/** * @fileoverview Disallow parenthesising higher precedence subexpressions. * @author Michael Ficarra * @deprecated in ESLint v8.53.0 */ "use strict"; //------------------------------------------------------------------------------ // Rule Definition //------------------------------------------------------------------------------ const { isParenthesized: isParenthesizedRaw, } = require("@eslint-community/eslint-utils"); const astUtils = require("./utils/ast-utils.js"); /** @type {import('../types').Rule.RuleModule} */ module.exports = { meta: { deprecated: { message: "Formatting rules are being moved out of ESLint core.", url: "https://eslint.org/blog/2023/10/deprecating-formatting-rules/", deprecatedSince: "8.53.0", availableUntil: "10.0.0", replacedBy: [ { message: "ESLint Stylistic now maintains deprecated stylistic core rules.", url: "https://eslint.style/guide/migration", plugin: { name: "@stylistic/eslint-plugin-js", url: "https://eslint.style/packages/js", }, rule: { name: "no-extra-parens", url: "https://eslint.style/rules/js/no-extra-parens", }, }, ], }, type: "layout", docs: { description: "Disallow unnecessary parentheses", recommended: false, url: "https://eslint.org/docs/latest/rules/no-extra-parens", }, fixable: "code", schema: { anyOf: [ { type: "array", items: [ { enum: ["functions"], }, ], minItems: 0, maxItems: 1, }, { type: "array", items: [ { enum: ["all"], }, { type: "object", properties: { conditionalAssign: { type: "boolean" }, ternaryOperandBinaryExpressions: { type: "boolean", }, nestedBinaryExpressions: { type: "boolean" }, returnAssign: { type: "boolean" }, ignoreJSX: { enum: [ "none", "all", "single-line", "multi-line", ], }, enforceForArrowConditionals: { type: "boolean", }, enforceForSequenceExpressions: { type: "boolean", }, enforceForNewInMemberExpressions: { type: "boolean", }, enforceForFunctionPrototypeMethods: { type: "boolean", }, allowParensAfterCommentPattern: { type: "string", }, }, additionalProperties: false, }, ], minItems: 0, maxItems: 2, }, ], }, messages: { unexpected: "Unnecessary parentheses around expression.", }, }, create(context) { const sourceCode = context.sourceCode; const tokensToIgnore = new WeakSet(); const precedence = astUtils.getPrecedence; const ALL_NODES = context.options[0] !== "functions"; const EXCEPT_COND_ASSIGN = ALL_NODES && context.options[1] && context.options[1].conditionalAssign === false; const EXCEPT_COND_TERNARY = ALL_NODES && context.options[1] && context.options[1].ternaryOperandBinaryExpressions === false; const NESTED_BINARY = ALL_NODES && context.options[1] && context.options[1].nestedBinaryExpressions === false; const EXCEPT_RETURN_ASSIGN = ALL_NODES && context.options[1] && context.options[1].returnAssign === false; const IGNORE_JSX = ALL_NODES && context.options[1] && context.options[1].ignoreJSX; const IGNORE_ARROW_CONDITIONALS = ALL_NODES && context.options[1] && context.options[1].enforceForArrowConditionals === false; const IGNORE_SEQUENCE_EXPRESSIONS = ALL_NODES && context.options[1] && context.options[1].enforceForSequenceExpressions === false; const IGNORE_NEW_IN_MEMBER_EXPR = ALL_NODES && context.options[1] && context.options[1].enforceForNewInMemberExpressions === false; const IGNORE_FUNCTION_PROTOTYPE_METHODS = ALL_NODES && context.options[1] && context.options[1].enforceForFunctionPrototypeMethods === false; const ALLOW_PARENS_AFTER_COMMENT_PATTERN = ALL_NODES && context.options[1] && context.options[1].allowParensAfterCommentPattern; const PRECEDENCE_OF_ASSIGNMENT_EXPR = precedence({ type: "AssignmentExpression", }); const PRECEDENCE_OF_UPDATE_EXPR = precedence({ type: "UpdateExpression", }); let reportsBuffer; /** * Determines whether the given node is a `call` or `apply` method call, invoked directly on a `FunctionExpression` node. * Example: function(){}.call() * @param {ASTNode} node The node to be checked. * @returns {boolean} True if the node is an immediate `call` or `apply` method call. * @private */ function isImmediateFunctionPrototypeMethodCall(node) { const callNode = astUtils.skipChainExpression(node); if (callNode.type !