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