266 lines
9.0 KiB
JavaScript
266 lines
9.0 KiB
JavaScript
/**
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* @fileoverview Prefers object spread property over Object.assign
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* @author Sharmila Jesupaul
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* See LICENSE file in root directory for full license.
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*/
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"use strict";
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const { CALL, ReferenceTracker } = require("eslint-utils");
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const {
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isCommaToken,
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isOpeningParenToken,
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isClosingParenToken,
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isParenthesised
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} = require("./utils/ast-utils");
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const ANY_SPACE = /\s/u;
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/**
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* Helper that checks if the Object.assign call has array spread
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* @param {ASTNode} node The node that the rule warns on
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* @returns {boolean} - Returns true if the Object.assign call has array spread
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*/
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function hasArraySpread(node) {
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return node.arguments.some(arg => arg.type === "SpreadElement");
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}
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/**
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* Helper that checks if the node needs parentheses to be valid JS.
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* The default is to wrap the node in parentheses to avoid parsing errors.
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* @param {ASTNode} node The node that the rule warns on
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* @param {Object} sourceCode in context sourcecode object
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* @returns {boolean} - Returns true if the node needs parentheses
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*/
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function needsParens(node, sourceCode) {
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const parent = node.parent;
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switch (parent.type) {
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case "VariableDeclarator":
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case "ArrayExpression":
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case "ReturnStatement":
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case "CallExpression":
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case "Property":
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return false;
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case "AssignmentExpression":
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return parent.left === node && !isParenthesised(sourceCode, node);
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default:
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return !isParenthesised(sourceCode, node);
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}
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}
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/**
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* Determines if an argument needs parentheses. The default is to not add parens.
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* @param {ASTNode} node The node to be checked.
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* @param {Object} sourceCode in context sourcecode object
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* @returns {boolean} True if the node needs parentheses
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*/
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function argNeedsParens(node, sourceCode) {
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switch (node.type) {
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case "AssignmentExpression":
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case "ArrowFunctionExpression":
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case "ConditionalExpression":
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return !isParenthesised(sourceCode, node);
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default:
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return false;
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}
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}
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/**
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* Get the parenthesis tokens of a given ObjectExpression node.
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* This incldues the braces of the object literal and enclosing parentheses.
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* @param {ASTNode} node The node to get.
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* @param {Token} leftArgumentListParen The opening paren token of the argument list.
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* @param {SourceCode} sourceCode The source code object to get tokens.
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* @returns {Token[]} The parenthesis tokens of the node. This is sorted by the location.
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*/
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function getParenTokens(node, leftArgumentListParen, sourceCode) {
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const parens = [sourceCode.getFirstToken(node), sourceCode.getLastToken(node)];
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let leftNext = sourceCode.getTokenBefore(node);
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let rightNext = sourceCode.getTokenAfter(node);
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// Note: don't include the parens of the argument list.
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while (
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leftNext &&
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rightNext &&
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leftNext.range[0] > leftArgumentListParen.range[0] &&
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isOpeningParenToken(leftNext) &&
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isClosingParenToken(rightNext)
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) {
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parens.push(leftNext, rightNext);
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leftNext = sourceCode.getTokenBefore(leftNext);
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rightNext = sourceCode.getTokenAfter(rightNext);
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}
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return parens.sort((a, b) => a.range[0] - b.range[0]);
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}
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/**
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* Get the range of a given token and around whitespaces.
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* @param {Token} token The token to get range.
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* @param {SourceCode} sourceCode The source code object to get tokens.
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* @returns {number} The end of the range of the token and around whitespaces.
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*/
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function getStartWithSpaces(token, sourceCode) {
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const text = sourceCode.text;
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let start = token.range[0];
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// If the previous token is a line comment then skip this step to avoid commenting this token out.
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{
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const prevToken = sourceCode.getTokenBefore(token, { includeComments: true });
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if (prevToken && prevToken.type === "Line") {
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return start;
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}
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}
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// Detect spaces before the token.
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while (ANY_SPACE.test(text[start - 1] || "")) {
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start -= 1;
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}
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return start;
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}
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/**
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* Get the range of a given token and around whitespaces.
