1 | /**
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2 | * @fileoverview Rule to flag trailing underscores in variable declarations.
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3 | * @author Matt DuVall <http://www.mattduvall.com>
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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 | //------------------------------------------------------------------------------
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9 | // Rule Definition
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10 | //------------------------------------------------------------------------------
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11 |
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12 | module.exports = {
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13 | meta: {
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14 | docs: {
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15 | description: "disallow dangling underscores in identifiers",
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16 | category: "Stylistic Issues",
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17 | recommended: false,
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18 | url: "https://eslint.org/docs/rules/no-underscore-dangle"
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19 | },
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20 |
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21 | schema: [
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22 | {
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23 | type: "object",
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24 | properties: {
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25 | allow: {
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26 | type: "array",
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27 | items: {
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28 | type: "string"
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29 | }
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30 | },
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31 | allowAfterThis: {
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32 | type: "boolean"
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33 | },
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34 | allowAfterSuper: {
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35 | type: "boolean"
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36 | },
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37 | enforceInMethodNames: {
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38 | type: "boolean"
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39 | }
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40 | },
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41 | additionalProperties: false
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42 | }
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43 | ]
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44 | },
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45 |
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46 | create(context) {
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47 |
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48 | const options = context.options[0] || {};
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49 | const ALLOWED_VARIABLES = options.allow ? options.allow : [];
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50 | const allowAfterThis = typeof options.allowAfterThis !== "undefined" ? options.allowAfterThis : false;
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51 | const allowAfterSuper = typeof options.allowAfterSuper !== "undefined" ? options.allowAfterSuper : false;
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52 | const enforceInMethodNames = typeof options.enforceInMethodNames !== "undefined" ? options.enforceInMethodNames : false;
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53 |
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54 | //-------------------------------------------------------------------------
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55 | // Helpers
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56 | //-------------------------------------------------------------------------
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57 |
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58 | /**
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59 | * Check if identifier is present inside the allowed option
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60 | * @param {string} identifier name of the node
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61 | * @returns {boolean} true if its is present
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62 | * @private
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63 | */
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64 | function isAllowed(identifier) {
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65 | return ALLOWED_VARIABLES.some(ident => ident === identifier);
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66 | }
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67 |
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68 | /**
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69 | * Check if identifier has a underscore at the end
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70 | * @param {ASTNode} identifier node to evaluate
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71 | * @returns {boolean} true if its is present
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72 | * @private
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73 | */
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74 | function hasTrailingUnderscore(identifier) {
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75 | const len = identifier.length;
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76 |
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77 | return identifier !== "_" && (identifier[0] === "_" || identifier[len - 1] === "_");
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78 | }
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79 |
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80 | /**
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81 | * Check if identifier is a special case member expression
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82 | * @param {ASTNode} identifier node to evaluate
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83 | * @returns {boolean} true if its is a special case
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84 | * @private
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85 | */
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86 | function isSpecialCaseIdentifierForMemberExpression(identifier) {
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87 | return identifier === "__proto__";
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88 | }
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89 |
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90 | /**
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91 | * Check if identifier is a special case variable expression
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92 | * @param {ASTNode} identifier node to evaluate
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93 | * @returns {boolean} true if its is a special case
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94 | * @private
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95 | */
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96 | function isSpecialCaseIdentifierInVariableExpression(identifier) {
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97 |
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98 | // Checks for the underscore library usage here
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99 | return identifier === "_";
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100 | }
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101 |
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102 | /**
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103 | * Check if function has a underscore at the end
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104 | * @param {ASTNode} node node to evaluate
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105 | * @returns {void}
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106 | * @private
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107 | */
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108 | function checkForTrailingUnderscoreInFunctionDeclaration(node) {
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109 | if (node.id) {
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110 | const identifier = node.id.name;
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111 |
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112 | if (typeof identifier !== "undefined" && hasTrailingUnderscore(identifier) && !isAllowed(identifier)) {
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113 | context.report({
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114 | node,
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115 | message: "Unexpected dangling '_' in '{{identifier}}'.",
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116 | data: {
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117 | identifier
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118 | }
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119 | });
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120 | }
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121 | }
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122 | }
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123 |
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124 | /**
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125 | * Check if variable expression has a underscore at the end
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126 | * @param {ASTNode} node node to evaluate
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127 | * @returns {void}
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128 | * @private
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129 | */
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130 | function checkForTrailingUnderscoreInVariableExpression(node) {
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131 | const identifier = node.id.name;
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132 |
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133 | if (typeof identifier !== "undefined" && hasTrailingUnderscore(identifier) &&
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134 | !isSpecialCaseIdentifierInVariableExpression(identifier) && !isAllowed(identifier)) {
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135 | context.report({
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136 | node,
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137 | message: "Unexpected dangling '_' in '{{identifier}}'.",
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138 | data: {
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139 | identifier
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140 | }
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141 | });
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142 | }
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143 | }
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144 |
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145 | /**
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146 | * Check if member expression has a underscore at the end
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147 | * @param {ASTNode} node node to evaluate
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148 | * @returns {void}
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149 | * @private
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150 | */
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151 | function checkForTrailingUnderscoreInMemberExpression(node) {
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152 | const identifier = node.property.name,
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153 | isMemberOfThis = node.object.type === "ThisExpression",
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154 | isMemberOfSuper = node.object.type === "Super";
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155 |
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156 | if (typeof identifier !== "undefined" && hasTrailingUnderscore(identifier) &&
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157 | !(isMemberOfThis && allowAfterThis) &&
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158 | !(isMemberOfSuper && allowAfterSuper) &&
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159 | !isSpecialCaseIdentifierForMemberExpression(identifier) && !isAllowed(identifier)) {
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160 | context.report({
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161 | node,
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162 | message: "Unexpected dangling '_' in '{{identifier}}'.",
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163 | data: {
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164 | identifier
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165 | }
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166 | });
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167 | }
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168 | }
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169 |
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170 | /**
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171 | * Check if method declaration or method property has a underscore at the end
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172 | * @param {ASTNode} node node to evaluate
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173 | * @returns {void}
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174 | * @private
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175 | */
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176 | function checkForTrailingUnderscoreInMethod(node) {
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177 | const identifier = node.key.name;
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178 | const isMethod = node.type === "MethodDefinition" || node.type === "Property" && node.method;
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179 |
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180 | if (typeof identifier !== "undefined" && enforceInMethodNames && isMethod && hasTrailingUnderscore(identifier)) {
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181 | context.report({
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182 | node,
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183 | message: "Unexpected dangling '_' in '{{identifier}}'.",
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184 | data: {
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185 | identifier
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186 | }
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187 | });
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188 | }
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189 | }
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190 |
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191 | //--------------------------------------------------------------------------
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192 | // Public API
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193 | //--------------------------------------------------------------------------
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194 |
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195 | return {
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196 | FunctionDeclaration: checkForTrailingUnderscoreInFunctionDeclaration,
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197 | VariableDeclarator: checkForTrailingUnderscoreInVariableExpression,
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198 | MemberExpression: checkForTrailingUnderscoreInMemberExpression,
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199 | MethodDefinition: checkForTrailingUnderscoreInMethod,
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200 | Property: checkForTrailingUnderscoreInMethod
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201 | };
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202 |
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203 | }
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204 | };
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