277 lines
9.3 KiB
JavaScript
277 lines
9.3 KiB
JavaScript
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/**
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* @fileoverview Rule to flag use of constructors without capital letters
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* @author Nicholas C. Zakas
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*/
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"use strict";
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//------------------------------------------------------------------------------
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// Requirements
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//------------------------------------------------------------------------------
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const astUtils = require("./utils/ast-utils");
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//------------------------------------------------------------------------------
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// Helpers
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//------------------------------------------------------------------------------
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const CAPS_ALLOWED = [
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"Array",
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"Boolean",
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"Date",
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"Error",
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"Function",
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"Number",
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"Object",
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"RegExp",
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"String",
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"Symbol",
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"BigInt"
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];
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/**
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* Ensure that if the key is provided, it must be an array.
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* @param {Object} obj Object to check with `key`.
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* @param {string} key Object key to check on `obj`.
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* @param {any} fallback If obj[key] is not present, this will be returned.
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* @throws {TypeError} If key is not an own array type property of `obj`.
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* @returns {string[]} Returns obj[key] if it's an Array, otherwise `fallback`
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*/
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function checkArray(obj, key, fallback) {
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/* c8 ignore start */
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if (Object.prototype.hasOwnProperty.call(obj, key) && !Array.isArray(obj[key])) {
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throw new TypeError(`${key}, if provided, must be an Array`);
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}/* c8 ignore stop */
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return obj[key] || fallback;
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}
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/**
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* A reducer function to invert an array to an Object mapping the string form of the key, to `true`.
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* @param {Object} map Accumulator object for the reduce.
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* @param {string} key Object key to set to `true`.
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* @returns {Object} Returns the updated Object for further reduction.
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*/
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function invert(map, key) {
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map[key] = true;
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return map;
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}
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/**
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* Creates an object with the cap is new exceptions as its keys and true as their values.
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* @param {Object} config Rule configuration
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* @returns {Object} Object with cap is new exceptions.
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*/
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function calculateCapIsNewExceptions(config) {
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let capIsNewExceptions = checkArray(config, "capIsNewExceptions", CAPS_ALLOWED);
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if (capIsNewExceptions !== CAPS_ALLOWED) {
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capIsNewExceptions = capIsNewExceptions.concat(CAPS_ALLOWED);
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}
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return capIsNewExceptions.reduce(invert, {});
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}
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//------------------------------------------------------------------------------
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// Rule Definition
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//------------------------------------------------------------------------------
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/** @type {import('../shared/types').Rule} */
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module.exports = {
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meta: {
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type: "suggestion",
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docs: {
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description: "Require constructor names to begin with a capital letter",
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recommended: false,
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url: "https://eslint.org/docs/latest/rules/new-cap"
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},
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schema: [
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{
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type: "object",
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properties: {
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newIsCap: {
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type: "boolean",
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default: true
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},
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capIsNew: {
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type: "boolean",
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default: true
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},
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newIsCapExceptions: {
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type: "array",
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items: {
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type: "string"
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}
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},
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newIsCapExceptionPattern: {
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type: "string"
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},
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capIsNewExceptions: {
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type: "array",
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items: {
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type: "string"
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}
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},
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capIsNewExceptionPattern: {
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type: "string"
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},
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properties: {
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type: "boolean",
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default: true
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}
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},
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additionalProperties: false
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}
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],
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messages: {
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upper: "A function with a name starting with an uppercase letter should only be used as a constructor.",
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lower: "A constructor name should not start with a lowercase letter."
