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Rosanny Sihombing authoredThis reverts merge request !169
5b5df7d0
/** * @fileoverview Rule to disallow duplicate conditions in if-else-if chains * @author Milos Djermanovic */"use strict";//------------------------------------------------------------------------------// Requirements//------------------------------------------------------------------------------const astUtils = require("./utils/ast-utils");//------------------------------------------------------------------------------// Helpers//------------------------------------------------------------------------------/** * Determines whether the first given array is a subset of the second given array. * @param {Function} comparator A function to compare two elements, should return `true` if they are equal. * @param {Array} arrA The array to compare from. * @param {Array} arrB The array to compare against. * @returns {boolean} `true` if the array `arrA` is a subset of the array `arrB`. */function isSubsetByComparator(comparator, arrA, arrB) { return arrA.every(a => arrB.some(b => comparator(a, b)));}/** * Splits the given node by the given logical operator. * @param {string} operator Logical operator `||` or `&&`. * @param {ASTNode} node The node to split. * @returns {ASTNode[]} Array of conditions that makes the node when joined by the operator. */function splitByLogicalOperator(operator, node) { if (node.type === "LogicalExpression" && node.operator === operator) { return [...splitByLogicalOperator(operator, node.left), ...splitByLogicalOperator(operator, node.right)]; } return [node];}const splitByOr = splitByLogicalOperator.bind(null, "||");const splitByAnd = splitByLogicalOperator.bind(null, "&&");//------------------------------------------------------------------------------// Rule Definition//------------------------------------------------------------------------------module.exports = { meta: { type: "problem", docs: { description: "disallow duplicate conditions in if-else-if chains", category: "Possible Errors", recommended: true, url: "https://eslint.org/docs/rules/no-dupe-else-if" }, schema: [], messages: { unexpected: "This branch can never execute. Its condition is a duplicate or covered by previous conditions in the if-else-if chain." } }, create(context) { const sourceCode = context.getSourceCode(); /**
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* Determines whether the two given nodes are considered to be equal. In particular, given that the nodes
* represent expressions in a boolean context, `||` and `&&` can be considered as commutative operators.
* @param {ASTNode} a First node.
* @param {ASTNode} b Second node.
* @returns {boolean} `true` if the nodes are considered to be equal.
*/
function equal(a, b) {
if (a.type !== b.type) {
return false;
}
if (
a.type === "LogicalExpression" &&
(a.operator === "||" || a.operator === "&&") &&
a.operator === b.operator
) {
return equal(a.left, b.left) && equal(a.right, b.right) ||
equal(a.left, b.right) && equal(a.right, b.left);
}
return astUtils.equalTokens(a, b, sourceCode);
}
const isSubset = isSubsetByComparator.bind(null, equal);
return {
IfStatement(node) {
const test = node.test,
conditionsToCheck = test.type === "LogicalExpression" && test.operator === "&&"
? [test, ...splitByAnd(test)]
: [test];
let current = node,
listToCheck = conditionsToCheck.map(c => splitByOr(c).map(splitByAnd));
while (current.parent && current.parent.type === "IfStatement" && current.parent.alternate === current) {
current = current.parent;
const currentOrOperands = splitByOr(current.test).map(splitByAnd);
listToCheck = listToCheck.map(orOperands => orOperands.filter(
orOperand => !currentOrOperands.some(currentOrOperand => isSubset(currentOrOperand, orOperand))
));
if (listToCheck.some(orOperands => orOperands.length === 0)) {
context.report({ node: test, messageId: "unexpected" });
break;
}
}
}
};
}
};