1 | /**
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2 | * @fileoverview Rule to flag statements without curly braces
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3 | * @author Nicholas C. Zakas
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4 | */
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5 | ;
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6 |
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7 | //------------------------------------------------------------------------------
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8 | // Requirements
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9 | //------------------------------------------------------------------------------
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10 |
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11 | const astUtils = require("../ast-utils");
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12 |
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13 | //------------------------------------------------------------------------------
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14 | // Rule Definition
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15 | //------------------------------------------------------------------------------
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16 |
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17 | module.exports = {
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18 | meta: {
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19 | docs: {
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20 | description: "enforce consistent brace style for all control statements",
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21 | category: "Best Practices",
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22 | recommended: false
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23 | },
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24 |
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25 | schema: {
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26 | anyOf: [
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27 | {
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28 | type: "array",
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29 | items: [
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30 | {
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31 | enum: ["all"]
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32 | }
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33 | ],
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34 | minItems: 0,
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35 | maxItems: 1
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36 | },
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37 | {
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38 | type: "array",
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39 | items: [
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40 | {
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41 | enum: ["multi", "multi-line", "multi-or-nest"]
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42 | },
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43 | {
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44 | enum: ["consistent"]
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45 | }
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46 | ],
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47 | minItems: 0,
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48 | maxItems: 2
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49 | }
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50 | ]
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51 | },
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52 |
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53 | fixable: "code"
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54 | },
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55 |
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56 | create(context) {
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57 |
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58 | const multiOnly = (context.options[0] === "multi");
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59 | const multiLine = (context.options[0] === "multi-line");
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60 | const multiOrNest = (context.options[0] === "multi-or-nest");
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61 | const consistent = (context.options[1] === "consistent");
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62 |
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63 | const sourceCode = context.getSourceCode();
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64 |
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65 | //--------------------------------------------------------------------------
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66 | // Helpers
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67 | //--------------------------------------------------------------------------
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68 |
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69 | /**
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70 | * Determines if a given node is a one-liner that's on the same line as it's preceding code.
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71 | * @param {ASTNode} node The node to check.
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72 | * @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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73 | * @private
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74 | */
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75 | function isCollapsedOneLiner(node) {
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76 | const before = sourceCode.getTokenBefore(node);
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77 | const last = sourceCode.getLastToken(node);
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78 | const lastExcludingSemicolon = astUtils.isSemicolonToken(last) ? sourceCode.getTokenBefore(last) : last;
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79 |
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80 | return before.loc.start.line === lastExcludingSemicolon.loc.end.line;
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81 | }
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82 |
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83 | /**
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84 | * Determines if a given node is a one-liner.
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85 | * @param {ASTNode} node The node to check.
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86 | * @returns {boolean} True if the node is a one-liner.
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87 | * @private
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88 | */
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89 | function isOneLiner(node) {
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90 | const first = sourceCode.getFirstToken(node),
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91 | last = sourceCode.getLastToken(node);
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92 |
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93 | return first.loc.start.line === last.loc.end.line;
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94 | }
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95 |
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96 | /**
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97 | * Checks if the given token is an `else` token or not.
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98 | *
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99 | * @param {Token} token - The token to check.
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100 | * @returns {boolean} `true` if the token is an `else` token.
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101 | */
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102 | function isElseKeywordToken(token) {
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103 | return token.value === "else" && token.type === "Keyword";
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104 | }
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105 |
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106 | /**
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107 | * Gets the `else` keyword token of a given `IfStatement` node.
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108 | * @param {ASTNode} node - A `IfStatement` node to get.
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109 | * @returns {Token} The `else` keyword token.
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110 | */
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111 | function getElseKeyword(node) {
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112 | return node.alternate && sourceCode.getFirstTokenBetween(node.consequent, node.alternate, isElseKeywordToken);
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113 | }
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114 |
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115 | /**
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116 | * Checks a given IfStatement node requires braces of the consequent chunk.
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117 | * This returns `true` when below:
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118 | *
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119 | * 1. The given node has the `alternate` node.
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120 | * 2. There is a `IfStatement` which doesn't have `alternate` node in the
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121 | * trailing statement chain of the `consequent` node.
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122 | *
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123 | * @param {ASTNode} node - A IfStatement node to check.
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124 | * @returns {boolean} `true` if the node requires braces of the consequent chunk.
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125 | */
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126 | function requiresBraceOfConsequent(node) {
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127 | if (node.alternate && node.consequent.type === "BlockStatement") {
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128 | if (node.consequent.body.length >= 2) {
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129 | return true;
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130 | }
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131 |
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132 | node = node.consequent.body[0];
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133 | while (node) {
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134 | if (node.type === "IfStatement" && !node.alternate) {
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135 | return true;
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136 | }
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137 | node = astUtils.getTrailingStatement(node);
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138 | }
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139 | }
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140 |
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141 | return false;
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142 | }
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143 |
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144 | /**
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145 | * Reports "Expected { after ..." error
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146 | * @param {ASTNode} node The node to report.
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147 | * @param {ASTNode} bodyNode The body node that is incorrectly missing curly brackets
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148 | * @param {string} name The name to report.