== "CallExpression") { return false; } const callee = astUtils.skipChainExpression(callNode.callee); return ( callee.type === "MemberExpression" && callee.object.type === "FunctionExpression" && ["call", "apply"].includes( astUtils.getStaticPropertyName(callee), ) ); } /** * Determines if this rule should be enforced for a node given the current configuration. * @param {ASTNode} node The node to be checked. * @returns {boolean} True if the rule should be enforced for this node. * @private */ function ruleApplies(node) { if (node.type === "JSXElement" || node.type === "JSXFragment") { const isSingleLine = node.loc.start.line === node.loc.end.line; switch (IGNORE_JSX) { // Exclude this JSX element from linting case "all": return false; // Exclude this JSX element if it is multi-line element case "multi-line": return isSingleLine; // Exclude this JSX element if it is single-line element case "single-line": return !isSingleLine; // Nothing special to be done for JSX elements case "none": break; // no default } } if ( node.type === "SequenceExpression" && IGNORE_SEQUENCE_EXPRESSIONS ) { return false; } if ( isImmediateFunctionPrototypeMethodCall(node) && IGNORE_FUNCTION_PROTOTYPE_METHODS ) { return false; } return ( ALL_NODES || node.type === "FunctionExpression" || node.type === "ArrowFunctionExpression" ); } /** * Determines if a node is surrounded by parentheses. * @param {ASTNode} node The node to be checked. * @returns {boolean} True if the node is parenthesised. * @private */ function isParenthesised(node) { return isParenthesizedRaw(1, node, sourceCode); } /** * Determines if a node is surrounded by parentheses twice. * @param {ASTNode} node The node to be checked. * @returns {boolean} True if the node is doubly parenthesised. * @private */ function isParenthesisedTwice(node) { return isParenthesizedRaw(2, node, sourceCode); } /** * Determines if a node is surrounded by (potentially) invalid parentheses. * @param {ASTNode} node The node to be checked. * @returns {boolean} True if the node is incorrectly parenthesised. * @private */ function hasExcessParens(node) { return ruleApplies(node) && isParenthesised(node); } /** * Determines if a node that is expected to be parenthesised is surrounded by * (potentially) invalid extra parentheses. * @param {ASTNode} node The node to be checked. * @returns {boolean} True if the node is has an unexpected extra pair of parentheses. * @private */ function hasDoubleExcessParens(node) { return ruleApplies(node) && isParenthesisedTwice(node); } /** * Determines if a node that is expected to be parenthesised is surrounded by * (potentially) invalid extra parentheses with considering precedence level of the node. * If the preference level of the node is not higher or equal to precedence lower limit, it also checks * whether the node is surrounded by parentheses twice or not. * @param {ASTNode} node The node to be checked. * @param {number} precedenceLowerLimit The lower limit of precedence. * @returns {boolean} True if the node is has an unexpected extra pair of parentheses. * @private */ function hasExcessParensWithPrecedence(node, precedenceLowerLimit) { if (ruleApplies(node) && isParenthesised(node)) { if ( precedence(node) >= precedenceLowerLimit || isParenthesisedTwice(node) ) { return true; } } return false; } /** * Determines if a node test expression is allowed to have a parenthesised assignment * @param {ASTNode} node The node to be checked. * @returns {boolean} True if the assignment can be parenthesised. * @private */ function isCondAssignException(node) { return ( EXCEPT_COND_ASSIGN && node.test.type === "AssignmentExpression" ); } /** * Determines if a node is in a return statement * @param {ASTNode} node The node to be checked. * @returns {boolean} True if the node is in a return statement. * @private */ function isInReturnStatement(node) { for ( let currentNode = node; currentNode; currentNode = currentNode.parent ) { if ( currentNode.type === "ReturnStatement" || (currentNode.type === "ArrowFunctionExpression" && currentNode.body.type !== "BlockStatement") ) { return true; } } return false; } /** * Determines if a constructor function is newed-up with parens * @param {ASTNode} newExpression The NewExpression node to be checked. * @returns {boolean} True if the constructor is called with parens. * @private */ function isNewExpressionWithParens(newExpression) { const lastToken = sourceCode.getLastToken(newExpression); const penultimateToken = sourceCode.getTokenBefore(lastToken); return ( newExpression.arguments.length > 0 || // The expression should end with its own parens, e.g., new new foo() is not a new expression with parens (astUtils.isOpeningParenToken(penultimateToken) && astUtils.isClosingParenToken(lastToken) && newExpression.callee.range[1] < newExpression.range[1]) ); } /** * Determines if a node is or contains an assignment expression * @param {ASTNode} node The node to be checked. * @returns {boolean} True if the node is or contains an assignment expression. * @private */ function containsAssignment(node) { if (node.type === "AssignmentExpression") { return true; } if ( node.type === "ConditionalExpression" && (node.consequent.type === "AssignmentExpression" || node.alternate.type === "AssignmentExpression") ) { return true; } if ( (node.left && node.left.type === "AssignmentExpression") || (node.right && node.right.type === "AssignmentExpression") ) { return true; } return false; } /** * Determines if a node is contained by or is itself a return statement and is allowed to have a parenthesised assignment * @param {ASTNode} node The node to be checked. * @returns {boolean} True if the assignment can be parenthesised. * @private */ function isReturnAssignException(node) { if (!EXCEPT_RETURN_ASSIGN || !isInReturnStatement(node)) { return false; } if (node.type === "ReturnStatement") { return node.argument && containsAssignment(node.argument); } if ( node.type === "ArrowFunctionExpression" && node.body.type !== "BlockStatement" ) { return containsAssignment(node.body); } return containsAssignment(node); } /** * Determines if a node following a [no LineTerminator here] restriction is * surrounded by (potentially) invalid extra parentheses. * @param {Token} token The token preceding the [no LineTerminator here] restriction. * @param {ASTNode} node The node to be checked. * @returns {boolean} True if the node is incorrectly parenthesised. * @private */ function hasExcessParensNoLineTerminator(token, node) { if (token.loc.end.line === node.loc.start.line) { return hasExcessParens(node); } return hasDoubleExcessParens(node); } /** * Determines whether a node should be preceded by an additional space when removing parens * @param {ASTNode} node node to evaluate; must be surrounded by parentheses * @returns {boolean} `true` if a space should be inserted before the node * @private */ function requiresLeadingSpace(node) { const leftParenToken = sourceCode.getTokenBefore(node); const tokenBeforeLeftParen = sourceCode.getTokenBefore( leftParenToken, { includeComments: true }, ); const tokenAfterLeftParen = sourceCode.getTokenAfter( leftParenToken, { includeComments: true }, ); return ( tokenBeforeLeftParen && tokenBeforeLeftParen.range[1] === leftParenToken.range[0] && leftParenToken.range[1] === tokenAfterLeftParen.range[0] && !astUtils.canTokensBeAdjacent( tokenBeforeLeftParen, tokenAfterLeftParen, ) ); } /** * Determines whether a node should be followed by an additional space when removing parens * @param {ASTNode} node node to evaluate; must be surrounded by parentheses * @returns {boolean} `true` if a space should be inserted after the node * @private */ function requiresTrailingSpace(node) { const nextTwoTokens = sourceCode.getTokensAfter(node, { count: 2 }); const rightParenToken = nextTwoTokens[0]; const tokenAfterRightParen = nextTwoTokens[1]; const tokenBeforeRightParen = sourceCode.getLastToken(node); return ( rightParenToken && tokenAfterRightParen && !sourceCode.isSpaceBetweenTokens( rightParenToken, tokenAfterRightParen, ) && !astUtils.canTokensBeAdjacent( tokenBeforeRightParen, tokenAfterRightParen, ) ); } /** * Determines if a given expression node is an IIFE * @param {ASTNode} node The node to check * @returns {boolean} `true` if the given node is an IIFE */ function isIIFE(node) { const maybeCallNode = astUtils.skipChainExpression(node); return ( maybeCallNode.type === "CallExpression" && maybeCallNode.callee.type === "FunctionExpression" ); } /** * Determines if the given node can be the assignment target in destructuring or the LHS of an assignment. * This is to avoid an autofix that could change behavior because parsers mistakenly allow invalid syntax, * such as `(a = b) = c` and `[(a = b) = c] = []`. Ideally, this function shouldn't be necessary. * @param {ASTNode} [node] The node to check * @returns {boolean} `true` if the given node can be a valid assignment target */ function canBeAssignmentTarget(node) { return ( node && (node.type === "Identifier" || node.type === "MemberExpression") ); } /** * Checks if a node is fixable. * A node is fixable if removing a single pair of surrounding parentheses does not turn it * into a directive after fixing other nodes. * Almost all nodes are fixable, except if all of the following conditions are met: * The node is a string Literal * It has a single pair of parentheses * It is the only child of an ExpressionStatement * @param {ASTNode} node The node to evaluate. * @returns {boolean} Whether or not the node is fixable. * @private */ function isFixable(node) { // if it's not a string literal it can be autofixed if (node.type !== "Literal" || typeof node.value !