487 lines
19 KiB
JavaScript
487 lines
19 KiB
JavaScript
/**
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* @fileoverview Rule to flag statements without curly braces
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* @author Nicholas C. Zakas
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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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/** @type {import('../shared/types').Rule} */
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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: "Enforce consistent brace style for all control statements",
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recommended: false,
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url: "https://eslint.org/docs/latest/rules/curly"
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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: ["all"]
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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: ["multi", "multi-line", "multi-or-nest"]
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},
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{
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enum: ["consistent"]
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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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missingCurlyAfter: "Expected { after '{{name}}'.",
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missingCurlyAfterCondition: "Expected { after '{{name}}' condition.",
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unexpectedCurlyAfter: "Unnecessary { after '{{name}}'.",
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unexpectedCurlyAfterCondition: "Unnecessary { after '{{name}}' condition."
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}
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},
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create(context) {
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const multiOnly = (context.options[0] === "multi");
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const multiLine = (context.options[0] === "multi-line");
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const multiOrNest = (context.options[0] === "multi-or-nest");
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const consistent = (context.options[1] === "consistent");
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const sourceCode = context.sourceCode;
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//--------------------------------------------------------------------------
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// Helpers
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//--------------------------------------------------------------------------
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/**
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* Determines if a given node is a one-liner that's on the same line as it's preceding code.
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* @param {ASTNode} node The node to check.
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* @returns {boolean} True if the node is a one-liner that's on the same line as it's preceding code.
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* @private
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*/
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function isCollapsedOneLiner(node) {
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const before = sourceCode.getTokenBefore(node);
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const last = sourceCode.getLastToken(node);
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const lastExcludingSemicolon = astUtils.isSemicolonToken(last) ? sourceCode.getTokenBefore(last) : last;
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return before.loc.start.line === lastExcludingSemicolon.loc.end.line;
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}
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/**
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* Determines if a given node is a one-liner.
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* @param {ASTNode} node The node to check.
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* @returns {boolean} True if the node is a one-liner.
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* @private
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*/
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function isOneLiner(node) {
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if (node.type === "EmptyStatement") {
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return true;
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}
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const first = sourceCode.getFirstToken(node);
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const last = sourceCode.getLastToken(node);
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const lastExcludingSemicolon = astUtils.isSemicolonToken(last) ? sourceCode.getTokenBefore(last) : last;
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return first.loc.start.line === lastExcludingSemicolon.loc.end.line;
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}
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/**
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* Determines if the given node is a lexical declaration (let, const, function, or class)
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* @param {ASTNode} node The node to check
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* @returns {boolean} True if the node is a lexical declaration
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* @private
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*/
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function isLexicalDeclaration(node) {
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if (node.type === "VariableDeclaration") {
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return node.kind === "const" || node.kind === "let";
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}
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return node.type === "FunctionDeclaration" || node.type === "ClassDeclaration";
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}
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/**
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* Checks if the given token is an `else` token or not.
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* @param {Token} token The token to check.
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* @returns {boolean} `true` if the token is an `else` token.
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*/
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function isElseKeywordToken(token) {
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return token.value === "else" && token.type === "Keyword";
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}
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/**
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* Determines whether the given node has an `else` keyword token as the first token after.
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* @param {ASTNode} node The node to check.
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* @returns {boolean} `true` if the node is followed by an `else` keyword token.
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*/
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function isFollowedByElseKeyword(node) {
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const nextToken = sourceCode.getTokenAfter(node);
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return Boolean(nextToken) && isElseKeywordToken(nextToken);
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}
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/**
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* Determines if a semicolon needs to be inserted after removing a set of curly brackets, in order to avoid a SyntaxError.
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* @param {Token} closingBracket The } token
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* @returns {boolean} `true` if a semicolon needs to be inserted after the last statement in the block.
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*/
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function needsSemicolon(closingBracket) {
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const tokenBefore = sourceCode.getTokenBefore(closingBracket);
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const tokenAfter = sourceCode.getTokenAfter(closingBracket);
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const lastBlockNode = sourceCode.getNodeByRangeIndex(tokenBefore.range[0]);
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if (astUtils.isSemicolonToken(tokenBefore)) {
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// If the last statement already has a semicolon, don't add another one.
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return false;
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}
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if (!tokenAfter) {
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// If there are no statements after this block, there is no need to add a semicolon.