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149 | * @param {string} suffix Additional string to add to the end of a report.
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150 | * @returns {void}
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151 | * @private
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152 | */
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153 | function reportExpectedBraceError(node, bodyNode, name, suffix) {
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154 | context.report({
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155 | node,
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156 | loc: (name !== "else" ? node : getElseKeyword(node)).loc.start,
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157 | message: "Expected { after '{{name}}'{{suffix}}.",
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158 | data: {
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159 | name,
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160 | suffix: (suffix ? ` ${suffix}` : "")
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161 | },
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162 | fix: fixer => fixer.replaceText(bodyNode, `{${sourceCode.getText(bodyNode)}}`)
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163 | });
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164 | }
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165 |
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166 | /**
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167 | * 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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168 | * @param {Token} closingBracket The } token
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169 | * @returns {boolean} `true` if a semicolon needs to be inserted after the last statement in the block.
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170 | */
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171 | function needsSemicolon(closingBracket) {
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172 | const tokenBefore = sourceCode.getTokenBefore(closingBracket);
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173 | const tokenAfter = sourceCode.getTokenAfter(closingBracket);
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174 | const lastBlockNode = sourceCode.getNodeByRangeIndex(tokenBefore.range[0]);
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175 |
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176 | if (astUtils.isSemicolonToken(tokenBefore)) {
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177 |
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178 | // If the last statement already has a semicolon, don't add another one.
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179 | return false;
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180 | }
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181 |
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182 | if (!tokenAfter) {
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183 |
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184 | // If there are no statements after this block, there is no need to add a semicolon.
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185 | return false;
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186 | }
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187 |
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188 | if (lastBlockNode.type === "BlockStatement" && lastBlockNode.parent.type !== "FunctionExpression" && lastBlockNode.parent.type !== "ArrowFunctionExpression") {
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189 |
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190 | // If the last node surrounded by curly brackets is a BlockStatement (other than a FunctionExpression or an ArrowFunctionExpression),
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191 | // don't insert a semicolon. Otherwise, the semicolon would be parsed as a separate statement, which would cause
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192 | // a SyntaxError if it was followed by `else`.
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193 | return false;
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194 | }
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195 |
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196 | if (tokenBefore.loc.end.line === tokenAfter.loc.start.line) {
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197 |
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198 | // If the next token is on the same line, insert a semicolon.
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199 | return true;
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200 | }
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201 |
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202 | if (/^[([/`+-]/.test(tokenAfter.value)) {
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203 |
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204 | // If the next token starts with a character that would disrupt ASI, insert a semicolon.
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205 | return true;
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206 | }
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207 |
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208 | if (tokenBefore.type === "Punctuator" && (tokenBefore.value === "++" || tokenBefore.value === "--")) {
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209 |
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210 | // If the last token is ++ or --, insert a semicolon to avoid disrupting ASI.
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211 | return true;
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212 | }
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213 |
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214 | // Otherwise, do not insert a semicolon.
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215 | return false;
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216 | }
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217 |
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218 | /**
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219 | * Reports "Unnecessary { after ..." error
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220 | * @param {ASTNode} node The node to report.
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221 | * @param {ASTNode} bodyNode The block statement that is incorrectly surrounded by parens
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222 | * @param {string} name The name to report.
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223 | * @param {string} suffix Additional string to add to the end of a report.
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224 | * @returns {void}
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225 | * @private
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226 | */
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227 | function reportUnnecessaryBraceError(node, bodyNode, name, suffix) {
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228 | context.report({
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229 | node,
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230 | loc: (name !== "else" ? node : getElseKeyword(node)).loc.start,
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231 | message: "Unnecessary { after '{{name}}'{{suffix}}.",
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232 | data: {
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233 | name,
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234 | suffix: (suffix ? ` ${suffix}` : "")
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235 | },
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236 | fix(fixer) {
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237 |
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238 | // `do while` expressions sometimes need a space to be inserted after `do`.
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239 | // e.g. `do{foo()} while (bar)` should be corrected to `do foo() while (bar)`
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240 | const needsPrecedingSpace = node.type === "DoWhileStatement" &&
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241 | sourceCode.getTokenBefore(bodyNode).range[1] === bodyNode.range[0] &&
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242 | !astUtils.canTokensBeAdjacent("do", sourceCode.getFirstToken(bodyNode, { skip: 1 }));
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243 |
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244 | const openingBracket = sourceCode.getFirstToken(bodyNode);
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245 | const closingBracket = sourceCode.getLastToken(bodyNode);
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246 | const lastTokenInBlock = sourceCode.getTokenBefore(closingBracket);
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247 |
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248 | if (needsSemicolon(closingBracket)) {
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249 |
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250 | /*
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251 | * If removing braces would cause a SyntaxError due to multiple statements on the same line (or
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252 | * change the semantics of the code due to ASI), don't perform a fix.
