/** * @fileoverview Rule to flag statements without curly braces * @author Nicholas C. Zakas */ "use strict"; //------------------------------------------------------------------------------ // Requirements //------------------------------------------------------------------------------ const astUtils = require("../ast-utils"); //------------------------------------------------------------------------------ // Rule Definition //------------------------------------------------------------------------------ module.exports = { meta: { docs: { description: "enforce consistent brace style for all control statements", category: "Best Practices", recommended: false, url: "https://eslint.org/docs/rules/curly" }, schema: { anyOf: [ { type: "array", items: [ { enum: ["all"] } ], minItems: 0, maxItems: 1 }, { type: "array", items: [ { enum: ["multi", "multi-line", "multi-or-nest"] }, { enum: ["consistent"] } ], minItems: 0, maxItems: 2 } ] }, fixable: "code", messages: { missingCurlyAfter: "Expected { after '{{name}}'.", missingCurlyAfterCondition: "Expected { after '{{name}}' condition.", unexpectedCurlyAfter: "Unnecessary { after '{{name}}'.", unexpectedCurlyAfterCondition: "Unnecessary { after '{{name}}' condition." } }, create(context) { const multiOnly = (context.options[0] === "multi"); const multiLine = (context.options[0] === "multi-line"); const multiOrNest = (context.options[0] === "multi-or-nest"); const consistent = (context.options[1] === "consistent"); const sourceCode = context.getSourceCode(); //-------------------------------------------------------------------------- // Helpers //-------------------------------------------------------------------------- /** * Determines if a given node is a one-liner that's on the same line as it's preceding code. * @param {ASTNode} node The node to check. * @returns {boolean} True if the node is a one-liner that's on the same line as it's preceding code. * @private */ function isCollapsedOneLiner(node) { const before = sourceCode.getTokenBefore(node); const last = sourceCode.getLastToken(node); const lastExcludingSemicolon = astUtils.isSemicolonToken(last) ? sourceCode.getTokenBefore(last) : last; return before.loc.start.line === lastExcludingSemicolon.loc.end.line; } /** * Determines if a given node is a one-liner. * @param {ASTNode} node The node to check. * @returns {boolean} True if the node is a one-liner. * @private */ function isOneLiner(node) { const first = sourceCode.getFirstToken(node), last = sourceCode.getLastToken(node); return first.loc.start.line === last.loc.end.line; } /** * Checks if the given token is an `else` token or not. * * @param {Token} token - The token to check. * @returns {boolean} `true` if the token is an `else` token. */ function isElseKeywordToken(token) { return token.value === "else" && token.type === "Keyword"; } /** * Gets the `else` keyword token of a given `IfStatement` node. * @param {ASTNode} node - A `IfStatement` node to get. * @returns {Token} The `else` keyword token. */ function getElseKeyword(node) { return node.alternate && sourceCode.getFirstTokenBetween(node.consequent, node.alternate, isElseKeywordToken); } /** * Checks a given IfStatement node requires braces of the consequent chunk. * This returns `true` when below: * * 1. The given node has the `alternate` node. * 2. There is a `IfStatement` which doesn't have `alternate` node in the * trailing statement chain of the `consequent` node. * * @param {ASTNode} node - A IfStatement node to check. * @returns {boolean} `true` if the node requires braces of the consequent chunk. */ function requiresBraceOfConsequent(node) { if (node.alternate && node.consequent.type === "BlockStatement") { if (node.consequent.body.length >= 2) { return true; } for ( let currentNode = node.consequent.body[0]; currentNode; currentNode = astUtils.getTrailingStatement(currentNode) ) { if (currentNode.type === "IfStatement" && !currentNode.alternate) { return true; } } } return false; } /** * Determines if a semicolon needs to be inserted after removing a set of curly brackets, in order to avoid a SyntaxError. * @param {Token} closingBracket The } token * @returns {boolean} `true` if a semicolon needs to be inserted after the last statement in the block. */ function needsSemicolon(closingBracket) { const tokenBefore = sourceCode.getTokenBefore(closingBracket); const tokenAfter = sourceCode.getTokenAfter(closingBracket); const lastBlockNode = sourceCode.getNodeByRangeIndex(tokenBefore.range[0]); if (astUtils.isSemicolonToken(tokenBefore)) { // If the last statement already has a semicolon, don't add another one. return false; } if (!tokenAfter) { // If there are no statements after this block, there is no need to add a semicolon. return false; } if (lastBlockNode.type === "BlockStatement" && lastBlockNode.parent.type !== "FunctionExpression" && lastBlockNode.parent.type !