325 lines
8.7 KiB
JavaScript
325 lines
8.7 KiB
JavaScript
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'use strict';
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const {isCommaToken} = require('@eslint-community/eslint-utils');
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const {
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matches,
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newExpressionSelector,
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methodCallSelector,
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} = require('./selectors/index.js');
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const typedArray = require('./shared/typed-array.js');
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const {
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removeParentheses,
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fixSpaceAroundKeyword,
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addParenthesizesToReturnOrThrowExpression,
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} = require('./fix/index.js');
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const isOnSameLine = require('./utils/is-on-same-line.js');
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const {
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isParenthesized,
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} = require('./utils/parentheses.js');
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const {isNewExpression} = require('./ast/index.js');
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const SPREAD_IN_LIST = 'spread-in-list';
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const ITERABLE_TO_ARRAY = 'iterable-to-array';
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const ITERABLE_TO_ARRAY_IN_FOR_OF = 'iterable-to-array-in-for-of';
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const ITERABLE_TO_ARRAY_IN_YIELD_STAR = 'iterable-to-array-in-yield-star';
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const CLONE_ARRAY = 'clone-array';
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const messages = {
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[SPREAD_IN_LIST]: 'Spread an {{argumentType}} literal in {{parentDescription}} is unnecessary.',
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[ITERABLE_TO_ARRAY]: '`{{parentDescription}}` accepts iterable as argument, it\'s unnecessary to convert to an array.',
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[ITERABLE_TO_ARRAY_IN_FOR_OF]: '`for…of` can iterate over iterable, it\'s unnecessary to convert to an array.',
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[ITERABLE_TO_ARRAY_IN_YIELD_STAR]: '`yield*` can delegate iterable, it\'s unnecessary to convert to an array.',
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[CLONE_ARRAY]: 'Unnecessarily cloning an array.',
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};
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const uselessSpreadInListSelector = matches([
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'ArrayExpression > SpreadElement.elements > ArrayExpression.argument',
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'ObjectExpression > SpreadElement.properties > ObjectExpression.argument',
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'CallExpression > SpreadElement.arguments > ArrayExpression.argument',
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'NewExpression > SpreadElement.arguments > ArrayExpression.argument',
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]);
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const singleArraySpreadSelector = [
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'ArrayExpression',
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'[elements.length=1]',
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'[elements.0.type="SpreadElement"]',
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].join('');
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const uselessIterableToArraySelector = matches([
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[
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matches([
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newExpressionSelector({names: ['Map', 'WeakMap', 'Set', 'WeakSet'], argumentsLength: 1}),
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newExpressionSelector({names: typedArray, minimumArguments: 1}),
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methodCallSelector({
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object: 'Promise',
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methods: ['all', 'allSettled', 'any', 'race'],
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argumentsLength: 1,
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}),
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methodCallSelector({
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objects: ['Array', ...typedArray],
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method: 'from',
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argumentsLength: 1,
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}),
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methodCallSelector({object: 'Object', method: 'fromEntries', argumentsLength: 1}),
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]),
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' > ',
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`${singleArraySpreadSelector}.arguments:first-child`,
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].join(''),
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`ForOfStatement > ${singleArraySpreadSelector}.right`,
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`YieldExpression[delegate=true] > ${singleArraySpreadSelector}.argument`,
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]);
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const uselessArrayCloneSelector = [
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`${singleArraySpreadSelector} > .elements:first-child > .argument`,
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matches([
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// Array methods returns a new array
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methodCallSelector([
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'concat',
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'copyWithin',
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'filter',
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'flat',
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'flatMap',
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'map',
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'slice',
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'splice',
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'toReversed',
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'toSorted',
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'toSpliced',
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'with',
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]),
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// `String#split()`
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methodCallSelector('split'),
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// `Object.keys()` and `Object.values()`
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methodCallSelector({object: 'Object', methods: ['keys', 'values'], argumentsLength: 1}),
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// `await Promise.all()` and `await Promise.allSettled`
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[
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'AwaitExpression',
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methodCallSelector({
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object: 'Promise',
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methods: ['all', 'allSettled'],
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argumentsLength: 1,
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path: 'argument',
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}),
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].join(''),
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// `Array.from()`, `Array.of()`
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methodCallSelector({object: 'Array', methods: ['from', 'of']}),
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// `new Array()`
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newExpressionSelector('Array'),
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]),
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].join('');
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const parentDescriptions = {
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ArrayExpression: 'array literal',
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ObjectExpression: 'object literal',
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CallExpression: 'arguments',
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NewExpression: 'arguments',
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};
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function getCommaTokens(arrayExpression, sourceCode) {
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let startToken = sourceCode.getFirstToken(arrayExpression);
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return arrayExpression.elements.map((element, index, elements) => {
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if (index === elements.length - 1) {
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const penultimateToken = sourceCode.getLastToken(arrayExpression, {skip: 1});
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if (isCommaToken(penultimateToken)) {
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return penultimateToken;
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}
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return;
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}
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const commaToken = sourceCode.getTokenAfter(element || startToken, isCommaToken);
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startToken = commaToken;
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return commaToken;
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});
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}
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function * unwrapSingleArraySpread(fixer, arrayExpression, sourceCode) {
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const [
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openingBracketToken,
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spreadToken,
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thirdToken,
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] = sourceCode.getFirstTokens(arrayExpression, 3);
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// `[...value]`
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// ^
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yield fixer.remove(openingBracketToken);
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// `[...value]`
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// ^^^
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yield fixer.remove(spreadToken);
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const [
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commaToken,
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closingBracketToken,