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return false;
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}
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if (lastBlockNode.type === "BlockStatement" && lastBlockNode.parent.type !== "FunctionExpression" && lastBlockNode.parent.type !== "ArrowFunctionExpression") {
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/*
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* If the last node surrounded by curly brackets is a BlockStatement (other than a FunctionExpression or an ArrowFunctionExpression),
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* don't insert a semicolon. Otherwise, the semicolon would be parsed as a separate statement, which would cause
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* a SyntaxError if it was followed by `else`.
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*/
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return false;
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}
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if (tokenBefore.loc.end.line === tokenAfter.loc.start.line) {
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// If the next token is on the same line, insert a semicolon.
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return true;
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}
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if (/^[([/`+-]/u.test(tokenAfter.value)) {
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// If the next token starts with a character that would disrupt ASI, insert a semicolon.
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return true;
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}
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if (tokenBefore.type === "Punctuator" && (tokenBefore.value === "++" || tokenBefore.value === "--")) {
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// If the last token is ++ or --, insert a semicolon to avoid disrupting ASI.
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return true;
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}
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// Otherwise, do not insert a semicolon.
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return false;
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}
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/**
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* Determines whether the code represented by the given node contains an `if` statement
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* that would become associated with an `else` keyword directly appended to that code.
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*
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* Examples where it returns `true`:
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*
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* if (a)
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* foo();
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*
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* if (a) {
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* foo();
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* }
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*
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* if (a)
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* foo();
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* else if (b)
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* bar();
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*
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* while (a)
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* if (b)
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* if(c)
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* foo();
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* else
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* bar();
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*
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* Examples where it returns `false`:
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*
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* if (a)
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* foo();
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* else
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* bar();
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*
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* while (a) {
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* if (b)
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* if(c)
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* foo();
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* else
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* bar();
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* }
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*
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* while (a)
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* if (b) {
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* if(c)
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* foo();
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* }
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* else
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* bar();
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* @param {ASTNode} node Node representing the code to check.
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* @returns {boolean} `true` if an `if` statement within the code would become associated with an `else` appended to that code.
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*/
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function hasUnsafeIf(node) {
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switch (node.type) {
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case "IfStatement":
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if (!node.alternate) {
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return true;
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}
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return hasUnsafeIf(node.alternate);
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case "ForStatement":
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case "ForInStatement":
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case "ForOfStatement":
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case "LabeledStatement":
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case "WithStatement":
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case "WhileStatement":
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return hasUnsafeIf(node.body);
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default:
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return false;
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}
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}
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/**
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* Determines whether the existing curly braces around the single statement are necessary to preserve the semantics of the code.
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* The braces, which make the given block body, are necessary in either of the following situations:
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*
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* 1. The statement is a lexical declaration.
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* 2. Without the braces, an `if` within the statement would become associated with an `else` after the closing brace:
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*
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* if (a) {
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* if (b)
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* foo();
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* }
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* else
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* bar();
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*
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* if (a)
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* while (b)
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* while (c) {
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* while (d)
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* if (e)
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* while(f)
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* foo();
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* }
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* else
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* bar();
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* @param {ASTNode} node `BlockStatement` body with exactly one statement directly inside. The statement can have its own nested statements.
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* @returns {boolean} `true` if the braces are necessary - removing them (replacing the given `BlockStatement` body with its single statement content)
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* would change the semantics of the code or produce a syntax error.
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*/
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function areBracesNecessary(node) {
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const statement = node.body[0];
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return isLexicalDeclaration(statement) ||
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hasUnsafeIf(statement) && isFollowedByElseKeyword(node);
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}
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/**
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* Prepares to check the body of a node to see if it's a block statement.
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* @param {ASTNode} node The node to report if there's a problem.
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* @param {ASTNode} body The body node to check for blocks.
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* @param {string} name The name to report if there's a problem.
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* @param {{ condition: boolean }} opts Options to pass to the report functions
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* @returns {Object} a prepared check object, with "actual", "expected", "check" properties.
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* "actual" will be `true` or `false` whether the body is already a block statement.
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* "expected" will be `true` or `false` if the body should be a block statement or not, or
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* `null` if it doesn't matter, depending on the rule options. It can be modified to change
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* the final behavior of "check".
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* "check" will be a function reporting appropriate problems depending on the other
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* properties.
