eslint-plugin-unicorn/rules/prefer-type-error.js

More than 100 powerful ESLint rules

import {isNewExpression} from './ast/index.js';

const MESSAGE_ID = 'prefer-type-error';
const messages = {
	[MESSAGE_ID]: '`new Error()` is too unspecific for a type check. Use `new TypeError()` instead.',
};

const typeCheckIdentifiers = new Set([
	'isArguments',
	'isArray',
	'isArrayBuffer',
	'isArrayLike',
	'isArrayLikeObject',
	'isBigInt',
	'isBoolean',
	'isBuffer',
	'isDate',
	'isElement',
	'isError',
	'isFinite',
	'isFunction',
	'isInteger',
	'isLength',
	'isMap',
	'isNaN',
	'isNative',
	'isNil',
	'isNull',
	'isNumber',
	'isObject',
	'isObjectLike',
	'isPlainObject',
	'isPrototypeOf',
	'isRegExp',
	'isSafeInteger',
	'isSet',
	'isString',
	'isSymbol',
	'isTypedArray',
	'isUndefined',
	'isView',
	'isWeakMap',
	'isWeakSet',
	'isWindow',
	'isXMLDoc',
]);

const typeCheckGlobalIdentifiers = new Set([
	'isNaN',
	'isFinite',
]);

const isTypecheckingIdentifier = (node, callExpression, isMemberExpression) =>
	callExpression !== undefined
	&& callExpression.arguments.length > 0
	&& node.type === 'Identifier'
	&& (
		(isMemberExpression === true && typeCheckIdentifiers.has(node.name))
		|| (isMemberExpression === false && typeCheckGlobalIdentifiers.has(node.name))
	);

const isLone = node => node.parent && node.parent.body && node.parent.body.length === 1;

const isTypecheckingMemberExpression = (node, callExpression) => {
	if (isTypecheckingIdentifier(node.property, callExpression, true)) {
		return true;
	}

	if (node.object.type === 'MemberExpression') {
		return isTypecheckingMemberExpression(node.object, callExpression);
	}

	return false;
};

const isTypecheckingExpression = (node, callExpression) => {
	switch (node.type) {
		case 'Identifier': {
			return isTypecheckingIdentifier(node, callExpression, false);
		}

		case 'MemberExpression': {
			return isTypecheckingMemberExpression(node, callExpression);
		}

		case 'CallExpression': {
			return isTypecheckingExpression(node.callee, node);
		}

		case 'UnaryExpression': {
			return (
				node.operator === 'typeof'
				|| (node.operator === '!' && isTypecheckingExpression(node.argument))
			);
		}

		case 'BinaryExpression': {
			return (
				node.operator === 'instanceof'
				|| isTypecheckingExpression(node.left, callExpression)
				|| isTypecheckingExpression(node.right, callExpression)
			);
		}

		case 'LogicalExpression': {
			return (
				isTypecheckingExpression(node.left, callExpression)
				&& isTypecheckingExpression(node.right, callExpression)
			);
		}

		default: {
			return false;
		}
	}
};

const isTypechecking = node => node.type === 'IfStatement' && isTypecheckingExpression(node.test);

/** @param {import('eslint').Rule.RuleContext} context */
const create = () => ({
	ThrowStatement(node) {
		if (
			isNewExpression(node.argument, {name: 'Error'})
			&& isLone(node)
			&& node.parent.parent
			&& isTypechecking(node.parent.parent)
		) {
			const errorConstructor = node.argument.callee;
			return {
				node: errorConstructor,
				messageId: MESSAGE_ID,
				fix: fixer => fixer.insertTextBefore(errorConstructor, 'Type'),
			};
		}
	},
});

/** @type {import('eslint').Rule.RuleModule} */
const config = {
	create,
	meta: {
		type: 'suggestion',
		docs: {
			description: 'Enforce throwing `TypeError` in type checking conditions.',
			recommended: true,
		},
		fixable: 'code',
		messages,
	},
};

export default config;