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Diffstat (limited to 'tools/node_modules/eslint/lib/rules/no-dupe-else-if.js')
-rw-r--r-- | tools/node_modules/eslint/lib/rules/no-dupe-else-if.js | 122 |
1 files changed, 122 insertions, 0 deletions
diff --git a/tools/node_modules/eslint/lib/rules/no-dupe-else-if.js b/tools/node_modules/eslint/lib/rules/no-dupe-else-if.js new file mode 100644 index 0000000000..a165e16607 --- /dev/null +++ b/tools/node_modules/eslint/lib/rules/no-dupe-else-if.js @@ -0,0 +1,122 @@ +/** + * @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: false, + 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(); + + /** + * 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; + } + } + } + }; + } +}; |