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*/
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function prepareCheck(node, body, name, opts) {
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const hasBlock = (body.type === "BlockStatement");
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let expected = null;
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if (hasBlock && (body.body.length !== 1 || areBracesNecessary(body))) {
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expected = true;
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} else if (multiOnly) {
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expected = false;
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} else if (multiLine) {
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if (!isCollapsedOneLiner(body)) {
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expected = true;
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}
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// otherwise, the body is allowed to have braces or not to have braces
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} else if (multiOrNest) {
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if (hasBlock) {
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const statement = body.body[0];
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const leadingCommentsInBlock = sourceCode.getCommentsBefore(statement);
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expected = !isOneLiner(statement) || leadingCommentsInBlock.length > 0;
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} else {
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expected = !isOneLiner(body);
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}
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} else {
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// default "all"
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expected = true;
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}
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return {
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actual: hasBlock,
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expected,
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check() {
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if (this.expected !== null && this.expected !== this.actual) {
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if (this.expected) {
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context.report({
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node,
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loc: body.loc,
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messageId: opts && opts.condition ? "missingCurlyAfterCondition" : "missingCurlyAfter",
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data: {
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name
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},
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fix: fixer => fixer.replaceText(body, `{${sourceCode.getText(body)}}`)
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});
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} else {
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context.report({
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node,
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loc: body.loc,
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messageId: opts && opts.condition ? "unexpectedCurlyAfterCondition" : "unexpectedCurlyAfter",
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data: {
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name
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},
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fix(fixer) {
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/*
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* `do while` expressions sometimes need a space to be inserted after `do`.
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* e.g. `do{foo()} while (bar)` should be corrected to `do foo() while (bar)`
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*/
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const needsPrecedingSpace = node.type === "DoWhileStatement" &&
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sourceCode.getTokenBefore(body).range[1] === body.range[0] &&
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!astUtils.canTokensBeAdjacent("do", sourceCode.getFirstToken(body, { skip: 1 }));
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const openingBracket = sourceCode.getFirstToken(body);
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const closingBracket = sourceCode.getLastToken(body);
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const lastTokenInBlock = sourceCode.getTokenBefore(closingBracket);
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if (needsSemicolon(closingBracket)) {
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/*
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* If removing braces would cause a SyntaxError due to multiple statements on the same line (or
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* change the semantics of the code due to ASI), don't perform a fix.
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*/
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return null;
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}
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const resultingBodyText = sourceCode.getText().slice(openingBracket.range[1], lastTokenInBlock.range[0]) +
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sourceCode.getText(lastTokenInBlock) +
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sourceCode.getText().slice(lastTokenInBlock.range[1], closingBracket.range[0]);
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return fixer.replaceText(body, (needsPrecedingSpace ? " " : "") + resultingBodyText);
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}
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});
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}
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}
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}
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};
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}
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/**
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* Prepares to check the bodies of a "if", "else if" and "else" chain.
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* @param {ASTNode} node The first IfStatement node of the chain.
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* @returns {Object[]} prepared checks for each body of the chain. See `prepareCheck` for more
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* information.
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*/
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function prepareIfChecks(node) {
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const preparedChecks = [];
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for (let currentNode = node; currentNode; currentNode = currentNode.alternate) {
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preparedChecks.push(prepareCheck(currentNode, currentNode.consequent, "if", { condition: true }));
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if (currentNode.alternate && currentNode.alternate.type !== "IfStatement") {
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preparedChecks.push(prepareCheck(currentNode, currentNode.alternate, "else"));
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break;
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}
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}
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if (consistent) {
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/*
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* If any node should have or already have braces, make sure they
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* all have braces.
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* If all nodes shouldn't have braces, make sure they don't.
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*/
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const expected = preparedChecks.some(preparedCheck => {
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if (preparedCheck.expected !== null) {
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return preparedCheck.expected;
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}
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return preparedCheck.actual;
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});
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preparedChecks.forEach(preparedCheck => {
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preparedCheck.expected = expected;
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});
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}
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return preparedChecks;
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}
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//--------------------------------------------------------------------------
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// Public
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//--------------------------------------------------------------------------
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return {
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IfStatement(node) {
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const parent = node.parent;
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const isElseIf = parent.type === "IfStatement" && parent.alternate === node;
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if (!isElseIf) {
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// This is a top `if`, check the whole `if-else-if` chain
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prepareIfChecks(node).forEach(preparedCheck => {
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preparedCheck.check();
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});
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}
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// Skip `else if`, it's already checked (when the top `if` was visited)
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},
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WhileStatement(node) {
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prepareCheck(node, node.body, "while", { condition: true }).check();
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},
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DoWhileStatement(node) {
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prepareCheck(node, node.body, "do").check();
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},
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ForStatement(node) {
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prepareCheck(node, node.body, "for", { condition: true }).check();
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},
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ForInStatement(node) {
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prepareCheck(node, node.body, "for-in").check();
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},
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ForOfStatement(node) {
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prepareCheck(node, node.body, "for-of").check();
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}
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};
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}
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};
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