== "string") { return true; } if (isParenthesisedTwice(node)) { return true; } return !astUtils.isTopLevelExpressionStatement(node.parent); } /** * Report the node * @param {ASTNode} node node to evaluate * @returns {void} * @private */ function report(node) { const leftParenToken = sourceCode.getTokenBefore(node); const rightParenToken = sourceCode.getTokenAfter(node); if (!isParenthesisedTwice(node)) { if (tokensToIgnore.has(sourceCode.getFirstToken(node))) { return; } if (isIIFE(node) && !isParenthesised(node.callee)) { return; } if (ALLOW_PARENS_AFTER_COMMENT_PATTERN) { const commentsBeforeLeftParenToken = sourceCode.getCommentsBefore(leftParenToken); const totalCommentsBeforeLeftParenTokenCount = commentsBeforeLeftParenToken.length; const ignorePattern = new RegExp( ALLOW_PARENS_AFTER_COMMENT_PATTERN, "u", ); if ( totalCommentsBeforeLeftParenTokenCount > 0 && ignorePattern.test( commentsBeforeLeftParenToken[ totalCommentsBeforeLeftParenTokenCount - 1 ].value, ) ) { return; } } } /** * Finishes reporting * @returns {void} * @private */ function finishReport() { context.report({ node, loc: leftParenToken.loc, messageId: "unexpected", fix: isFixable(node) ? fixer => { const parenthesizedSource = sourceCode.text.slice( leftParenToken.range[1], rightParenToken.range[0], ); return fixer.replaceTextRange( [ leftParenToken.range[0], rightParenToken.range[1], ], (requiresLeadingSpace(node) ? " " : "") + parenthesizedSource + (requiresTrailingSpace(node) ? " " : ""), ); } : null, }); } if (reportsBuffer) { reportsBuffer.reports.push({ node, finishReport }); return; } finishReport(); } /** * Evaluate a argument of the node. * @param {ASTNode} node node to evaluate * @returns {void} * @private */ function checkArgumentWithPrecedence(node) { if ( hasExcessParensWithPrecedence(node.argument, precedence(node)) ) { report(node.argument); } } /** * Check if a member expression contains a call expression * @param {ASTNode} node MemberExpression node to evaluate * @returns {boolean} true if found, false if not */ function doesMemberExpressionContainCallExpression(node) { let currentNode = node.object; let currentNodeType = node.object.type; while (currentNodeType === "MemberExpression") { currentNode = currentNode.object; currentNodeType = currentNode.type; } return currentNodeType === "CallExpression"; } /** * Evaluate a new call * @param {ASTNode} node node to evaluate * @returns {void} * @private */ function checkCallNew(node) { const callee = node.callee; if (hasExcessParensWithPrecedence(callee, precedence(node))) { if ( hasDoubleExcessParens(callee) || !( isIIFE(node) || // (new A)(); new (new A)(); (callee.type === "NewExpression" && !isNewExpressionWithParens(callee) && !( node.type === "NewExpression" && !isNewExpressionWithParens(node) )) || // new (a().b)(); new (a.b().c); (node.type === "NewExpression" && callee.type === "MemberExpression" && doesMemberExpressionContainCallExpression( callee, )) || // (a?.b)(); (a?.())(); (!node.optional && callee.type === "ChainExpression") ) ) { report(node.callee); } } node.arguments .filter(arg => hasExcessParensWithPrecedence( arg, PRECEDENCE_OF_ASSIGNMENT_EXPR, ), ) .forEach(report); } /** * Evaluate binary logicals * @param {ASTNode} node node to evaluate * @returns {void} * @private */ function checkBinaryLogical(node) { const prec = precedence(node); const leftPrecedence = precedence(node.left); const rightPrecedence = precedence(node.right); const isExponentiation = node.operator === "**"; const shouldSkipLeft = NESTED_BINARY && (node.left.type === "BinaryExpression" || node.left.type === "LogicalExpression"); const shouldSkipRight = NESTED_BINARY && (node.right.type === "BinaryExpression" || node.right.type === "LogicalExpression"); if (!shouldSkipLeft && hasExcessParens(node.left)) { if ( (!( ["AwaitExpression", "UnaryExpression"].includes( node.left.type, ) && isExponentiation ) && !astUtils.isMixedLogicalAndCoalesceExpressions( node.left, node, ) && (leftPrecedence > prec || (leftPrecedence === prec && !isExponentiation))) || isParenthesisedTwice(node.left) ) { report(node.left); } } if (!shouldSkipRight && hasExcessParens(node.right)) { if ( (!astUtils.isMixedLogicalAndCoalesceExpressions( node.right, node, ) && (rightPrecedence > prec || (rightPrecedence === prec && isExponentiation))) || isParenthesisedTwice(node.right) ) { report(node.right); } } } /** * Check the parentheses around the super class of the given class definition. * @param {ASTNode} node The node of class declarations to check. * @returns {void} */ function checkClass(node) { if (!node.superClass) { return; } /* * If `node.superClass` is a LeftHandSideExpression, parentheses are extra. * Otherwise, parentheses are needed. */ const hasExtraParens = precedence(node.superClass) > PRECEDENCE_OF_UPDATE_EXPR ? hasExcessParens(node.superClass) : hasDoubleExcessParens(node.superClass); if (hasExtraParens) { report(node.superClass); } } /** * Check the parentheses around the argument of the given spread operator. * @param {ASTNode} node The node of spread elements/properties to check. * @returns {void} */ function checkSpreadOperator(node) { if ( hasExcessParensWithPrecedence( node.argument, PRECEDENCE_OF_ASSIGNMENT_EXPR, ) ) { report(node.argument); } } /** * Checks the parentheses for an ExpressionStatement or ExportDefaultDeclaration * @param {ASTNode} node The ExpressionStatement.expression or ExportDefaultDeclaration.declaration node * @returns {void} */ function checkExpressionOrExportStatement(node) { const firstToken = isParenthesised(node) ? sourceCode.getTokenBefore(node) : sourceCode.getFirstToken(node); const secondToken = sourceCode.getTokenAfter( firstToken, astUtils.isNotOpeningParenToken, ); const thirdToken = secondToken ? sourceCode.getTokenAfter(secondToken) : null; const tokenAfterClosingParens = secondToken ? sourceCode.getTokenAfter( secondToken, astUtils.isNotClosingParenToken, ) : null; if ( astUtils.isOpeningParenToken(firstToken) && (astUtils.isOpeningBraceToken(secondToken) || (secondToken.type === "Keyword" && (secondToken.value === "function" || secondToken.value === "class" || (secondToken.value === "let" && tokenAfterClosingParens && (astUtils.isOpeningBracketToken( tokenAfterClosingParens, ) || tokenAfterClosingParens.type === "Identifier")))) || (secondToken && secondToken.type === "Identifier" && secondToken.value === "async" && thirdToken && thirdToken.type === "Keyword" && thirdToken.value === "function")) ) { tokensToIgnore.add(secondToken); } const hasExtraParens = node.parent.type === "ExportDefaultDeclaration" ? hasExcessParensWithPrecedence( node, PRECEDENCE_OF_ASSIGNMENT_EXPR, ) : hasExcessParens(node); if (hasExtraParens) { report(node); } } /** * Finds the path from the given node to the specified ancestor. * @param {ASTNode} node First node in the path. * @param {ASTNode} ancestor Last node in the path. * @returns {ASTNode[]} Path, including both nodes. * @throws {Error} If the given node does not have the specified ancestor. */ function pathToAncestor(node, ancestor) { const path = [node]; let currentNode = node; while (currentNode !== ancestor) { currentNode = currentNode.parent; /* c8 ignore start */ if (currentNode === null) { throw new Error( "Nodes are not in the ancestor-descendant relationship.", ); } /* c8 ignore stop */ path.push(currentNode); } return path; } /** * Finds the path from the given node to the specified descendant. * @param {ASTNode} node First node in the path. * @param {ASTNode} descendant Last node in the path. * @returns {ASTNode[]} Path, including both nodes. * @throws {Error} If the given node does not have the specified descendant. */ function pathToDescendant(node, descendant) { return pathToAncestor(descendant, node).reverse(); } /** * Checks whether the syntax of the given ancestor of an 'in' expression inside a for-loop initializer * is preventing the 'in' keyword from being interpreted as a part of an ill-formed for-in loop. * @param {ASTNode} node Ancestor of an 'in' expression. * @param {ASTNode} child Child of the node, ancestor of the same 'in' expression or the 'in' expression itself. * @returns {boolean} True if the keyword 'in' would be interpreted as the 'in' operator, without any parenthesis. */ function isSafelyEnclosingInExpression(node, child) { switch (node.type) { case "ArrayExpression": case "ArrayPattern": case "BlockStatement": case "ObjectExpression": case "ObjectPattern": case "TemplateLiteral": return true; case "ArrowFunctionExpression": case "FunctionExpression": return node.params.includes(child); case "CallExpression": case "NewExpression": return node.arguments.includes(child); case "MemberExpression": return node.computed && node.property === child; case "ConditionalExpression": return node.consequent === child; default: return false; } } /** * Starts a new reports buffering. Warnings will be stored in a buffer instead of being reported immediately. * An additional logic that requires multiple nodes (e.g. a whole subtree) may dismiss some of the stored warnings. * @returns {void} */ function startNewReportsBuffering() { reportsBuffer = { upper: reportsBuffer, inExpressionNodes: [], reports: [], }; } /** * Ends the current reports buffering. * @returns {void} */ function endCurrentReportsBuffering() { const { upper, inExpressionNodes, reports } = reportsBuffer; if (upper) { upper.inExpressionNodes.push(...inExpressionNodes); upper.reports.push(...reports); } else { // flush remaining reports reports.forEach(({ finishReport }) => finishReport()); } reportsBuffer = upper; } /** * Checks whether the given node is in the current reports buffer. * @param {ASTNode} node Node to check. * @returns {boolean} True if the node is in the current buffer, false otherwise. */ function isInCurrentReportsBuffer(node) { return reportsBuffer.reports.some(r => r.node === node); } /** * Removes the given node from the current reports buffer. * @param {ASTNode} node Node to remove. * @returns {void} */ function removeFromCurrentReportsBuffer(node) { reportsBuffer.reports = reportsBuffer.reports.filter( r => r.node !== node, ); } /** * Checks whether a node is a MemberExpression at NewExpression's callee. * @param {ASTNode} node node to check. * @returns {boolean} True if the node is a MemberExpression at NewExpression's callee. false otherwise. */ function isMemberExpInNewCallee(node) { if (node.type === "MemberExpression") { return node.parent.type === "NewExpression" && node.parent.callee === node ? true : node.parent.object === node && isMemberExpInNewCallee(node.parent); } return false; } /** * Checks if the left-hand side of an assignment is an identifier, the operator is one of * `=`, `&&=`, `||=` or `??=` and the right-hand side is an anonymous class or function. * * As per https://tc39.es/ecma262/#sec-assignment-operators-runtime-semantics-evaluation, an * assignment involving one of the operators `=`, `&&=`, `||=` or `??=` where the right-hand * side is an anonymous class or function and the left-hand side is an *unparenthesized* * identifier has different semantics than other assignments. * Specifically, when an expression like `foo = function () {}` is evaluated, `foo.name` * will be set to the string "foo", i.e. the identifier name. The same thing does not happen * when evaluating `(foo) = function () {}`. * Since the parenthesizing of the identifier in the left-hand side is significant in this * special case, the parentheses, if present, should not be flagged as unnecessary. * @param {ASTNode} node an AssignmentExpression node. * @returns {boolean} `true` if the left-hand side of the assignment is an identifier, the * operator is one of `=`, `&&=`, `||=` or `??=` and the right-hand side is an anonymous * class or function; otherwise, `false`. */ function isAnonymousFunctionAssignmentException({ left, operator, right, }) { if ( left.type === "Identifier" && ["=", "&&=", "||=", "??="].includes(operator) ) { const rhsType = right.type; if (rhsType === "ArrowFunctionExpression") { return true; } if ( (rhsType === "FunctionExpression" || rhsType === "ClassExpression") && !right.id ) { return true; } } return false; } return { ArrayExpression(node) { node.elements .filter( e => e && hasExcessParensWithPrecedence( e, PRECEDENCE_OF_ASSIGNMENT_EXPR, ), ) .forEach(report); }, ArrayPattern(node) { node.elements .filter(e => canBeAssignmentTarget(e) && hasExcessParens(e)) .forEach(report); }, ArrowFunctionExpression(node) { if (isReturnAssignException(node)) { return; } if ( node.body.type === "ConditionalExpression" && IGNORE_ARROW_CONDITIONALS ) { return; } if (node.body.type !== "BlockStatement") { const firstBodyToken = sourceCode.getFirstToken( node.body, astUtils.isNotOpeningParenToken, ); const tokenBeforeFirst = sourceCode.getTokenBefore(firstBodyToken); if ( astUtils.isOpeningParenToken(tokenBeforeFirst) && astUtils.isOpeningBraceToken(firstBodyToken) ) { tokensToIgnore.add(firstBodyToken); } if ( hasExcessParensWithPrecedence( node.body, PRECEDENCE_OF_ASSIGNMENT_EXPR, ) ) { report(node.body); } } }, AssignmentExpression(node) { if ( canBeAssignmentTarget(node.left) && hasExcessParens(node.left) && (!isAnonymousFunctionAssignmentException(node) || isParenthesisedTwice(node.left)) ) { report(node.left); } if ( !isReturnAssignException(node) && hasExcessParensWithPrecedence(node.right, precedence(node)) ) { report(node.right); } }, BinaryExpression(node) { if (reportsBuffer && node.operator === "in") { reportsBuffer.inExpressionNodes.push(node); } checkBinaryLogical(node); }, CallExpression: checkCallNew, ConditionalExpression(node) { if (isReturnAssignException(node)) { return; } const availableTypes = new Set([ "BinaryExpression", "LogicalExpression", ]); if ( !( EXCEPT_COND_TERNARY && availableTypes.has(node.test.type) ) && !isCondAssignException(node) && hasExcessParensWithPrecedence( node.test, precedence({ type: "LogicalExpression", operator: "||", }), ) ) { report(node.test); } if ( !