@maniascript/mslint/dist/lib/rules/no-dupe-else-if.js

ManiaScript linter

// Based on the no-dupe-else-if rule from eslint
// https://github.com/eslint/eslint/blob/main/lib/rules/no-dupe-else-if.js
import { sameTokens } from '../linter/ast-utils.js';
import { ConditionalStatement, LogicalExpression, LogicalOperator } from '@maniascript/parser';
function equal(a, b, tokens) {
    if (a.kind !== b.kind) {
        return false;
    }
    if (a instanceof LogicalExpression &&
        b instanceof LogicalExpression &&
        a.operator === b.operator) {
        return ((equal(a.left, b.left, tokens) && equal(a.right, b.right, tokens)) ||
            (equal(a.left, b.right, tokens) && equal(a.right, b.left, tokens)));
    }
    return sameTokens(a, b, tokens);
}
function isSubsetByComparator(comparator, arrayA, arrayB, tokens) {
    return arrayA.every(a => arrayB.some(b => comparator(a, b, tokens)));
}
const isSubset = isSubsetByComparator.bind(null, equal);
function splitByLogicalOperator(operator, node) {
    if (node instanceof LogicalExpression && node.operator === operator) {
        return [...splitByLogicalOperator(operator, node.left), ...splitByLogicalOperator(operator, node.right)];
    }
    return [node];
}
const splitByOr = splitByLogicalOperator.bind(null, LogicalOperator['||']);
const splitByAnd = splitByLogicalOperator.bind(null, LogicalOperator['&&']);
export const noDupeElseIf = {
    meta: {
        id: 'no-dupe-else-if',
        description: 'Forbid duplicate conditions in if-else-if chains',
        recommended: true
    },
    create(context) {
        return {
            'ConditionalStatement:exit': (node) => {
                if (node instanceof ConditionalStatement && node.branches.length > 1) {
                    const previousBranches = [];
                    for (const branch of node.branches) {
                        if (branch.test !== undefined) {
                            if (previousBranches.length > 0) {
                                const conditionsToCheck = (branch.test instanceof LogicalExpression &&
                                    branch.test.operator === LogicalOperator['&&'])
                                    ? [branch.test, ...splitByAnd(branch.test)]
                                    : [branch.test];
                                let listToCheck = conditionsToCheck.map(c => splitByOr(c).map(splitByAnd));
                                for (const previousBranch of previousBranches) {
                                    if (previousBranch.test !== undefined) {
                                        const currentOrOperands = splitByOr(previousBranch.test).map(splitByAnd);
                                        listToCheck = listToCheck.map(orOperands => orOperands.filter(orOperand => !currentOrOperands.some(currentOrOperand => isSubset(currentOrOperand, orOperand, context.tokens))));
                                        if (listToCheck.some(orOperands => orOperands.length === 0)) {
                                            context.report(branch.test, 'This branch will never be executed because its condition is already verified in a previous branch');
                                            break;
                                        }
                                    }
                                }
                            }
                            previousBranches.push(branch);
                        }
                    }
                }
            }
        };
    }
};