eslint-plugin-unicorn/rules/no-useless-fallback-in-spread.js

More than 300 powerful ESLint rules

import {
	isParenthesized,
	getParenthesizedRange,
} from './utils/index.js';
import {removeParentheses} from './fix/index.js';
import {isEmptyObjectExpression} from './ast/index.js';

const MESSAGE_ID = 'no-useless-fallback-in-spread';
const messages = {
	[MESSAGE_ID]: 'The empty object is useless.',
};

/** @param {import('eslint').Rule.RuleContext} context */
const create = context => {
	// `{...(foo || {})}`, `{...(foo ?? {})}`
	context.on('ObjectExpression', node => {
		if (!(
			isEmptyObjectExpression(node)
			&& node.parent.type === 'LogicalExpression'
			&& node.parent.right === node
			&& (node.parent.operator === '||' || node.parent.operator === '??')
			&& node.parent.parent.type === 'SpreadElement'
			&& node.parent.parent.argument === node.parent
			&& node.parent.parent.parent.type === 'ObjectExpression'
			&& node.parent.parent.parent.properties.includes(node.parent.parent)
		)) {
			return;
		}

		return {
			node,
			messageId: MESSAGE_ID,
			/** @param {import('eslint').Rule.RuleFixer} fixer */
			* fix(fixer, {abort}) {
				const {sourceCode} = context;
				const logicalExpression = node.parent;

				// Don't drop comments around `||`/`??` or the empty object.
				if (sourceCode.getCommentsInside(logicalExpression).length > 0) {
					return abort();
				}

				const {left} = logicalExpression;
				const isLeftObjectParenthesized = isParenthesized(left, context);
				const [, start] = isLeftObjectParenthesized
					? getParenthesizedRange(left, context)
					: sourceCode.getRange(left);
				const [, end] = sourceCode.getRange(logicalExpression);

				yield fixer.removeRange([start, end]);

				if (
					isLeftObjectParenthesized
					|| left.type !== 'SequenceExpression'
				) {
					yield removeParentheses(logicalExpression, fixer, context);
				}
			},
		};
	});
};

/** @type {import('eslint').Rule.RuleModule} */
const config = {
	create,
	meta: {
		type: 'suggestion',
		docs: {
			description: 'Disallow useless fallback when spreading in object literals.',
			recommended: 'unopinionated',
		},
		fixable: 'code',
		messages,
		languages: [
			'js/js',
		],
	},
};

export default config;