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253 | */
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254 | return null;
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255 | }
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256 |
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257 | const resultingBodyText = sourceCode.getText().slice(openingBracket.range[1], lastTokenInBlock.range[0]) +
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258 | sourceCode.getText(lastTokenInBlock) +
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259 | sourceCode.getText().slice(lastTokenInBlock.range[1], closingBracket.range[0]);
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260 |
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261 | return fixer.replaceText(bodyNode, (needsPrecedingSpace ? " " : "") + resultingBodyText);
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262 | }
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263 | });
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264 | }
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265 |
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266 | /**
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267 | * Prepares to check the body of a node to see if it's a block statement.
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268 | * @param {ASTNode} node The node to report if there's a problem.
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269 | * @param {ASTNode} body The body node to check for blocks.
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270 | * @param {string} name The name to report if there's a problem.
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271 | * @param {string} suffix Additional string to add to the end of a report.
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272 | * @returns {Object} a prepared check object, with "actual", "expected", "check" properties.
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273 | * "actual" will be `true` or `false` whether the body is already a block statement.
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274 | * "expected" will be `true` or `false` if the body should be a block statement or not, or
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275 | * `null` if it doesn't matter, depending on the rule options. It can be modified to change
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276 | * the final behavior of "check".
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277 | * "check" will be a function reporting appropriate problems depending on the other
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278 | * properties.
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279 | */
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280 | function prepareCheck(node, body, name, suffix) {
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281 | const hasBlock = (body.type === "BlockStatement");
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282 | let expected = null;
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283 |
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284 | if (node.type === "IfStatement" && node.consequent === body && requiresBraceOfConsequent(node)) {
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285 | expected = true;
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286 | } else if (multiOnly) {
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287 | if (hasBlock && body.body.length === 1) {
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288 | expected = false;
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289 | }
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290 | } else if (multiLine) {
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291 | if (!isCollapsedOneLiner(body)) {
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292 | expected = true;
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293 | }
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294 | } else if (multiOrNest) {
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295 | if (hasBlock && body.body.length === 1 && isOneLiner(body.body[0])) {
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296 | const leadingComments = sourceCode.getCommentsBefore(body.body[0]);
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297 |
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298 | expected = leadingComments.length > 0;
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299 | } else if (!isOneLiner(body)) {
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300 | expected = true;
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301 | }
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302 | } else {
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303 | expected = true;
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304 | }
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305 |
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306 | return {
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307 | actual: hasBlock,
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308 | expected,
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309 | check() {
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310 | if (this.expected !== null && this.expected !== this.actual) {
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311 | if (this.expected) {
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312 | reportExpectedBraceError(node, body, name, suffix);
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313 | } else {
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314 | reportUnnecessaryBraceError(node, body, name, suffix);
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315 | }
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316 | }
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317 | }
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318 | };
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319 | }
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320 |
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321 | /**
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322 | * Prepares to check the bodies of a "if", "else if" and "else" chain.
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323 | * @param {ASTNode} node The first IfStatement node of the chain.
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324 | * @returns {Object[]} prepared checks for each body of the chain. See `prepareCheck` for more
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325 | * information.
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326 | */
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327 | function prepareIfChecks(node) {
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328 | const preparedChecks = [];
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329 |
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330 | do {
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331 | preparedChecks.push(prepareCheck(node, node.consequent, "if", "condition"));
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332 | if (node.alternate && node.alternate.type !== "IfStatement") {
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333 | preparedChecks.push(prepareCheck(node, node.alternate, "else"));
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334 | break;
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335 | }
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336 | node = node.alternate;
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337 | } while (node);
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338 |
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339 | if (consistent) {
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340 |
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341 | /*
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342 | * If any node should have or already have braces, make sure they
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343 | * all have braces.
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344 | * If all nodes shouldn't have braces, make sure they don't.
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345 | */
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346 | const expected = preparedChecks.some(preparedCheck => {
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347 | if (preparedCheck.expected !== null) {
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348 | return preparedCheck.expected;
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349 | }
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350 | return preparedCheck.actual;
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351 | });
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352 |
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353 | preparedChecks.forEach(preparedCheck => {
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354 | preparedCheck.expected = expected;
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355 | });
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356 | }
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357 |
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358 | return preparedChecks;
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359 | }
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360 |
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361 | //--------------------------------------------------------------------------
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362 | // Public
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363 | //--------------------------------------------------------------------------
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364 |
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365 | return {
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366 | IfStatement(node) {
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367 | if (node.parent.type !== "IfStatement") {
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368 | prepareIfChecks(node).forEach(preparedCheck => {
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369 | preparedCheck.check();
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370 | });
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371 | }
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372 | },
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373 |
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374 | WhileStatement(node) {
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375 | prepareCheck(node, node.body, "while", "condition").check();
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376 | },
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377 |
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378 | DoWhileStatement(node) {
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379 | prepareCheck(node, node.body, "do").check();
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380 | },
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381 |
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382 | ForStatement(node) {
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383 | prepareCheck(node, node.body, "for", "condition").check();
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384 | },
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385 |
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386 | ForInStatement(node) {
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387 | prepareCheck(node, node.body, "for-in").check();
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388 | },
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389 |
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390 | ForOfStatement(node) {
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391 | prepareCheck(node, node.body, "for-of").check();
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392 | }
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393 | };
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394 | }
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395 | };
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