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qwen/nodejs/node_modules/eslint/lib/rules/arrow-body-style.js

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+/**
+ * @fileoverview Rule to require braces in arrow function body.
+ * @author Alberto Rodríguez
+ */
+"use strict";
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+const astUtils = require("./utils/ast-utils");
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+/** @type {import('../shared/types').Rule} */
+module.exports = {
+    meta: {
+        type: "suggestion",
+
+        docs: {
+            description: "Require braces around arrow function bodies",
+            recommended: false,
+            url: "https://eslint.org/docs/latest/rules/arrow-body-style"
+        },
+
+        schema: {
+            anyOf: [
+                {
+                    type: "array",
+                    items: [
+                        {
+                            enum: ["always", "never"]
+                        }
+                    ],
+                    minItems: 0,
+                    maxItems: 1
+                },
+                {
+                    type: "array",
+                    items: [
+                        {
+                            enum: ["as-needed"]
+                        },
+                        {
+                            type: "object",
+                            properties: {
+                                requireReturnForObjectLiteral: { type: "boolean" }
+                            },
+                            additionalProperties: false
+                        }
+                    ],
+                    minItems: 0,
+                    maxItems: 2
+                }
+            ]
+        },
+
+        fixable: "code",
+
+        messages: {
+            unexpectedOtherBlock: "Unexpected block statement surrounding arrow body.",
+            unexpectedEmptyBlock: "Unexpected block statement surrounding arrow body; put a value of `undefined` immediately after the `=>`.",
+            unexpectedObjectBlock: "Unexpected block statement surrounding arrow body; parenthesize the returned value and move it immediately after the `=>`.",
+            unexpectedSingleBlock: "Unexpected block statement surrounding arrow body; move the returned value immediately after the `=>`.",
+            expectedBlock: "Expected block statement surrounding arrow body."
+        }
+    },
+
+    create(context) {
+        const options = context.options;
+        const always = options[0] === "always";
+        const asNeeded = !options[0] || options[0] === "as-needed";
+        const never = options[0] === "never";
+        const requireReturnForObjectLiteral = options[1] && options[1].requireReturnForObjectLiteral;
+        const sourceCode = context.sourceCode;
+        let funcInfo = null;
+
+        /**
+         * Checks whether the given node has ASI problem or not.
+         * @param {Token} token The token to check.
+         * @returns {boolean} `true` if it changes semantics if `;` or `}` followed by the token are removed.
+         */
+        function hasASIProblem(token) {
+            return token && token.type === "Punctuator" && /^[([/`+-]/u.test(token.value);
+        }
+
+        /**
+         * Gets the closing parenthesis by the given node.
+         * @param {ASTNode} node first node after an opening parenthesis.
+         * @returns {Token} The found closing parenthesis token.
+         */
+        function findClosingParen(node) {
+            let nodeToCheck = node;
+
+            while (!astUtils.isParenthesised(sourceCode, nodeToCheck)) {
+                nodeToCheck = nodeToCheck.parent;
+            }
+            return sourceCode.getTokenAfter(nodeToCheck);
+        }
+
+        /**
+         * Check whether the node is inside of a for loop's init
+         * @param {ASTNode} node node is inside for loop
+         * @returns {boolean} `true` if the node is inside of a for loop, else `false`
+         */
+        function isInsideForLoopInitializer(node) {
+            if (node && node.parent) {
+                if (node.parent.type === "ForStatement" && node.parent.init === node) {
+                    return true;
+                }
+                return isInsideForLoopInitializer(node.parent);
+            }
+            return false;
+        }
+
+        /**
+         * Determines whether a arrow function body needs braces
+         * @param {ASTNode} node The arrow function node.
+         * @returns {void}
+         */
+        function validate(node) {
+            const arrowBody = node.body;
+
+            if (arrowBody.type === "BlockStatement") {
+                const blockBody = arrowBody.body;
+
+                if (blockBody.length !== 1 && !never) {
+                    return;
+                }
+
+                if (asNeeded && requireReturnForObjectLiteral && blockBody[0].type === "ReturnStatement" &&
+                    blockBody[0].argument && blockBody[0].argument.type === "ObjectExpression") {
+                    return;
+                }
+
+                if (never || asNeeded && blockBody[0].type === "ReturnStatement") {
+                    let messageId;
+
+                    if (blockBody.length === 0) {
+                        messageId = "unexpectedEmptyBlock";
+                    } else if (blockBody.length > 1) {
+                        messageId = "unexpectedOtherBlock";
+                    } else if (blockBody[0].argument === null) {
+                        messageId = "unexpectedSingleBlock";
+                    } else if (astUtils.isOpeningBraceToken(sourceCode.getFirstToken(blockBody[0], { skip: 1 }))) {
+                        messageId = "unexpectedObjectBlock";
+                    } else {
+                        messageId = "unexpectedSingleBlock";
+                    }
+
+                    context.report({
+                        node,
+                        loc: arrowBody.loc,
+                        messageId,
+                        fix(fixer) {
+                            const fixes = [];
+
+                            if (blockBody.length !== 1 ||
+                                blockBody[0].type !== "ReturnStatement" ||
+                                !blockBody[0].argument ||
+                                hasASIProblem(sourceCode.getTokenAfter(arrowBody))
+                            ) {
+                                return fixes;
+                            }
+
+                            const openingBrace = sourceCode.getFirstToken(arrowBody);
+                            const closingBrace = sourceCode.getLastToken(arrowBody);
+                            const firstValueToken = sourceCode.getFirstToken(blockBody[0], 1);
+                            const lastValueToken = sourceCode.getLastToken(blockBody[0]);
+                            const commentsExist =
+                                sourceCode.commentsExistBetween(openingBrace, firstValueToken) ||
+                                sourceCode.commentsExistBetween(lastValueToken, closingBrace);
+
+                            /*
+                             * Remove tokens around the return value.
