1 | /*
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2 | MIT License http://www.opensource.org/licenses/mit-license.php
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3 | Author Tobias Koppers @sokra
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4 | */
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5 |
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6 | "use strict";
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7 |
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8 | const CachedConstDependency = require("./dependencies/CachedConstDependency");
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9 | const ConstDependency = require("./dependencies/ConstDependency");
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10 | const { evaluateToString } = require("./javascript/JavascriptParserHelpers");
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11 | const { parseResource } = require("./util/identifier");
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12 |
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13 | /** @typedef {import("estree").Expression} ExpressionNode */
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14 | /** @typedef {import("estree").Super} SuperNode */
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15 | /** @typedef {import("./Compiler")} Compiler */
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16 |
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17 | const collectDeclaration = (declarations, pattern) => {
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18 | const stack = [pattern];
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19 | while (stack.length > 0) {
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20 | const node = stack.pop();
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21 | switch (node.type) {
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22 | case "Identifier":
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23 | declarations.add(node.name);
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24 | break;
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25 | case "ArrayPattern":
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26 | for (const element of node.elements) {
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27 | if (element) {
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28 | stack.push(element);
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29 | }
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30 | }
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31 | break;
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32 | case "AssignmentPattern":
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33 | stack.push(node.left);
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34 | break;
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35 | case "ObjectPattern":
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36 | for (const property of node.properties) {
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37 | stack.push(property.value);
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38 | }
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39 | break;
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40 | case "RestElement":
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41 | stack.push(node.argument);
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42 | break;
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43 | }
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44 | }
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45 | };
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46 |
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47 | const getHoistedDeclarations = (branch, includeFunctionDeclarations) => {
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48 | const declarations = new Set();
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49 | const stack = [branch];
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50 | while (stack.length > 0) {
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51 | const node = stack.pop();
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52 | // Some node could be `null` or `undefined`.
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53 | if (!node) continue;
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54 | switch (node.type) {
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55 | // Walk through control statements to look for hoisted declarations.
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56 | // Some branches are skipped since they do not allow declarations.
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57 | case "BlockStatement":
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58 | for (const stmt of node.body) {
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59 | stack.push(stmt);
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60 | }
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61 | break;
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62 | case "IfStatement":
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63 | stack.push(node.consequent);
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64 | stack.push(node.alternate);
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65 | break;
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66 | case "ForStatement":
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67 | stack.push(node.init);
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68 | stack.push(node.body);
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69 | break;
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70 | case "ForInStatement":
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71 | case "ForOfStatement":
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72 | stack.push(node.left);
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73 | stack.push(node.body);
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74 | break;
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75 | case "DoWhileStatement":
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76 | case "WhileStatement":
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77 | case "LabeledStatement":
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78 | stack.push(node.body);
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79 | break;
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80 | case "SwitchStatement":
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81 | for (const cs of node.cases) {
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82 | for (const consequent of cs.consequent) {
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83 | stack.push(consequent);
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84 | }
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85 | }
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86 | break;
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87 | case "TryStatement":
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88 | stack.push(node.block);
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89 | if (node.handler) {
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90 | stack.push(node.handler.body);
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91 | }
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92 | stack.push(node.finalizer);
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93 | break;
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94 | case "FunctionDeclaration":
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95 | if (includeFunctionDeclarations) {
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96 | collectDeclaration(declarations, node.id);
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97 | }
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98 | break;
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99 | case "VariableDeclaration":
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100 | if (node.kind === "var") {
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101 | for (const decl of node.declarations) {
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102 | collectDeclaration(declarations, decl.id);
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103 | }
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104 | }
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105 | break;
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106 | }
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107 | }
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108 | return Array.from(declarations);
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109 | };
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110 |
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111 | class ConstPlugin {
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112 | /**
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113 | * Apply the plugin
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114 | * @param {Compiler} compiler the compiler instance
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115 | * @returns {void}
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116 | */
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117 | apply(compiler) {
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118 | const cachedParseResource = parseResource.bindCache(compiler.root);
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119 | compiler.hooks.compilation.tap(
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120 | "ConstPlugin",
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121 | (compilation, { normalModuleFactory }) => {
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122 | compilation.dependencyTemplates.set(
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123 | ConstDependency,
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124 | new ConstDependency.Template()
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125 | );
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126 |
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127 | compilation.dependencyTemplates.set(
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128 | CachedConstDependency,
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129 | new CachedConstDependency.Template()
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130 | );
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131 |
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132 | const handler = parser => {
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133 | parser.hooks.statementIf.tap("ConstPlugin", statement => {
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134 | if (parser.scope.isAsmJs) return;
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135 | const param = parser.evaluateExpression(statement.test);
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136 | const bool = param.asBool();
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137 | if (typeof bool === "boolean") {
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138 | if (!param.couldHaveSideEffects()) {
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139 | const dep = new ConstDependency(`${bool}`, param.range);
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140 | dep.loc = statement.loc;
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141 | parser.state.module.addPresentationalDependency(dep);
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142 | } else {
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143 | parser.walkExpression(statement.test);
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144 | }
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145 | const branchToRemove = bool
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146 | ? statement.alternate
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147 | : statement.consequent;
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148 | if (branchToRemove) {
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149 | // Before removing the dead branch, the hoisted declarations
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150 | // must be collected.