( EXCEPT_COND_TERNARY && availableTypes.has(node.consequent.type) ) && hasExcessParensWithPrecedence( node.consequent, PRECEDENCE_OF_ASSIGNMENT_EXPR, ) ) { report(node.consequent); } if ( !( EXCEPT_COND_TERNARY && availableTypes.has(node.alternate.type) ) && hasExcessParensWithPrecedence( node.alternate, PRECEDENCE_OF_ASSIGNMENT_EXPR, ) ) { report(node.alternate); } }, DoWhileStatement(node) { if ( hasExcessParens(node.test) && !isCondAssignException(node) ) { report(node.test); } }, ExportDefaultDeclaration: node => checkExpressionOrExportStatement(node.declaration), ExpressionStatement: node => checkExpressionOrExportStatement(node.expression), ForInStatement(node) { if (node.left.type !== "VariableDeclaration") { const firstLeftToken = sourceCode.getFirstToken( node.left, astUtils.isNotOpeningParenToken, ); if ( firstLeftToken.value === "let" && astUtils.isOpeningBracketToken( sourceCode.getTokenAfter( firstLeftToken, astUtils.isNotClosingParenToken, ), ) ) { // ForInStatement#left expression cannot start with `let[`. tokensToIgnore.add(firstLeftToken); } } if (hasExcessParens(node.left)) { report(node.left); } if (hasExcessParens(node.right)) { report(node.right); } }, ForOfStatement(node) { if (node.left.type !== "VariableDeclaration") { const firstLeftToken = sourceCode.getFirstToken( node.left, astUtils.isNotOpeningParenToken, ); if (firstLeftToken.value === "let") { // ForOfStatement#left expression cannot start with `let`. tokensToIgnore.add(firstLeftToken); } } if (hasExcessParens(node.left)) { report(node.left); } if ( hasExcessParensWithPrecedence( node.right, PRECEDENCE_OF_ASSIGNMENT_EXPR, ) ) { report(node.right); } }, ForStatement(node) { if ( node.test && hasExcessParens(node.test) && !isCondAssignException(node) ) { report(node.test); } if (node.update && hasExcessParens(node.update)) { report(node.update); } if (node.init) { if (node.init.type !== "VariableDeclaration") { const firstToken = sourceCode.getFirstToken( node.init, astUtils.isNotOpeningParenToken, ); if ( firstToken.value === "let" && astUtils.isOpeningBracketToken( sourceCode.getTokenAfter( firstToken, astUtils.isNotClosingParenToken, ), ) ) { // ForStatement#init expression cannot start with `let[`. tokensToIgnore.add(firstToken); } } startNewReportsBuffering(); if (hasExcessParens(node.init)) { report(node.init); } } }, "ForStatement > *.init:exit"(node) { /* * Removing parentheses around `in` expressions might change semantics and cause errors. * * For example, this valid for loop: * for (let a = (b in c); ;); * after removing parentheses would be treated as an invalid for-in loop: * for (let a = b in c; ;); */ if (reportsBuffer.reports.length) { reportsBuffer.inExpressionNodes.forEach( inExpressionNode => { const path = pathToDescendant( node, inExpressionNode, ); let nodeToExclude; for (let i = 0; i < path.length; i++) { const pathNode = path[i]; if (i < path.length - 1) { const nextPathNode = path[i + 1]; if ( isSafelyEnclosingInExpression( pathNode, nextPathNode, ) ) { // The 'in' expression in safely enclosed by the syntax of its ancestor nodes (e.g. by '{}' or '[]'). return; } } if (isParenthesised(pathNode)) { if (isInCurrentReportsBuffer(pathNode)) { // This node was supposed to be reported, but parentheses might be necessary. if (isParenthesisedTwice(pathNode)) { /* * This node is parenthesised twice, it certainly has at least one pair of `extra` parentheses. * If the --fix option is on, the current fixing iteration will remove only one pair of parentheses. * The remaining pair is safely enclosing the 'in' expression. */ return; } // Exclude the outermost node only. if (!nodeToExclude) { nodeToExclude = pathNode; } // Don't break the loop here, there might be some safe nodes or parentheses that will stay inside. } else { // This node will stay parenthesised, the 'in' expression in safely enclosed by '()'. return; } } } // Exclude the node from the list (i.e. treat parentheses as necessary) removeFromCurrentReportsBuffer(nodeToExclude); }, ); } endCurrentReportsBuffering(); }, IfStatement(node) { if ( hasExcessParens(node.test) && !isCondAssignException(node) ) { report(node.test); } }, ImportExpression(node) { const { source } = node; if (source.type === "SequenceExpression") { if (hasDoubleExcessParens(source)) { report(source); } } else if (hasExcessParens(source)) { report(source); } }, LogicalExpression: checkBinaryLogical, MemberExpression(node) { const shouldAllowWrapOnce = isMemberExpInNewCallee(node) && doesMemberExpressionContainCallExpression(node); const nodeObjHasExcessParens = shouldAllowWrapOnce ? hasDoubleExcessParens(node.object) : hasExcessParens(node.object) && !