463 lines
13 KiB
JavaScript
463 lines
13 KiB
JavaScript
/**
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* @fileoverview A rule to disallow the type conversions with shorter notations.
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* @author Toru Nagashima
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*/
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'use strict';
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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 INDEX_OF_PATTERN = /^(?:i|lastI)ndexOf$/u;
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const ALLOWABLE_OPERATORS = ['~', '!!', '+', '- -', '-', '*'];
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/**
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* Checks whether or not a node is a double logical negating.
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* @param {ASTNode} node An UnaryExpression node to check.
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* @returns {boolean} Whether or not the node is a double logical negating.
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*/
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function isDoubleLogicalNegating(node) {
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return (
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node.operator === '!' &&
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node.argument.type === 'UnaryExpression' &&
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node.argument.operator === '!'
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);
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}
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/**
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* Checks whether or not a node is a binary negating of `.indexOf()` method calling.
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* @param {ASTNode} node An UnaryExpression node to check.
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* @returns {boolean} Whether or not the node is a binary negating of `.indexOf()` method calling.
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*/
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function isBinaryNegatingOfIndexOf(node) {
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if (node.operator !== '~') {
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return false;
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}
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const callNode = astUtils.skipChainExpression(node.argument);
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return (
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callNode.type === 'CallExpression' &&
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astUtils.isSpecificMemberAccess(callNode.callee, null, INDEX_OF_PATTERN)
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);
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}
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/**
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* Checks whether or not a node is a multiplying by one.
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* @param {BinaryExpression} node A BinaryExpression node to check.
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* @returns {boolean} Whether or not the node is a multiplying by one.
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*/
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function isMultiplyByOne(node) {
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return (
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node.operator === '*' &&
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((node.left.type === 'Literal' && node.left.value === 1) ||
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(node.right.type === 'Literal' && node.right.value === 1))
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);
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}
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/**
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* Checks whether the given node logically represents multiplication by a fraction of `1`.
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* For example, `a * 1` in `a * 1 / b` is technically multiplication by `1`, but the
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* whole expression can be logically interpreted as `a * (1 / b)` rather than `(a * 1) / b`.
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* @param {BinaryExpression} node A BinaryExpression node to check.
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* @param {SourceCode} sourceCode The source code object.
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* @returns {boolean} Whether or not the node is a multiplying by a fraction of `1`.
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*/
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function isMultiplyByFractionOfOne(node, sourceCode) {
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return (
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node.type === 'BinaryExpression' &&
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node.operator === '*' &&
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node.right.type === 'Literal' &&
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node.right.value === 1 &&
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node.parent.type === 'BinaryExpression' &&
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node.parent.operator === '/' &&
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node.parent.left === node &&
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!astUtils.isParenthesised(sourceCode, node)
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);
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}
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/**
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* Checks whether the result of a node is numeric or not
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* @param {ASTNode} node The node to test
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* @returns {boolean} true if the node is a number literal or a `Number()`, `parseInt` or `parseFloat` call
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*/
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function isNumeric(node) {
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return (
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(node.type === 'Literal' && typeof node.value === 'number') ||
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(node.type === 'CallExpression' &&
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(node.callee.name === 'Number' ||
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node.callee.name === 'parseInt' ||
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node.callee.name === 'parseFloat'))
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);
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}
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/**
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* Returns the first non-numeric operand in a BinaryExpression. Designed to be
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* used from bottom to up since it walks up the BinaryExpression trees using
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* node.parent to find the result.
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* @param {BinaryExpression} node The BinaryExpression node to be walked up on
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* @returns {ASTNode|null} The first non-numeric item in the BinaryExpression tree or null
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*/
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function getNonNumericOperand(node) {
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const left = node.left,
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right = node.right;
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if (right.type !== 'BinaryExpression' && !isNumeric(right)) {
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return right;
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}
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if (left.type !== 'BinaryExpression' && !isNumeric(left)) {
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return left;
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}
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return null;
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}
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/**
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* Checks whether an expression evaluates to a string.
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* @param {ASTNode} node node that represents the expression to check.
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* @returns {boolean} Whether or not the expression evaluates to a string.
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*/
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function isStringType(node) {
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return (
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astUtils.isStringLiteral(node) ||
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(node.type === 'CallExpression' &&
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node.callee.type === 'Identifier' &&
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node.callee.name === 'String')
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);
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}
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/**
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* Checks whether a node is an empty string literal or not.
