2 * @fileoverview Rule to require braces in arrow function body.
3 * @author Alberto RodrÃguez
7 //------------------------------------------------------------------------------
9 //------------------------------------------------------------------------------
11 const astUtils
= require("./utils/ast-utils");
13 //------------------------------------------------------------------------------
15 //------------------------------------------------------------------------------
22 description
: "require braces around arrow function bodies",
23 category
: "ECMAScript 6",
25 url
: "https://eslint.org/docs/rules/arrow-body-style"
34 enum: ["always", "never"]
49 requireReturnForObjectLiteral
: { type
: "boolean" }
51 additionalProperties
: false
63 unexpectedOtherBlock
: "Unexpected block statement surrounding arrow body.",
64 unexpectedEmptyBlock
: "Unexpected block statement surrounding arrow body; put a value of `undefined` immediately after the `=>`.",
65 unexpectedObjectBlock
: "Unexpected block statement surrounding arrow body; parenthesize the returned value and move it immediately after the `=>`.",
66 unexpectedSingleBlock
: "Unexpected block statement surrounding arrow body; move the returned value immediately after the `=>`.",
67 expectedBlock
: "Expected block statement surrounding arrow body."
72 const options
= context
.options
;
73 const always
= options
[0] === "always";
74 const asNeeded
= !options
[0] || options
[0] === "as-needed";
75 const never
= options
[0] === "never";
76 const requireReturnForObjectLiteral
= options
[1] && options
[1].requireReturnForObjectLiteral
;
77 const sourceCode
= context
.getSourceCode();
81 * Checks whether the given node has ASI problem or not.
82 * @param {Token} token The token to check.
83 * @returns {boolean} `true` if it changes semantics if `;` or `}` followed by the token are removed.
85 function hasASIProblem(token
) {
86 return token
&& token
.type
=== "Punctuator" && /^[([/`+-]/u.test(token.value);
90 * Gets the closing parenthesis which is the pair of the given opening parenthesis.
91 * @param {Token} token The opening parenthesis token to get.
92 * @returns {Token} The found closing parenthesis token.
94 function findClosingParen(token) {
95 let node = sourceCode.getNodeByRangeIndex(token.range[0]);
97 while (!astUtils.isParenthesised(sourceCode, node)) {
100 return sourceCode.getTokenAfter(node);
104 * Check whether the node is inside of a for loop's init
105 * @param {ASTNode} node node is inside for loop
106 * @returns {boolean} `true` if the node is inside of a for loop, else `false`
108 function isInsideForLoopInitializer(node) {
109 if (node && node.parent) {
110 if (node.parent.type === "ForStatement" && node.parent.init === node) {
113 return isInsideForLoopInitializer(node.parent);
119 * Determines whether a arrow function body needs braces
120 * @param {ASTNode} node The arrow function node.
123 function validate(node) {
124 const arrowBody = node.body;
126 if (arrowBody.type === "BlockStatement") {
127 const blockBody = arrowBody.body;
129 if (blockBody.length !== 1 && !never) {
133 if (asNeeded && requireReturnForObjectLiteral && blockBody[0].type === "ReturnStatement" &&
134 blockBody[0].argument && blockBody[0].argument.type === "ObjectExpression") {
138 if (never || asNeeded && blockBody[0].type === "ReturnStatement") {
141 if (blockBody.length === 0) {
142 messageId = "unexpectedEmptyBlock";
143 } else if (blockBody.length > 1) {
144 messageId = "unexpectedOtherBlock";
145 } else if (blockBody[0].argument === null) {
146 messageId = "unexpectedSingleBlock";
147 } else if (astUtils.isOpeningBraceToken(sourceCode.getFirstToken(blockBody[0], { skip: 1 }))) {
148 messageId = "unexpectedObjectBlock";
150 messageId = "unexpectedSingleBlock";
160 if (blockBody.length !== 1 ||
161 blockBody[0].type !== "ReturnStatement" ||
162 !blockBody[0].argument ||
163 hasASIProblem(sourceCode.getTokenAfter(arrowBody))
168 const openingBrace = sourceCode.getFirstToken(arrowBody);
169 const closingBrace = sourceCode.getLastToken(arrowBody);
170 const firstValueToken = sourceCode.getFirstToken(blockBody[0], 1);
171 const lastValueToken = sourceCode.getLastToken(blockBody[0]);
172 const commentsExist =
173 sourceCode.commentsExistBetween(openingBrace, firstValueToken) ||
174 sourceCode.commentsExistBetween(lastValueToken, closingBrace);
177 * Remove tokens around the return value.
178 * If comments don't exist, remove extra spaces as well.
182 fixer.remove(openingBrace),
183 fixer.remove(closingBrace),
184 fixer.remove(sourceCode.getTokenAfter(openingBrace)) // return keyword
188 fixer.removeRange([openingBrace.range[0], firstValueToken.range[0]]),
189 fixer.removeRange([lastValueToken.range[1], closingBrace.range[1]])
194 * If the first token of the return value is `{` or the return value is a sequence expression,
195 * enclose the return value by parentheses to avoid syntax error.
197 if (astUtils.isOpeningBraceToken(firstValueToken) || blockBody[0].argument.type === "SequenceExpression" || (funcInfo.hasInOperator && isInsideForLoopInitializer(node))) {
198 if (!astUtils.isParenthesised(sourceCode, blockBody[0].argument)) {
200 fixer.insertTextBefore(firstValueToken, "("),
201 fixer.insertTextAfter(lastValueToken, ")")
207 * If the last token of the return statement is semicolon, remove it.
208 * Non-block arrow body is an expression, not a statement.
210 if (astUtils.isSemicolonToken(lastValueToken)) {
211 fixes.push(fixer.remove(lastValueToken));
219 if (always || (asNeeded && requireReturnForObjectLiteral && arrowBody.type === "ObjectExpression")) {
223 messageId: "expectedBlock",
226 const arrowToken = sourceCode.getTokenBefore(arrowBody, astUtils.isArrowToken);
227 const [firstTokenAfterArrow, secondTokenAfterArrow] = sourceCode.getTokensAfter(arrowToken, { count: 2 });
228 const lastToken = sourceCode.getLastToken(node);
229 const isParenthesisedObjectLiteral =
230 astUtils.isOpeningParenToken(firstTokenAfterArrow) &&
231 astUtils.isOpeningBraceToken(secondTokenAfterArrow);
233 // If the value is object literal, remove parentheses which were forced by syntax.
234 if (isParenthesisedObjectLiteral) {
235 const openingParenToken = firstTokenAfterArrow;
236 const openingBraceToken = secondTokenAfterArrow;
238 if (astUtils.isTokenOnSameLine(openingParenToken, openingBraceToken)) {
239 fixes.push(fixer.replaceText(openingParenToken, "{return "));
244 fixer.replaceText(openingParenToken, "{"),
245 fixer.insertTextBefore(openingBraceToken, "return ")
249 // Closing paren for the object doesn't have to be lastToken, e.g.: () => ({}).foo()
250 fixes.push(fixer.remove(findClosingParen(openingBraceToken)));
251 fixes.push(fixer.insertTextAfter(lastToken, "}"));
254 fixes.push(fixer.insertTextBefore(firstTokenAfterArrow, "{return "));
255 fixes.push(fixer.insertTextAfter(lastToken, "}"));
266 "BinaryExpression[operator='in']"() {
270 info.hasInOperator = true;
274 ArrowFunctionExpression() {
280 "ArrowFunctionExpression:exit"(node) {
282 funcInfo = funcInfo.upper;