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Le Viet
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/**
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* @fileoverview Rule to require braces in arrow function body.
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* @author Alberto Rodríguez
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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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// 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 braces around arrow function bodies",
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category: "ECMAScript 6",
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recommended: false,
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url: "https://eslint.org/docs/rules/arrow-body-style"
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},
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schema: {
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anyOf: [
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{
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type: "array",
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items: [
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{
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enum: ["always", "never"]
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}
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],
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minItems: 0,
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maxItems: 1
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},
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{
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type: "array",
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items: [
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{
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enum: ["as-needed"]
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},
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{
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type: "object",
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properties: {
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requireReturnForObjectLiteral: { type: "boolean" }
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},
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additionalProperties: false
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}
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],
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minItems: 0,
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maxItems: 2
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}
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]
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},
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fixable: "code",
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messages: {
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unexpectedOtherBlock: "Unexpected block statement surrounding arrow body.",
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unexpectedEmptyBlock: "Unexpected block statement surrounding arrow body; put a value of `undefined` immediately after the `=>`.",
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unexpectedObjectBlock: "Unexpected block statement surrounding arrow body; parenthesize the returned value and move it immediately after the `=>`.",
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unexpectedSingleBlock: "Unexpected block statement surrounding arrow body; move the returned value immediately after the `=>`.",
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expectedBlock: "Expected block statement surrounding arrow body."
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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 always = options[0] === "always";
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const asNeeded = !options[0] || options[0] === "as-needed";
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const never = options[0] === "never";
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const requireReturnForObjectLiteral = options[1] && options[1].requireReturnForObjectLiteral;
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const sourceCode = context.getSourceCode();
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/**
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* Checks whether the given node has ASI problem or not.
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* @param {Token} token The token to check.
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* @returns {boolean} `true` if it changes semantics if `;` or `}` followed by the token are removed.
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*/
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function hasASIProblem(token) {
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return token && token.type === "Punctuator" && /^[([/`+-]/u.test(token.value);
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}
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/**
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* Gets the closing parenthesis which is the pair of the given opening parenthesis.
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* @param {Token} token The opening parenthesis token to get.
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* @returns {Token} The found closing parenthesis token.
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*/
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function findClosingParen(token) {
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let node = sourceCode.getNodeByRangeIndex(token.range[1]);
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while (!astUtils.isParenthesised(sourceCode, node)) {
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node = node.parent;
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}
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return sourceCode.getTokenAfter(node);
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}
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/**
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* Determines whether a arrow function body needs braces
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* @param {ASTNode} node The arrow function node.
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* @returns {void}
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*/
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function validate(node) {
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const arrowBody = node.body;
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if (arrowBody.type === "BlockStatement") {
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const blockBody = arrowBody.body;
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if (blockBody.length !== 1 && !never) {
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return;
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}
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if (asNeeded && requireReturnForObjectLiteral && blockBody[0].type === "ReturnStatement" &&
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blockBody[0].argument && blockBody[0].argument.type === "ObjectExpression") {
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return;
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}
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if (never || asNeeded && blockBody[0].type === "ReturnStatement") {
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let messageId;
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if (blockBody.length === 0) {
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messageId = "unexpectedEmptyBlock";
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} else if (blockBody.length > 1) {
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messageId = "unexpectedOtherBlock";
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} else if (blockBody[0].argument === null) {
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messageId = "unexpectedSingleBlock";
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} else if (astUtils.isOpeningBraceToken(sourceCode.getFirstToken(blockBody[0], { skip: 1 }))) {
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messageId = "unexpectedObjectBlock";
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} else {
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messageId = "unexpectedSingleBlock";
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}
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context.report({
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node,
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loc: arrowBody.loc.start,
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messageId,
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fix(fixer) {
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const fixes = [];
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if (blockBody.length !== 1 ||
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blockBody[0].type !== "ReturnStatement" ||
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!blockBody[0].argument ||
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hasASIProblem(sourceCode.getTokenAfter(arrowBody))
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) {
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return fixes;
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}
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const openingBrace = sourceCode.getFirstToken(arrowBody);
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const closingBrace = sourceCode.getLastToken(arrowBody);
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const firstValueToken = sourceCode.getFirstToken(blockBody[0], 1);
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const lastValueToken = sourceCode.getLastToken(blockBody[0]);
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const commentsExist =
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sourceCode.commentsExistBetween(openingBrace, firstValueToken) ||
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sourceCode.commentsExistBetween(lastValueToken, closingBrace);
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/*
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* Remove tokens around the return value.
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* If comments don't exist, remove extra spaces as well.
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*/
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if (commentsExist) {
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fixes.push(
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fixer.remove(openingBrace),
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fixer.remove(closingBrace),
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fixer.remove(sourceCode.getTokenAfter(openingBrace)) // return keyword
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);
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} else {
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fixes.push(
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fixer.removeRange([openingBrace.range[0], firstValueToken.range[0]]),
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fixer.removeRange([lastValueToken.range[1], closingBrace.range[1]])
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);
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}
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/*
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* If the first token of the reutrn value is `{` or the return value is a sequence expression,
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* enclose the return value by parentheses to avoid syntax error.
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*/
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if (astUtils.isOpeningBraceToken(firstValueToken) || blockBody[0].argument.type === "SequenceExpression") {
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fixes.push(
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fixer.insertTextBefore(firstValueToken, "("),
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fixer.insertTextAfter(lastValueToken, ")")
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);
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}
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/*
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* If the last token of the return statement is semicolon, remove it.
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* Non-block arrow body is an expression, not a statement.
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*/
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if (astUtils.isSemicolonToken(lastValueToken)) {
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fixes.push(fixer.remove(lastValueToken));
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}
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return fixes;
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}
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});
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}
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} else {
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if (always || (asNeeded && requireReturnForObjectLiteral && arrowBody.type === "ObjectExpression")) {
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context.report({
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node,
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loc: arrowBody.loc.start,
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messageId: "expectedBlock",
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fix(fixer) {
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const fixes = [];
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const arrowToken = sourceCode.getTokenBefore(arrowBody, astUtils.isArrowToken);
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const firstBodyToken = sourceCode.getTokenAfter(arrowToken);
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const lastBodyToken = sourceCode.getLastToken(node);
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const isParenthesisedObjectLiteral =
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astUtils.isOpeningParenToken(firstBodyToken) &&
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astUtils.isOpeningBraceToken(sourceCode.getTokenAfter(firstBodyToken));
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// Wrap the value by a block and a return statement.
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fixes.push(
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fixer.insertTextBefore(firstBodyToken, "{return "),
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fixer.insertTextAfter(lastBodyToken, "}")
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);
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// If the value is object literal, remove parentheses which were forced by syntax.
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if (isParenthesisedObjectLiteral) {
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fixes.push(
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fixer.remove(firstBodyToken),
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fixer.remove(findClosingParen(firstBodyToken))
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);
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}
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return fixes;
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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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"ArrowFunctionExpression:exit": validate
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};
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}
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};
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