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243 lines
9.3 KiB
243 lines
9.3 KiB
/**
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* @fileoverview Rule to flag statements that use magic numbers (adapted from https://github.com/danielstjules/buddy.js)
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* @author Vincent Lemeunier
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*/
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"use strict";
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const astUtils = require("./utils/ast-utils");
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// Maximum array length by the ECMAScript Specification.
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const MAX_ARRAY_LENGTH = 2 ** 32 - 1;
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//------------------------------------------------------------------------------
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// Rule Definition
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//------------------------------------------------------------------------------
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/**
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* Convert the value to bigint if it's a string. Otherwise return the value as-is.
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* @param {bigint|number|string} x The value to normalize.
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* @returns {bigint|number} The normalized value.
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*/
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function normalizeIgnoreValue(x) {
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if (typeof x === "string") {
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return BigInt(x.slice(0, -1));
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}
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return x;
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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: "Disallow magic numbers",
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recommended: false,
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url: "https://eslint.org/docs/latest/rules/no-magic-numbers"
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},
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schema: [{
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type: "object",
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properties: {
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detectObjects: {
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type: "boolean",
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default: false
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},
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enforceConst: {
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type: "boolean",
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default: false
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},
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ignore: {
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type: "array",
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items: {
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anyOf: [
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{ type: "number" },
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{ type: "string", pattern: "^[+-]?(?:0|[1-9][0-9]*)n$" }
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]
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},
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uniqueItems: true
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},
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ignoreArrayIndexes: {
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type: "boolean",
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default: false
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},
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ignoreDefaultValues: {
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type: "boolean",
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default: false
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},
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ignoreClassFieldInitialValues: {
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type: "boolean",
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default: false
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}
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},
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additionalProperties: false
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}],
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messages: {
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useConst: "Number constants declarations must use 'const'.",
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noMagic: "No magic number: {{raw}}."
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}
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},
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create(context) {
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const config = context.options[0] || {},
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detectObjects = !!config.detectObjects,
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enforceConst = !!config.enforceConst,
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ignore = new Set((config.ignore || []).map(normalizeIgnoreValue)),
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ignoreArrayIndexes = !!config.ignoreArrayIndexes,
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ignoreDefaultValues = !!config.ignoreDefaultValues,
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ignoreClassFieldInitialValues = !!config.ignoreClassFieldInitialValues;
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const okTypes = detectObjects ? [] : ["ObjectExpression", "Property", "AssignmentExpression"];
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/**
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* Returns whether the rule is configured to ignore the given value
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* @param {bigint|number} value The value to check
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* @returns {boolean} true if the value is ignored
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*/
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function isIgnoredValue(value) {
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return ignore.has(value);
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}
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/**
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* Returns whether the number is a default value assignment.
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* @param {ASTNode} fullNumberNode `Literal` or `UnaryExpression` full number node
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* @returns {boolean} true if the number is a default value
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*/
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function isDefaultValue(fullNumberNode) {
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const parent = fullNumberNode.parent;
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return parent.type === "AssignmentPattern" && parent.right === fullNumberNode;
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}
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/**
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* Returns whether the number is the initial value of a class field.
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* @param {ASTNode} fullNumberNode `Literal` or `UnaryExpression` full number node
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* @returns {boolean} true if the number is the initial value of a class field.
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*/
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function isClassFieldInitialValue(fullNumberNode) {
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const parent = fullNumberNode.parent;
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return parent.type === "PropertyDefinition" && parent.value === fullNumberNode;
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}
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/**
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* Returns whether the given node is used as a radix within parseInt() or Number.parseInt()
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* @param {ASTNode} fullNumberNode `Literal` or `UnaryExpression` full number node
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* @returns {boolean} true if the node is radix
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*/
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function isParseIntRadix(fullNumberNode) {
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const parent = fullNumberNode.parent;
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return parent.type === "CallExpression" && fullNumberNode === parent.arguments[1] &&
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(
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astUtils.isSpecificId(parent.callee, "parseInt") ||
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astUtils.isSpecificMemberAccess(parent.callee, "Number", "parseInt")
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);
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}
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/**
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* Returns whether the given node is a direct child of a JSX node.