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] = sourceCode.getLastTokens(arrayExpression, 2);
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// `[...value]`
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// ^
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yield fixer.remove(closingBracketToken);
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// `[...value,]`
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// ^
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if (isCommaToken(commaToken)) {
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yield fixer.remove(commaToken);
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}
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/*
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```js
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function foo() {
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return [
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...value,
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];
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}
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```
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*/
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const {parent} = arrayExpression;
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if (
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(parent.type === 'ReturnStatement' || parent.type === 'ThrowStatement')
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&& parent.argument === arrayExpression
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&& !isOnSameLine(openingBracketToken, thirdToken)
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&& !isParenthesized(arrayExpression, sourceCode)
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) {
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yield * addParenthesizesToReturnOrThrowExpression(fixer, parent, sourceCode);
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return;
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}
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yield * fixSpaceAroundKeyword(fixer, arrayExpression, sourceCode);
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}
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/** @param {import('eslint').Rule.RuleContext} context */
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const create = context => {
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const sourceCode = context.getSourceCode();
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return {
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[uselessSpreadInListSelector](spreadObject) {
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const spreadElement = spreadObject.parent;
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const spreadToken = sourceCode.getFirstToken(spreadElement);
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const parentType = spreadElement.parent.type;
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return {
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node: spreadToken,
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messageId: SPREAD_IN_LIST,
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data: {
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argumentType: spreadObject.type === 'ArrayExpression' ? 'array' : 'object',
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parentDescription: parentDescriptions[parentType],
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},
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/** @param {import('eslint').Rule.RuleFixer} fixer */
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* fix(fixer) {
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// `[...[foo]]`
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// ^^^
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yield fixer.remove(spreadToken);
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// `[...(( [foo] ))]`
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// ^^ ^^
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yield * removeParentheses(spreadObject, fixer, sourceCode);
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// `[...[foo]]`
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// ^
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const firstToken = sourceCode.getFirstToken(spreadObject);
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yield fixer.remove(firstToken);
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const [
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penultimateToken,
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lastToken,
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] = sourceCode.getLastTokens(spreadObject, 2);
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// `[...[foo]]`
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// ^
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yield fixer.remove(lastToken);
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// `[...[foo,]]`
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// ^
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if (isCommaToken(penultimateToken)) {
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yield fixer.remove(penultimateToken);
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}
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if (parentType !== 'CallExpression' && parentType !== 'NewExpression') {
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return;
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}
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const commaTokens = getCommaTokens(spreadObject, sourceCode);
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for (const [index, commaToken] of commaTokens.entries()) {
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if (spreadObject.elements[index]) {
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continue;
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}
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// `call(...[foo, , bar])`
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// ^ Replace holes with `undefined`
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yield fixer.insertTextBefore(commaToken, 'undefined');
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}
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},
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};
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},
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[uselessIterableToArraySelector](arrayExpression) {
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const {parent} = arrayExpression;
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let parentDescription = '';
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let messageId = ITERABLE_TO_ARRAY;
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switch (parent.type) {
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case 'ForOfStatement': {
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messageId = ITERABLE_TO_ARRAY_IN_FOR_OF;
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break;
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}
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case 'YieldExpression': {
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messageId = ITERABLE_TO_ARRAY_IN_YIELD_STAR;
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break;
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}
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case 'NewExpression': {
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parentDescription = `new ${parent.callee.name}(…)`;
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break;
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}
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case 'CallExpression': {
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parentDescription = `${parent.callee.object.name}.${parent.callee.property.name}(…)`;
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break;
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}
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// No default
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}
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return {
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node: arrayExpression,
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messageId,
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data: {parentDescription},
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fix: fixer => unwrapSingleArraySpread(fixer, arrayExpression, sourceCode),
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};
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},
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[uselessArrayCloneSelector](node) {
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const arrayExpression = node.parent.parent;
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const problem = {
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node: arrayExpression,
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messageId: CLONE_ARRAY,
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};
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if (
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// `[...new Array(1)]` -> `new Array(1)` is not safe to fix since there are holes
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isNewExpression(node, {name: 'Array'})
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// `[...foo.slice(1)]` -> `foo.slice(1)` is not safe to fix since `foo` can be a string
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node.type === 'CallExpression'
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&& node.callee.type === 'MemberExpression'
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&& node.callee.property.type === 'Identifier'
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&& node.callee.property.name === 'slice'
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)
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) {
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return problem;
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}
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return Object.assign(problem, {
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fix: fixer => unwrapSingleArraySpread(fixer, arrayExpression, sourceCode),
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});
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},
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};
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};
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/** @type {import('eslint').Rule.RuleModule} */
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module.exports = {
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create,
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meta: {
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type: 'suggestion',
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docs: {
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description: 'Disallow unnecessary spread.',
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},
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fixable: 'code',
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messages,
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},
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};
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