( isImmediateFunctionPrototypeMethodCall( node.parent, ) && node.parent.callee === node && IGNORE_FUNCTION_PROTOTYPE_METHODS ); if ( nodeObjHasExcessParens && precedence(node.object) >= precedence(node) && (node.computed || !( astUtils.isDecimalInteger(node.object) || // RegExp literal is allowed to have parens (#1589) (node.object.type === "Literal" && node.object.regex) )) ) { report(node.object); } if ( nodeObjHasExcessParens && node.object.type === "CallExpression" ) { report(node.object); } if ( nodeObjHasExcessParens && !IGNORE_NEW_IN_MEMBER_EXPR && node.object.type === "NewExpression" && isNewExpressionWithParens(node.object) ) { report(node.object); } if ( nodeObjHasExcessParens && node.optional && node.object.type === "ChainExpression" ) { report(node.object); } if (node.computed && hasExcessParens(node.property)) { report(node.property); } }, "MethodDefinition[computed=true]"(node) { if ( hasExcessParensWithPrecedence( node.key, PRECEDENCE_OF_ASSIGNMENT_EXPR, ) ) { report(node.key); } }, NewExpression: checkCallNew, ObjectExpression(node) { node.properties .filter( property => property.value && hasExcessParensWithPrecedence( property.value, PRECEDENCE_OF_ASSIGNMENT_EXPR, ), ) .forEach(property => report(property.value)); }, ObjectPattern(node) { node.properties .filter(property => { const value = property.value; return ( canBeAssignmentTarget(value) && hasExcessParens(value) ); }) .forEach(property => report(property.value)); }, Property(node) { if (node.computed) { const { key } = node; if ( key && hasExcessParensWithPrecedence( key, PRECEDENCE_OF_ASSIGNMENT_EXPR, ) ) { report(key); } } }, PropertyDefinition(node) { if ( node.computed && hasExcessParensWithPrecedence( node.key, PRECEDENCE_OF_ASSIGNMENT_EXPR, ) ) { report(node.key); } if ( node.value && hasExcessParensWithPrecedence( node.value, PRECEDENCE_OF_ASSIGNMENT_EXPR, ) ) { report(node.value); } }, RestElement(node) { const argument = node.argument; if ( canBeAssignmentTarget(argument) && hasExcessParens(argument) ) { report(argument); } }, ReturnStatement(node) { const returnToken = sourceCode.getFirstToken(node); if (isReturnAssignException(node)) { return; } if ( node.argument && hasExcessParensNoLineTerminator( returnToken, node.argument, ) && // RegExp literal is allowed to have parens (#1589) !(node.argument.type === "Literal" && node.argument.regex) ) { report(node.argument); } }, SequenceExpression(node) { const precedenceOfNode = precedence(node); node.expressions .filter(e => hasExcessParensWithPrecedence(e, precedenceOfNode), ) .forEach(report); }, SwitchCase(node) { if (node.test && hasExcessParens(node.test)) { report(node.test); } }, SwitchStatement(node) { if (hasExcessParens(node.discriminant)) { report(node.discriminant); } }, ThrowStatement(node) { const throwToken = sourceCode.getFirstToken(node); if ( hasExcessParensNoLineTerminator(throwToken, node.argument) ) { report(node.argument); } }, UnaryExpression: checkArgumentWithPrecedence, UpdateExpression(node) { if (node.prefix) { checkArgumentWithPrecedence(node); } else { const { argument } = node; const operatorToken = sourceCode.getLastToken(node); if ( argument.loc.end.line === operatorToken.loc.start.line ) { checkArgumentWithPrecedence(node); } else { if (hasDoubleExcessParens(argument)) { report(argument); } } } }, AwaitExpression: checkArgumentWithPrecedence, VariableDeclarator(node) { if ( node.init && hasExcessParensWithPrecedence( node.init, PRECEDENCE_OF_ASSIGNMENT_EXPR, ) && // RegExp literal is allowed to have parens (#1589) !(node.init.type === "Literal" && node.init.regex) ) { report(node.init); } }, WhileStatement(node) { if ( hasExcessParens(node.test) && !isCondAssignException(node) ) { report(node.test); } }, WithStatement(node) { if (hasExcessParens(node.object)) { report(node.object); } }, YieldExpression(node) { if (node.argument) { const yieldToken = sourceCode.getFirstToken(node); if ( (precedence(node.argument) >= precedence(node) && hasExcessParensNoLineTerminator( yieldToken, node.argument, )) || hasDoubleExcessParens(node.argument) ) { report(node.argument); } } }, ClassDeclaration: checkClass, ClassExpression: checkClass, SpreadElement: checkSpreadOperator, SpreadProperty: checkSpreadOperator, ExperimentalSpreadProperty: checkSpreadOperator, TemplateLiteral(node) { node.expressions .filter(e => e && hasExcessParens(e)) .forEach(report); }, AssignmentPattern(node) { const { left, right } = node; if (canBeAssignmentTarget(left) && hasExcessParens(left)) { report(left); } if ( right && hasExcessParensWithPrecedence( right, PRECEDENCE_OF_ASSIGNMENT_EXPR, ) ) { report(right); } }, }; }, };