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}
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},
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create(context) {
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const config = Object.assign({}, context.options[0]);
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config.newIsCap = config.newIsCap !== false;
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config.capIsNew = config.capIsNew !== false;
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const skipProperties = config.properties === false;
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const newIsCapExceptions = checkArray(config, "newIsCapExceptions", []).reduce(invert, {});
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const newIsCapExceptionPattern = config.newIsCapExceptionPattern ? new RegExp(config.newIsCapExceptionPattern, "u") : null;
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const capIsNewExceptions = calculateCapIsNewExceptions(config);
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const capIsNewExceptionPattern = config.capIsNewExceptionPattern ? new RegExp(config.capIsNewExceptionPattern, "u") : null;
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const listeners = {};
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const sourceCode = context.sourceCode;
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//--------------------------------------------------------------------------
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// Helpers
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//--------------------------------------------------------------------------
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/**
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* Get exact callee name from expression
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* @param {ASTNode} node CallExpression or NewExpression node
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* @returns {string} name
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*/
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function extractNameFromExpression(node) {
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return node.callee.type === "Identifier"
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? node.callee.name
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: astUtils.getStaticPropertyName(node.callee) || "";
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}
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/**
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* Returns the capitalization state of the string -
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* Whether the first character is uppercase, lowercase, or non-alphabetic
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* @param {string} str String
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* @returns {string} capitalization state: "non-alpha", "lower", or "upper"
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*/
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function getCap(str) {
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const firstChar = str.charAt(0);
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const firstCharLower = firstChar.toLowerCase();
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const firstCharUpper = firstChar.toUpperCase();
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if (firstCharLower === firstCharUpper) {
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// char has no uppercase variant, so it's non-alphabetic
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return "non-alpha";
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}
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if (firstChar === firstCharLower) {
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return "lower";
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}
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return "upper";
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}
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/**
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* Check if capitalization is allowed for a CallExpression
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* @param {Object} allowedMap Object mapping calleeName to a Boolean
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* @param {ASTNode} node CallExpression node
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* @param {string} calleeName Capitalized callee name from a CallExpression
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* @param {Object} pattern RegExp object from options pattern
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* @returns {boolean} Returns true if the callee may be capitalized
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*/
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function isCapAllowed(allowedMap, node, calleeName, pattern) {
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const sourceText = sourceCode.getText(node.callee);
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if (allowedMap[calleeName] || allowedMap[sourceText]) {
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return true;
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}
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if (pattern && pattern.test(sourceText)) {
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return true;
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}
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const callee = astUtils.skipChainExpression(node.callee);
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if (calleeName === "UTC" && callee.type === "MemberExpression") {
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// allow if callee is Date.UTC
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return callee.object.type === "Identifier" &&
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callee.object.name === "Date";
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}
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return skipProperties && callee.type === "MemberExpression";
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}
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/**
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* Reports the given messageId for the given node. The location will be the start of the property or the callee.
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* @param {ASTNode} node CallExpression or NewExpression node.
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* @param {string} messageId The messageId to report.
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* @returns {void}
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*/
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function report(node, messageId) {
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let callee = astUtils.skipChainExpression(node.callee);
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if (callee.type === "MemberExpression") {
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callee = callee.property;
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}
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context.report({ node, loc: callee.loc, messageId });
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}
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//--------------------------------------------------------------------------
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// Public
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//--------------------------------------------------------------------------
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if (config.newIsCap) {
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listeners.NewExpression = function(node) {
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const constructorName = extractNameFromExpression(node);
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if (constructorName) {
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const capitalization = getCap(constructorName);
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const isAllowed = capitalization !== "lower" || isCapAllowed(newIsCapExceptions, node, constructorName, newIsCapExceptionPattern);
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if (!isAllowed) {
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report(node, "lower");
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}
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}
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};
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}
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if (config.capIsNew) {
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listeners.CallExpression = function(node) {
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const calleeName = extractNameFromExpression(node);
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if (calleeName) {
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const capitalization = getCap(calleeName);
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const isAllowed = capitalization !== "upper" || isCapAllowed(capIsNewExceptions, node, calleeName, capIsNewExceptionPattern);
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if (!isAllowed) {
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report(node, "upper");
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}
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}
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};
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}
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return listeners;
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}
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};
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