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							296 lines
						
					
					
						
							10 KiB
						
					
					
				/** | 
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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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 | 
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"use strict"; | 
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 | 
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const astUtils = require("./utils/ast-utils"); | 
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 | 
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//------------------------------------------------------------------------------ | 
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// Helpers | 
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//------------------------------------------------------------------------------ | 
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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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/** | 
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 * Parses and normalizes an option object. | 
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 * @param {Object} options An option object to parse. | 
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 * @returns {Object} The parsed and normalized option object. | 
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 */ | 
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function parseOptions(options) { | 
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    return { | 
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        boolean: "boolean" in options ? options.boolean : true, | 
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        number: "number" in options ? options.number : true, | 
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        string: "string" in options ? options.string : true, | 
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        allow: options.allow || [] | 
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    }; | 
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} | 
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 | 
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/** | 
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 * Checks whether or not a node is a double logical nigating. | 
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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 nigating. | 
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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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/** | 
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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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    return ( | 
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        node.operator === "~" && | 
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        node.argument.type === "CallExpression" && | 
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        node.argument.callee.type === "MemberExpression" && | 
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        node.argument.callee.property.type === "Identifier" && | 
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        INDEX_OF_PATTERN.test(node.argument.callee.property.name) | 
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    ); | 
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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 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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/** | 
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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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 | 
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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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 | 
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    if (right.type !== "BinaryExpression" && !isNumeric(right)) { | 
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        return right; | 
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    } | 
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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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 | 
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    return null; | 
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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 astUtils.isStringLiteral(node) && (node.value === "" || (node.type === "TemplateLiteral" && node.quasis.length === 1 && 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 node.operator === "+" && ( | 
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        (isEmptyString(node.left) && !astUtils.isStringLiteral(node.right)) || | 
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        (isEmptyString(node.right) && !astUtils.isStringLiteral(node.left)) | 
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    ); | 
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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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/** | 
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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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//------------------------------------------------------------------------------ | 
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// Rule Definition | 
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//------------------------------------------------------------------------------ | 
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 | 
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module.exports = { | 
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    meta: { | 
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        type: "suggestion", | 
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 | 
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        docs: { | 
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            description: "disallow shorthand type conversions", | 
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            category: "Best Practices", | 
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            recommended: false, | 
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            url: "https://eslint.org/docs/rules/no-implicit-coercion" | 
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        }, | 
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 | 
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        fixable: "code", | 
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 | 
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        schema: [{ | 
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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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                    default: true | 
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                }, | 
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                number: { | 
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                    type: "boolean", | 
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                    default: true | 
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                }, | 
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                string: { | 
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                    type: "boolean", | 
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                    default: true | 
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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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 | 
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    create(context) { | 
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        const options = parseOptions(context.options[0] || {}); | 
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        const sourceCode = context.getSourceCode(); | 
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 | 
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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} 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, shouldFix) { | 
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            context.report({ | 
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                node, | 
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                message: "use `{{recommendation}}` instead.", | 
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                data: { | 
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                    recommendation | 
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                }, | 
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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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 | 
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                    const tokenBefore = sourceCode.getTokenBefore(node); | 
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 | 
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                    if ( | 
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                        tokenBefore && | 
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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, ` ${recommendation}`); | 
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                    } | 
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                    return fixer.replaceText(node, recommendation); | 
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                } | 
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            }); | 
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        } | 
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 | 
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        return { | 
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            UnaryExpression(node) { | 
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                let operatorAllowed; | 
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 | 
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                // !!foo | 
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                operatorAllowed = options.allow.indexOf("!!") >= 0; | 
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                if (!operatorAllowed && options.boolean && isDoubleLogicalNegating(node)) { | 
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                    const recommendation = `Boolean(${sourceCode.getText(node.argument.argument)})`; | 
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 | 
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                    report(node, recommendation, true); | 
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                } | 
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 | 
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                // ~foo.indexOf(bar) | 
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                operatorAllowed = options.allow.indexOf("~") >= 0; | 
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                if (!operatorAllowed && options.boolean && isBinaryNegatingOfIndexOf(node)) { | 
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                    const recommendation = `${sourceCode.getText(node.argument)} !== -1`; | 
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 | 
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                    report(node, recommendation, false); | 
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                } | 
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 | 
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                // +foo | 
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                operatorAllowed = options.allow.indexOf("+") >= 0; | 
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                if (!operatorAllowed && options.number && node.operator === "+" && !isNumeric(node.argument)) { | 
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                    const recommendation = `Number(${sourceCode.getText(node.argument)})`; | 
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 | 
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                    report(node, recommendation, true); | 
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                } | 
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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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 | 
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                // 1 * foo | 
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                operatorAllowed = options.allow.indexOf("*") >= 0; | 
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                const nonNumericOperand = !operatorAllowed && options.number && isMultiplyByOne(node) && getNonNumericOperand(node); | 
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 | 
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                if (nonNumericOperand) { | 
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                    const recommendation = `Number(${sourceCode.getText(nonNumericOperand)})`; | 
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 | 
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                    report(node, recommendation, true); | 
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                } | 
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 | 
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                // "" + foo | 
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                operatorAllowed = options.allow.indexOf("+") >= 0; | 
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                if (!operatorAllowed && options.string && isConcatWithEmptyString(node)) { | 
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                    const recommendation = `String(${sourceCode.getText(getNonEmptyOperand(node))})`; | 
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 | 
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                    report(node, recommendation, true); | 
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                } | 
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            }, | 
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 | 
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            AssignmentExpression(node) { | 
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 | 
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                // foo += "" | 
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                const operatorAllowed = options.allow.indexOf("+") >= 0; | 
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 | 
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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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 | 
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                    report(node, recommendation, true); | 
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                } | 
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            } | 
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        }; | 
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    } | 
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};
 | 
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 |