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* @param {Token} token The token to get range.
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* @param {SourceCode} sourceCode The source code object to get tokens.
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* @returns {number} The start of the range of the token and around whitespaces.
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*/
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function getEndWithSpaces(token, sourceCode) {
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const text = sourceCode.text;
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let end = token.range[1];
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// Detect spaces after the token.
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while (ANY_SPACE.test(text[end] || "")) {
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end += 1;
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}
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return end;
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}
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/**
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* Autofixes the Object.assign call to use an object spread instead.
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* @param {ASTNode|null} node The node that the rule warns on, i.e. the Object.assign call
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* @param {string} sourceCode sourceCode of the Object.assign call
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* @returns {Function} autofixer - replaces the Object.assign with a spread object.
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*/
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function defineFixer(node, sourceCode) {
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return function *(fixer) {
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const leftParen = sourceCode.getTokenAfter(node.callee, isOpeningParenToken);
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const rightParen = sourceCode.getLastToken(node);
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// Remove the callee `Object.assign`
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yield fixer.remove(node.callee);
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// Replace the parens of argument list to braces.
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if (needsParens(node, sourceCode)) {
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yield fixer.replaceText(leftParen, "({");
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yield fixer.replaceText(rightParen, "})");
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} else {
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yield fixer.replaceText(leftParen, "{");
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yield fixer.replaceText(rightParen, "}");
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}
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// Process arguments.
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for (const argNode of node.arguments) {
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const innerParens = getParenTokens(argNode, leftParen, sourceCode);
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const left = innerParens.shift();
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const right = innerParens.pop();
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if (argNode.type === "ObjectExpression") {
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const maybeTrailingComma = sourceCode.getLastToken(argNode, 1);
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const maybeArgumentComma = sourceCode.getTokenAfter(right);
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/*
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* Make bare this object literal.
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* And remove spaces inside of the braces for better formatting.
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*/
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for (const innerParen of innerParens) {
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yield fixer.remove(innerParen);
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}
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const leftRange = [left.range[0], getEndWithSpaces(left, sourceCode)];
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const rightRange = [
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Math.max(getStartWithSpaces(right, sourceCode), leftRange[1]), // Ensure ranges don't overlap
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right.range[1]
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];
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yield fixer.removeRange(leftRange);
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yield fixer.removeRange(rightRange);
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// Remove the comma of this argument if it's duplication.
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if (
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(argNode.properties.length === 0 || isCommaToken(maybeTrailingComma)) &&
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isCommaToken(maybeArgumentComma)
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) {
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yield fixer.remove(maybeArgumentComma);
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}
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} else {
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// Make spread.
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if (argNeedsParens(argNode, sourceCode)) {
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yield fixer.insertTextBefore(left, "...(");
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yield fixer.insertTextAfter(right, ")");
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} else {
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yield fixer.insertTextBefore(left, "...");
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}
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}
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}
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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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docs: {
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description:
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"disallow using Object.assign with an object literal as the first argument and prefer the use of object spread instead.",
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category: "Stylistic Issues",
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recommended: false,
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url: "https://eslint.org/docs/rules/prefer-object-spread"
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},
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schema: [],
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fixable: "code",
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messages: {
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useSpreadMessage: "Use an object spread instead of `Object.assign` eg: `{ ...foo }`.",
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useLiteralMessage: "Use an object literal instead of `Object.assign`. eg: `{ foo: bar }`."
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}
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},
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create(context) {
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const sourceCode = context.getSourceCode();
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return {
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Program() {
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const scope = context.getScope();
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const tracker = new ReferenceTracker(scope);
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const trackMap = {
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Object: {
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assign: { [CALL]: true }
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}
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};
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// Iterate all calls of `Object.assign` (only of the global variable `Object`).
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for (const { node } of tracker.iterateGlobalReferences(trackMap)) {
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if (
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node.arguments.length >= 1 &&
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node.arguments[0].type === "ObjectExpression" &&
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!hasArraySpread(node)
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) {
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const messageId = node.arguments.length === 1
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? "useLiteralMessage"
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: "useSpreadMessage";
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const fix = defineFixer(node, sourceCode);
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context.report({ node, messageId, fix });
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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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