimStart().length;
				if (leadingSpacesLength !== 0) {
					yield fixer.removeRange([endOfClosingParenthesis, endOfClosingParenthesis + leadingSpacesLength]);
				}
			},
		};
	},
});

/** @type {import('eslint').Rule.RuleModule} */
const config = {
	create,
	meta: {
		type: 'suggestion',
		docs: {
			description: 'Prefer omitting the `catch` binding parameter.',
			recommended: true,
		},
		fixable: 'code',
		messages,
	},
};

export default config;