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* @param {ASTNode} node The node to check.
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* @returns {boolean} Whether or not the passed in node is an
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* empty string literal or not.
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*/
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function isEmptyString(node) {
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return (
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astUtils.isStringLiteral(node) &&
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(node.value === '' ||
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(node.type === 'TemplateLiteral' &&
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node.quasis.length === 1 &&
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node.quasis[0].value.cooked === ''))
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);
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}
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/**
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* Checks whether or not a node is a concatenating with an empty string.
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* @param {ASTNode} node A BinaryExpression node to check.
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* @returns {boolean} Whether or not the node is a concatenating with an empty string.
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*/
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function isConcatWithEmptyString(node) {
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return (
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node.operator === '+' &&
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((isEmptyString(node.left) && !isStringType(node.right)) ||
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(isEmptyString(node.right) && !isStringType(node.left)))
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);
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}
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/**
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* Checks whether or not a node is appended with an empty string.
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* @param {ASTNode} node An AssignmentExpression node to check.
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* @returns {boolean} Whether or not the node is appended with an empty string.
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*/
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function isAppendEmptyString(node) {
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return node.operator === '+=' && isEmptyString(node.right);
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}
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/**
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* Returns the operand that is not an empty string from a flagged BinaryExpression.
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* @param {ASTNode} node The flagged BinaryExpression node to check.
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* @returns {ASTNode} The operand that is not an empty string from a flagged BinaryExpression.
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*/
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function getNonEmptyOperand(node) {
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return isEmptyString(node.left) ? node.right : node.left;
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}
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//------------------------------------------------------------------------------
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// Rule Definition
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//------------------------------------------------------------------------------
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/** @type {import('../types').Rule.RuleModule} */
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module.exports = {
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meta: {
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hasSuggestions: true,
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type: 'suggestion',
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docs: {
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description: 'Disallow shorthand type conversions',
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recommended: false,
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frozen: true,
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url: 'https://eslint.org/docs/latest/rules/no-implicit-coercion',
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},
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fixable: 'code',
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schema: [
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{
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type: 'object',
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properties: {
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boolean: {
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type: 'boolean',
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},
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number: {
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type: 'boolean',
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},
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string: {
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type: 'boolean',
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},
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disallowTemplateShorthand: {
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type: 'boolean',
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},
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allow: {
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type: 'array',
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items: {
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enum: ALLOWABLE_OPERATORS,
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},
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uniqueItems: 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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defaultOptions: [
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{
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allow: [],
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boolean: true,
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disallowTemplateShorthand: false,
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number: true,
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string: true,
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},
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],
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messages: {
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implicitCoercion:
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'Unexpected implicit coercion encountered. Use `{{recommendation}}` instead.',
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useRecommendation: 'Use `{{recommendation}}` instead.',
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},
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},
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create(context) {
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const [options] = context.options;
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const sourceCode = context.sourceCode;
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/**
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* Reports an error and autofixes the node
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* @param {ASTNode} node An ast node to report the error on.
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* @param {string} recommendation The recommended code for the issue
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* @param {bool} shouldSuggest Whether this report should offer a suggestion
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* @param {bool} shouldFix Whether this report should fix the node
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* @returns {void}
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*/
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function report(node, recommendation, shouldSuggest, shouldFix) {
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/**
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* Fix function
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* @param {RuleFixer} fixer The fixer to fix.
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* @returns {Fix} The fix object.
