@maniascript/mslint/dist/lib/rules/no-negated-condition.js

ManiaScript linter

import {} from '../linter/rule.js';
import { ConditionalStatement, UnaryExpression, BinaryExpression, UnaryOperator, BinaryOperator } from '@maniascript/parser';
export const noNegatedCondition = {
    meta: {
        id: 'no-negated-condition',
        description: 'Forbid negated conditions',
        recommended: true
    },
    create(context) {
        function hasOnlyElse(node) {
            return (node.branches.length === 2 &&
                node.branches[0].test !== undefined &&
                node.branches[1].test === undefined);
        }
        function isNegatedUnaryExpression(node) {
            return (node instanceof UnaryExpression &&
                node.operator === UnaryOperator['!']);
        }
        function isNegatedBinaryExpression(node) {
            return (node instanceof BinaryExpression &&
                node.operator === BinaryOperator['!=']);
        }
        function isNegatedIf(node) {
            const ifBranchTest = node.branches[0].test;
            return (ifBranchTest !== undefined && (isNegatedUnaryExpression(ifBranchTest) ||
                isNegatedBinaryExpression(ifBranchTest)));
        }
        return {
            'ConditionalStatement:enter': (node) => {
                if (node instanceof ConditionalStatement &&
                    hasOnlyElse(node) &&
                    isNegatedIf(node)) {
                    context.report(node.branches[0].test ?? node, 'Forbidden negated condition');
                }
            }
        };
    }
};