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* In particular, it aims to detect numbers used as prop values in JSX tags.
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* Example: <input maxLength={10} />
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* @param {ASTNode} fullNumberNode `Literal` or `UnaryExpression` full number node
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* @returns {boolean} true if the node is a JSX number
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*/
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function isJSXNumber(fullNumberNode) {
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return fullNumberNode.parent.type.indexOf("JSX") === 0;
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}
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/**
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* Returns whether the given node is used as an array index.
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* Value must coerce to a valid array index name: "0", "1", "2" ... "4294967294".
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*
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* All other values, like "-1", "2.5", or "4294967295", are just "normal" object properties,
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* which can be created and accessed on an array in addition to the array index properties,
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* but they don't affect array's length and are not considered by methods such as .map(), .forEach() etc.
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*
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* The maximum array length by the specification is 2 ** 32 - 1 = 4294967295,
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* thus the maximum valid index is 2 ** 32 - 2 = 4294967294.
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*
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* All notations are allowed, as long as the value coerces to one of "0", "1", "2" ... "4294967294".
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*
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* Valid examples:
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* a[0], a[1], a[1.2e1], a[0xAB], a[0n], a[1n]
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* a[-0] (same as a[0] because -0 coerces to "0")
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* a[-0n] (-0n evaluates to 0n)
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*
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* Invalid examples:
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* a[-1], a[-0xAB], a[-1n], a[2.5], a[1.23e1], a[12e-1]
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* a[4294967295] (above the max index, it's an access to a regular property a["4294967295"])
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* a[999999999999999999999] (even if it wasn't above the max index, it would be a["1e+21"])
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* a[1e310] (same as a["Infinity"])
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* @param {ASTNode} fullNumberNode `Literal` or `UnaryExpression` full number node
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* @param {bigint|number} value Value expressed by the fullNumberNode
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* @returns {boolean} true if the node is a valid array index
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*/
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function isArrayIndex(fullNumberNode, value) {
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const parent = fullNumberNode.parent;
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return parent.type === "MemberExpression" && parent.property === fullNumberNode &&
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(Number.isInteger(value) || typeof value === "bigint") &&
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value >= 0 && value < MAX_ARRAY_LENGTH;
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}
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return {
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Literal(node) {
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if (!astUtils.isNumericLiteral(node)) {
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return;
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}
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let fullNumberNode;
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let value;
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let raw;
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// Treat unary minus as a part of the number
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if (node.parent.type === "UnaryExpression" && node.parent.operator === "-") {
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fullNumberNode = node.parent;
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value = -node.value;
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raw = `-${node.raw}`;
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} else {
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fullNumberNode = node;
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value = node.value;
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raw = node.raw;
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}
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const parent = fullNumberNode.parent;
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// Always allow radix arguments and JSX props
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if (
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isIgnoredValue(value) ||
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(ignoreDefaultValues && isDefaultValue(fullNumberNode)) ||
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(ignoreClassFieldInitialValues && isClassFieldInitialValue(fullNumberNode)) ||
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isParseIntRadix(fullNumberNode) ||
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isJSXNumber(fullNumberNode) ||
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(ignoreArrayIndexes && isArrayIndex(fullNumberNode, value))
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) {
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return;
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}
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if (parent.type === "VariableDeclarator") {
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if (enforceConst && parent.parent.kind !== "const") {
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context.report({
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node: fullNumberNode,
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messageId: "useConst"
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});
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}
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} else if (
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!okTypes.includes(parent.type) ||
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(parent.type === "AssignmentExpression" && parent.left.type === "Identifier")
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) {
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context.report({
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node: fullNumberNode,
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messageId: "noMagic",
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data: {
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raw
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}
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});
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}
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}
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};
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}
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};
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