/** * @fileoverview Prevent usage of Array index in keys * @author Joe Lencioni */ 'use strict'; const has = require('object.hasown/polyfill')(); const astUtil = require('../util/ast'); const docsUrl = require('../util/docsUrl'); const pragma = require('../util/pragma'); const report = require('../util/report'); const variableUtil = require('../util/variable'); // ------------------------------------------------------------------------------ // Rule Definition // ------------------------------------------------------------------------------ function isCreateCloneElement(node, context) { if (!node) { return false; } if (node.type === 'MemberExpression' || node.type === 'OptionalMemberExpression') { return node.object && node.object.name === pragma.getFromContext(context) && ['createElement', 'cloneElement'].indexOf(node.property.name) !== -1; } if (node.type === 'Identifier') { const variable = variableUtil.findVariableByName(context, node, node.name); if (variable && variable.type === 'ImportSpecifier') { return variable.parent.source.value === 'react'; } } return false; } const messages = { noArrayIndex: 'Do not use Array index in keys', }; /** @type {import('eslint').Rule.RuleModule} */ module.exports = { meta: { docs: { description: 'Disallow usage of Array index in keys', category: 'Best Practices', recommended: false, url: docsUrl('no-array-index-key'), }, messages, schema: [], }, create(context) { // -------------------------------------------------------------------------- // Public // -------------------------------------------------------------------------- const indexParamNames = []; const iteratorFunctionsToIndexParamPosition = { every: 1, filter: 1, find: 1, findIndex: 1, flatMap: 1, forEach: 1, map: 1, reduce: 2, reduceRight: 2, some: 1, }; function isArrayIndex(node) { return node.type === 'Identifier' && indexParamNames.indexOf(node.name) !== -1; } function isUsingReactChildren(node) { const callee = node.callee; if ( !callee || !callee.property || !callee.object ) { return null; } const isReactChildMethod = ['map', 'forEach'].indexOf(callee.property.name) > -1; if (!isReactChildMethod) { return null; } const obj = callee.object; if (obj && obj.name === 'Children') { return true; } if (obj && obj.object && obj.object.name === pragma.getFromContext(context)) { return true; } return false; } function getMapIndexParamName(node) { const callee = node.callee; if (callee.type !== 'MemberExpression' && callee.type !== 'OptionalMemberExpression') { return null; } if (callee.property.type !== 'Identifier') { return null; } if (!has(iteratorFunctionsToIndexParamPosition, callee.property.name)) { return null; } const callbackArg = isUsingReactChildren(node) ? node.arguments[1] : node.arguments[0]; if (!callbackArg) { return null; } if (!astUtil.isFunctionLikeExpression(callbackArg)) { return null; } const params = callbackArg.params; const indexParamPosition = iteratorFunctionsToIndexParamPosition[callee.property.name]; if (params.length < indexParamPosition + 1) { return null; } return params[indexParamPosition].name; } function getIdentifiersFromBinaryExpression(side) { if (side.type === 'Identifier') { return side; } if (side.type === 'BinaryExpression') { // recurse const left = getIdentifiersFromBinaryExpression(side.left); const right = getIdentifiersFromBinaryExpression(side.right); return [].concat(left, right).filter(Boolean); } return null; } function checkPropValue(node) { if (isArrayIndex(node)) { // key={bar} report(context, messages.noArrayIndex, 'noArrayIndex', { node, }); return; } if (node.type === 'TemplateLiteral') { // key={`foo-${bar}`} node.expressions.filter(isArrayIndex).forEach(() => { report(context, messages.noArrayIndex, 'noArrayIndex', { node, }); }); return; } if (node.type === 'BinaryExpression') { // key={'foo' + bar} const identifiers = getIdentifiersFromBinaryExpression(node); identifiers.filter(isArrayIndex).forEach(() => { report(context, messages.noArrayIndex, 'noArrayIndex', { node, }); }); return; } if (node.type === 'CallExpression' && node.callee && node.callee.type === 'MemberExpression' && node.callee.object && isArrayIndex(node.callee.object) && node.callee.property && node.callee.property.type === 'Identifier' && node.callee.property.name === 'toString' ) { // key={bar.toString()} report(context, messages.noArrayIndex, 'noArrayIndex', { node, }); return; } if (node.type === 'CallExpression' && node.callee && node.callee.type === 'Identifier' && node.callee.name === 'String' && Array.isArray(node.arguments) && node.arguments.length > 0 && isArrayIndex(node.arguments[0]) ) { // key={String(bar)} report(context, messages.noArrayIndex, 'noArrayIndex', { node: node.arguments[0], }); } } function popIndex(node) { const mapIndexParamName = getMapIndexParamName(node); if (!mapIndexParamName) { return; } indexParamNames.pop(); } return { 'CallExpression, OptionalCallExpression'(node) { if (isCreateCloneElement(node.callee, context) && node.arguments.length > 1) { // React.createElement if (!indexParamNames.length) { return; } const props = node.arguments[1]; if (props.type !== 'ObjectExpression') { return; } props.properties.forEach((prop) => { if (!prop.key || prop.key.name !== 'key') { // { ...foo } // { foo: bar } return; } checkPropValue(prop.value); }); return; } const mapIndexParamName = getMapIndexParamName(node); if (!mapIndexParamName) { return; } indexParamNames.push(mapIndexParamName); }, JSXAttribute(node) { if (node.name.name !== 'key') { // foo={bar} return; } if (!indexParamNames.length) { // Not inside a call expression that we think has an index param. return; } const value = node.value; if (!value || value.type !== 'JSXExpressionContainer') { // key='foo' or just simply 'key' return; } checkPropValue(value.expression); }, 'CallExpression:exit': popIndex, 'OptionalCallExpression:exit': popIndex, }; }, };