+                             * If comments don't exist, remove extra spaces as well.
+                             */
+                            if (commentsExist) {
+                                fixes.push(
+                                    fixer.remove(openingBrace),
+                                    fixer.remove(closingBrace),
+                                    fixer.remove(sourceCode.getTokenAfter(openingBrace)) // return keyword
+                                );
+                            } else {
+                                fixes.push(
+                                    fixer.removeRange([openingBrace.range[0], firstValueToken.range[0]]),
+                                    fixer.removeRange([lastValueToken.range[1], closingBrace.range[1]])
+                                );
+                            }
+
+                            /*
+                             * If the first token of the return value is `{` or the return value is a sequence expression,
+                             * enclose the return value by parentheses to avoid syntax error.
+                             */
+                            if (astUtils.isOpeningBraceToken(firstValueToken) || blockBody[0].argument.type === "SequenceExpression" || (funcInfo.hasInOperator && isInsideForLoopInitializer(node))) {
+                                if (!astUtils.isParenthesised(sourceCode, blockBody[0].argument)) {
+                                    fixes.push(
+                                        fixer.insertTextBefore(firstValueToken, "("),
+                                        fixer.insertTextAfter(lastValueToken, ")")
+                                    );
+                                }
+                            }
+
+                            /*
+                             * If the last token of the return statement is semicolon, remove it.
+                             * Non-block arrow body is an expression, not a statement.
+                             */
+                            if (astUtils.isSemicolonToken(lastValueToken)) {
+                                fixes.push(fixer.remove(lastValueToken));
+                            }
+
+                            return fixes;
+                        }
+                    });
+                }
+            } else {
+                if (always || (asNeeded && requireReturnForObjectLiteral && arrowBody.type === "ObjectExpression")) {
+                    context.report({
+                        node,
+                        loc: arrowBody.loc,
+                        messageId: "expectedBlock",
+                        fix(fixer) {
+                            const fixes = [];
+                            const arrowToken = sourceCode.getTokenBefore(arrowBody, astUtils.isArrowToken);
+                            const [firstTokenAfterArrow, secondTokenAfterArrow] = sourceCode.getTokensAfter(arrowToken, { count: 2 });
+                            const lastToken = sourceCode.getLastToken(node);
+
+                            let parenthesisedObjectLiteral = null;
+
+                            if (
+                                astUtils.isOpeningParenToken(firstTokenAfterArrow) &&
+                                astUtils.isOpeningBraceToken(secondTokenAfterArrow)
+                            ) {
+                                const braceNode = sourceCode.getNodeByRangeIndex(secondTokenAfterArrow.range[0]);
+
+                                if (braceNode.type === "ObjectExpression") {
+                                    parenthesisedObjectLiteral = braceNode;
+                                }
+                            }
+
+                            // If the value is object literal, remove parentheses which were forced by syntax.
+                            if (parenthesisedObjectLiteral) {
+                                const openingParenToken = firstTokenAfterArrow;
+                                const openingBraceToken = secondTokenAfterArrow;
+
+                                if (astUtils.isTokenOnSameLine(openingParenToken, openingBraceToken)) {
+                                    fixes.push(fixer.replaceText(openingParenToken, "{return "));
+                                } else {
+
+                                    // Avoid ASI
+                                    fixes.push(
+                                        fixer.replaceText(openingParenToken, "{"),
+                                        fixer.insertTextBefore(openingBraceToken, "return ")
+                                    );
+                                }
+
+                                // Closing paren for the object doesn't have to be lastToken, e.g.: () => ({}).foo()
+                                fixes.push(fixer.remove(findClosingParen(parenthesisedObjectLiteral)));
+                                fixes.push(fixer.insertTextAfter(lastToken, "}"));
+
+                            } else {
+                                fixes.push(fixer.insertTextBefore(firstTokenAfterArrow, "{return "));
+                                fixes.push(fixer.insertTextAfter(lastToken, "}"));
+                            }
+
+                            return fixes;
+                        }
+                    });
+                }
+            }
+        }
+
+        return {
+            "BinaryExpression[operator='in']"() {
+                let info = funcInfo;
+
+                while (info) {
+                    info.hasInOperator = true;
+                    info = info.upper;
+                }
+            },
+            ArrowFunctionExpression() {
+                funcInfo = {
+                    upper: funcInfo,
+                    hasInOperator: false
+                };
+            },
+            "ArrowFunctionExpression:exit"(node) {
+                validate(node);
+                funcInfo = funcInfo.upper;
+            }
+        };
+    }
+};