== "ArrowFunctionExpression") { /* * If the last node surrounded by curly brackets is a BlockStatement (other than a FunctionExpression or an ArrowFunctionExpression), * don't insert a semicolon. Otherwise, the semicolon would be parsed as a separate statement, which would cause * a SyntaxError if it was followed by `else`. */ return false; } if (tokenBefore.loc.end.line === tokenAfter.loc.start.line) { // If the next token is on the same line, insert a semicolon. return true; } if (/^[([/`+-]/.test(tokenAfter.value)) { // If the next token starts with a character that would disrupt ASI, insert a semicolon. return true; } if (tokenBefore.type === "Punctuator" && (tokenBefore.value === "++" || tokenBefore.value === "--")) { // If the last token is ++ or --, insert a semicolon to avoid disrupting ASI. return true; } // Otherwise, do not insert a semicolon. return false; } /** * Prepares to check the body of a node to see if it's a block statement. * @param {ASTNode} node The node to report if there's a problem. * @param {ASTNode} body The body node to check for blocks. * @param {string} name The name to report if there's a problem. * @param {{ condition: boolean }} opts Options to pass to the report functions * @returns {Object} a prepared check object, with "actual", "expected", "check" properties. * "actual" will be `true` or `false` whether the body is already a block statement. * "expected" will be `true` or `false` if the body should be a block statement or not, or * `null` if it doesn't matter, depending on the rule options. It can be modified to change * the final behavior of "check". * "check" will be a function reporting appropriate problems depending on the other * properties. */ function prepareCheck(node, body, name, opts) { const hasBlock = (body.type === "BlockStatement"); let expected = null; if (node.type === "IfStatement" && node.consequent === body && requiresBraceOfConsequent(node)) { expected = true; } else if (multiOnly) { if (hasBlock && body.body.length === 1) { expected = false; } } else if (multiLine) { if (!isCollapsedOneLiner(body)) { expected = true; } } else if (multiOrNest) { if (hasBlock && body.body.length === 1 && isOneLiner(body.body[0])) { const leadingComments = sourceCode.getCommentsBefore(body.body[0]); expected = leadingComments.length > 0; } else if (!isOneLiner(body)) { expected = true; } } else { expected = true; } return { actual: hasBlock, expected, check() { if (this.expected !== null && this.expected !== this.actual) { if (this.expected) { context.report({ node, loc: (name !== "else" ? node : getElseKeyword(node)).loc.start, messageId: opts && opts.condition ? "missingCurlyAfterCondition" : "missingCurlyAfter", data: { name }, fix: fixer => fixer.replaceText(body, `{${sourceCode.getText(body)}}`) }); } else { context.report({ node, loc: (name !== "else" ? node : getElseKeyword(node)).loc.start, messageId: opts && opts.condition ? "unexpectedCurlyAfterCondition" : "unexpectedCurlyAfter", data: { name }, fix(fixer) { /* * `do while` expressions sometimes need a space to be inserted after `do`. * e.g. `do{foo()} while (bar)` should be corrected to `do foo() while (bar)` */ const needsPrecedingSpace = node.type === "DoWhileStatement" && sourceCode.getTokenBefore(body).range[1] === body.range[0] && !astUtils.canTokensBeAdjacent("do", sourceCode.getFirstToken(body, { skip: 1 })); const openingBracket = sourceCode.getFirstToken(body); const closingBracket = sourceCode.getLastToken(body); const lastTokenInBlock = sourceCode.getTokenBefore(closingBracket); if (needsSemicolon(closingBracket)) { /* * If removing braces would cause a SyntaxError due to multiple statements on the same line (or * change the semantics of the code due to ASI), don't perform a fix. */ return null; } const resultingBodyText = sourceCode.getText().slice(openingBracket.range[1], lastTokenInBlock.range[0]) + sourceCode.getText(lastTokenInBlock) + sourceCode.getText().slice(lastTokenInBlock.range[1], closingBracket.range[0]); return fixer.replaceText(body, (needsPrecedingSpace ? " " : "") + resultingBodyText); } }); } } } }; } /** * Prepares to check the bodies of a "if", "else if" and "else" chain. * @param {ASTNode} node The first IfStatement node of the chain. * @returns {Object[]} prepared checks for each body of the chain. See `prepareCheck` for more * information. */ function prepareIfChecks(node) { const preparedChecks = []; for (let currentNode = node; currentNode; currentNode = currentNode.alternate) { preparedChecks.push(prepareCheck(currentNode, currentNode.consequent, "if", { condition: true })); if (currentNode.alternate && currentNode.alternate.type !== "IfStatement") { preparedChecks.push(prepareCheck(currentNode, currentNode.alternate, "else")); break; } } if (consistent) { /* * If any node should have or already have braces, make sure they * all have braces. * If all nodes shouldn't have braces, make sure they don't. */ const expected = preparedChecks.some(preparedCheck => { if (preparedCheck.expected !== null) { return preparedCheck.expected; } return preparedCheck.actual; }); preparedChecks.forEach(preparedCheck => { preparedCheck.expected = expected; }); } return preparedChecks; } //-------------------------------------------------------------------------- // Public //-------------------------------------------------------------------------- return { IfStatement(node) { if (node.parent.type !== "IfStatement") { prepareIfChecks(node).forEach(preparedCheck => { preparedCheck.check(); }); } }, WhileStatement(node) { prepareCheck(node, node.body, "while", { condition: true }).check(); }, DoWhileStatement(node) { prepareCheck(node, node.body, "do").check(); }, ForStatement(node) { prepareCheck(node, node.body, "for", { condition: true }).check(); }, ForInStatement(node) { prepareCheck(node, node.body, "for-in").check(); }, ForOfStatement(node) { prepareCheck(node, node.body, "for-of").check(); } }; } };