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*/
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function fix(fixer) {
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const tokenBefore = sourceCode.getTokenBefore(node);
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if (
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tokenBefore?.range[1] === node.range[0] &&
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!astUtils.canTokensBeAdjacent(tokenBefore, recommendation)
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) {
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return fixer.replaceText(node, ` ${recommendation}`);
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}
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return fixer.replaceText(node, recommendation);
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}
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context.report({
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node,
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messageId: 'implicitCoercion',
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data: { recommendation },
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fix(fixer) {
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if (!shouldFix) {
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return null;
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}
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return fix(fixer);
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},
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suggest: [
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{
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messageId: 'useRecommendation',
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data: { recommendation },
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fix(fixer) {
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if (shouldFix || !shouldSuggest) {
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return null;
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}
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return fix(fixer);
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},
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},
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],
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});
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}
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return {
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UnaryExpression(node) {
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let operatorAllowed;
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// !!foo
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operatorAllowed = options.allow.includes('!!');
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if (
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!operatorAllowed &&
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options.boolean &&
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isDoubleLogicalNegating(node)
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) {
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const recommendation = `Boolean(${sourceCode.getText(node.argument.argument)})`;
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const variable = astUtils.getVariableByName(
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sourceCode.getScope(node),
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'Boolean'
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);
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const booleanExists = variable?.identifiers.length === 0;
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report(node, recommendation, true, booleanExists);
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}
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// ~foo.indexOf(bar)
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operatorAllowed = options.allow.includes('~');
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if (
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!operatorAllowed &&
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options.boolean &&
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isBinaryNegatingOfIndexOf(node)
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) {
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// `foo?.indexOf(bar) !== -1` will be true (== found) if the `foo` is nullish. So use `>= 0` in that case.
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const comparison =
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node.argument.type === 'ChainExpression' ? '>= 0' : '!== -1';
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const recommendation = `${sourceCode.getText(node.argument)} ${comparison}`;
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report(node, recommendation, false, false);
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}
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// +foo
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operatorAllowed = options.allow.includes('+');
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if (
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!operatorAllowed &&
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options.number &&
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node.operator === '+' &&
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!isNumeric(node.argument)
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) {
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const recommendation = `Number(${sourceCode.getText(node.argument)})`;
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report(node, recommendation, true, false);
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}
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// -(-foo)
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operatorAllowed = options.allow.includes('- -');
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if (
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!operatorAllowed &&
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options.number &&
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node.operator === '-' &&
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node.argument.type === 'UnaryExpression' &&
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node.argument.operator === '-' &&
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!isNumeric(node.argument.argument)
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) {
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const recommendation = `Number(${sourceCode.getText(node.argument.argument)})`;
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report(node, recommendation, true, false);
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}
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},
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// Use `:exit` to prevent double reporting
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'BinaryExpression:exit'(node) {
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let operatorAllowed;
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// 1 * foo
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operatorAllowed = options.allow.includes('*');
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const nonNumericOperand =
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!operatorAllowed &&
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options.number &&
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isMultiplyByOne(node) &&
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!isMultiplyByFractionOfOne(node, sourceCode) &&
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getNonNumericOperand(node);
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if (nonNumericOperand) {
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const recommendation = `Number(${sourceCode.getText(nonNumericOperand)})`;
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report(node, recommendation, true, false);
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}
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// foo - 0
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operatorAllowed = options.allow.includes('-');
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if (
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!operatorAllowed &&
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options.number &&
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node.operator === '-' &&
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node.right.type === 'Literal' &&
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node.right.value === 0 &&
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!isNumeric(node.left)
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) {
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const recommendation = `Number(${sourceCode.getText(node.left)})`;
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report(node, recommendation, true, false);
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}
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// "" + foo
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operatorAllowed = options.allow.includes('+');
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if (
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!operatorAllowed &&
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options.string &&
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isConcatWithEmptyString(node)
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) {
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const recommendation = `String(${sourceCode.getText(getNonEmptyOperand(node))})`;
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report(node, recommendation, true, false);
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}
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},
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AssignmentExpression(node) {
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// foo += ""
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const operatorAllowed = options.allow.includes('+');
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if (!operatorAllowed && options.string && isAppendEmptyString(node)) {
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const code = sourceCode.getText(getNonEmptyOperand(node));
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const recommendation = `${code} = String(${code})`;
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report(node, recommendation, true, false);
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}
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},
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TemplateLiteral(node) {
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if (!options.disallowTemplateShorthand) {
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return;
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}
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// tag`${foo}`
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if (node.parent.type === 'TaggedTemplateExpression') {
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return;
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}
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// `` or `${foo}${bar}`
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if (node.expressions.length !== 1) {
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return;
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}
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// `prefix${foo}`
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if (node.quasis[0].value.cooked !== '') {
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return;
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}
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// `${foo}postfix`
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if (node.quasis[1].value.cooked !== '') {
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return;
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}
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// if the expression is already a string, then this isn't a coercion
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if (isStringType(node.expressions[0])) {
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return;
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}
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const code = sourceCode.getText(node.expressions[0]);
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const recommendation = `String(${code})`;
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report(node, recommendation, true, false);
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},
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};
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},
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};
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