298 lines
11 KiB
JavaScript
298 lines
11 KiB
JavaScript
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/**
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* @fileoverview Prefer destructuring from arrays and objects
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* @author Alex LaFroscia
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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 PRECEDENCE_OF_ASSIGNMENT_EXPR = astUtils.getPrecedence({ type: "AssignmentExpression" });
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//------------------------------------------------------------------------------
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// Rule Definition
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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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docs: {
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description: "require destructuring from arrays and/or objects",
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category: "ECMAScript 6",
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recommended: false,
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url: "https://eslint.org/docs/rules/prefer-destructuring"
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},
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fixable: "code",
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schema: [
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{
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/*
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* old support {array: Boolean, object: Boolean}
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* new support {VariableDeclarator: {}, AssignmentExpression: {}}
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*/
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oneOf: [
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{
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type: "object",
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properties: {
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VariableDeclarator: {
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type: "object",
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properties: {
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array: {
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type: "boolean"
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},
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object: {
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type: "boolean"
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}
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},
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additionalProperties: false
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},
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AssignmentExpression: {
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type: "object",
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properties: {
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array: {
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type: "boolean"
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},
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object: {
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type: "boolean"
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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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additionalProperties: false
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},
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{
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type: "object",
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properties: {
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array: {
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type: "boolean"
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},
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object: {
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type: "boolean"
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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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{
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type: "object",
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properties: {
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enforceForRenamedProperties: {
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type: "boolean"
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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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preferDestructuring: "Use {{type}} destructuring."
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}
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},
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create(context) {
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const enabledTypes = context.options[0];
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const enforceForRenamedProperties = context.options[1] && context.options[1].enforceForRenamedProperties;
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let normalizedOptions = {
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VariableDeclarator: { array: true, object: true },
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AssignmentExpression: { array: true, object: true }
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};
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if (enabledTypes) {
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normalizedOptions = typeof enabledTypes.array !== "undefined" || typeof enabledTypes.object !== "undefined"
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? { VariableDeclarator: enabledTypes, AssignmentExpression: enabledTypes }
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: enabledTypes;
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}
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//--------------------------------------------------------------------------
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// Helpers
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//--------------------------------------------------------------------------
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// eslint-disable-next-line jsdoc/require-description
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/**
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* @param {string} nodeType "AssignmentExpression" or "VariableDeclarator"
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* @param {string} destructuringType "array" or "object"
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* @returns {boolean} `true` if the destructuring type should be checked for the given node
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*/
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function shouldCheck(nodeType, destructuringType) {
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return normalizedOptions &&
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normalizedOptions[nodeType] &&
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normalizedOptions[nodeType][destructuringType];
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}
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/**
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* Determines if the given node is accessing an array index
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*
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* This is used to differentiate array index access from object property
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* access.
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* @param {ASTNode} node the node to evaluate
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* @returns {boolean} whether or not the node is an integer
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*/
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function isArrayIndexAccess(node) {
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return Number.isInteger(node.property.value);
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}
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/**
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* Report that the given node should use destructuring
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* @param {ASTNode} reportNode the node to report
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* @param {string} type the type of destructuring that should have been done
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* @param {Function|null} fix the fix function or null to pass to context.report
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* @returns {void}
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*/
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function report(reportNode, type, fix) {
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context.report({
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node: reportNode,
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messageId: "preferDestructuring",
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data: { type },
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fix
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});
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}
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/**
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* Determines if a node should be fixed into object destructuring
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*
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* The fixer only fixes the simplest case of object destructuring,
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* like: `let x = a.x`;
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*
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* Assignment expression is not fixed.
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* Array destructuring is not fixed.
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* Renamed property is not fixed.
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* @param {ASTNode} node the node to evaluate
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* @returns {boolean} whether or not the node should be fixed
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*/
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function shouldFix(node) {
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return node.type === "VariableDeclarator" &&
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node.id.type === "Identifier" &&
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node.init.type === "MemberExpression" &&
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!node.init.computed &&
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node.init.property.type === "Identifier" &&
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node.id.name === node.init.property.name;
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}
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/**
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* Fix a node into object destructuring.
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* This function only handles the simplest case of object destructuring,
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* see {@link shouldFix}.
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* @param {SourceCodeFixer} fixer the fixer object
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* @param {ASTNode} node the node to be fixed.
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* @returns {Object} a fix for the node
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*/
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function fixIntoObjectDestructuring(fixer, node) {
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const rightNode = node.init;
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const sourceCode = context.getSourceCode();
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// Don't fix if that would remove any comments. Only comments inside `rightNode.object` can be preserved.
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if (sourceCode.getCommentsInside(node).length > sourceCode.getCommentsInside(rightNode.object).length) {
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return null;
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}
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let objectText = sourceCode.getText(rightNode.object);
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if (astUtils.getPrecedence(rightNode.object) < PRECEDENCE_OF_ASSIGNMENT_EXPR) {
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objectText = `(${objectText})`;
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}
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return fixer.replaceText(
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node,
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`{${rightNode.property.name}} = ${objectText}`
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);
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}
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/**
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* Check that the `prefer-destructuring` rules are followed based on the
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* given left- and right-hand side of the assignment.
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*
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* Pulled out into a separate method so that VariableDeclarators and
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* AssignmentExpressions can share the same verification logic.
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* @param {ASTNode} leftNode the left-hand side of the assignment
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* @param {ASTNode} rightNode the right-hand side of the assignment
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* @param {ASTNode} reportNode the node to report the error on
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* @returns {void}
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*/
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function performCheck(leftNode, rightNode, reportNode) {
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if (rightNode.type !== "MemberExpression" || rightNode.object.type === "Super") {
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return;
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}
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if (isArrayIndexAccess(rightNode)) {
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if (shouldCheck(reportNode.type, "array")) {
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report(reportNode, "array", null);
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}
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return;
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}
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const fix = shouldFix(reportNode)
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? fixer => fixIntoObjectDestructuring(fixer, reportNode)
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: null;
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if (shouldCheck(reportNode.type, "object") && enforceForRenamedProperties) {
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report(reportNode, "object", fix);
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return;
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}
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if (shouldCheck(reportNode.type, "object")) {
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const property = rightNode.property;
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if (
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(property.type === "Literal" && leftNode.name === property.value) ||
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(property.type === "Identifier" && leftNode.name === property.name && !rightNode.computed)
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) {
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report(reportNode, "object", fix);
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}
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}
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}
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/**
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* Check if a given variable declarator is coming from an property access
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* that should be using destructuring instead
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* @param {ASTNode} node the variable declarator to check
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* @returns {void}
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*/
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function checkVariableDeclarator(node) {
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// Skip if variable is declared without assignment
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if (!node.init) {
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return;
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}
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// We only care about member expressions past this point
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if (node.init.type !== "MemberExpression") {
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return;
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}
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performCheck(node.id, node.init, node);
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}
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/**
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* Run the `prefer-destructuring` check on an AssignmentExpression
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* @param {ASTNode} node the AssignmentExpression node
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* @returns {void}
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*/
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function checkAssignmentExpression(node) {
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if (node.operator === "=") {
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performCheck(node.left, node.right, node);
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}
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}
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//--------------------------------------------------------------------------
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// Public
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//--------------------------------------------------------------------------
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return {
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VariableDeclarator: checkVariableDeclarator,
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AssignmentExpression: checkAssignmentExpression
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};
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}
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};
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