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151 | //
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152 | // Given the following code:
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153 | //
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154 | // if (true) f() else g()
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155 | // if (false) {
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156 | // function f() {}
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157 | // const g = function g() {}
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158 | // if (someTest) {
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159 | // let a = 1
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160 | // var x, {y, z} = obj
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161 | // }
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162 | // } else {
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163 | // …
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164 | // }
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165 | //
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166 | // the generated code is:
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167 | //
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168 | // if (true) f() else {}
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169 | // if (false) {
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170 | // var f, x, y, z; (in loose mode)
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171 | // var x, y, z; (in strict mode)
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172 | // } else {
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173 | // …
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174 | // }
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175 | //
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176 | // NOTE: When code runs in strict mode, `var` declarations
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177 | // are hoisted but `function` declarations don't.
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178 | //
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179 | let declarations;
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180 | if (parser.scope.isStrict) {
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181 | // If the code runs in strict mode, variable declarations
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182 | // using `var` must be hoisted.
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183 | declarations = getHoistedDeclarations(branchToRemove, false);
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184 | } else {
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185 | // Otherwise, collect all hoisted declaration.
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186 | declarations = getHoistedDeclarations(branchToRemove, true);
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187 | }
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188 | let replacement;
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189 | if (declarations.length > 0) {
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190 | replacement = `{ var ${declarations.join(", ")}; }`;
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191 | } else {
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192 | replacement = "{}";
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193 | }
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194 | const dep = new ConstDependency(
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195 | replacement,
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196 | branchToRemove.range
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197 | );
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198 | dep.loc = branchToRemove.loc;
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199 | parser.state.module.addPresentationalDependency(dep);
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200 | }
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201 | return bool;
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202 | }
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203 | });
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204 | parser.hooks.expressionConditionalOperator.tap(
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205 | "ConstPlugin",
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206 | expression => {
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207 | if (parser.scope.isAsmJs) return;
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208 | const param = parser.evaluateExpression(expression.test);
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209 | const bool = param.asBool();
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210 | if (typeof bool === "boolean") {
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211 | if (!param.couldHaveSideEffects()) {
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212 | const dep = new ConstDependency(` ${bool}`, param.range);
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213 | dep.loc = expression.loc;
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214 | parser.state.module.addPresentationalDependency(dep);
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215 | } else {
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216 | parser.walkExpression(expression.test);
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217 | }
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218 | // Expressions do not hoist.
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219 | // It is safe to remove the dead branch.
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220 | //
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221 | // Given the following code:
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222 | //
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223 | // false ? someExpression() : otherExpression();
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224 | //
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225 | // the generated code is:
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226 | //
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227 | // false ? 0 : otherExpression();
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228 | //
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229 | const branchToRemove = bool
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230 | ? expression.alternate
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231 | : expression.consequent;
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232 | const dep = new ConstDependency("0", branchToRemove.range);
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233 | dep.loc = branchToRemove.loc;
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234 | parser.state.module.addPresentationalDependency(dep);
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235 | return bool;
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236 | }
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237 | }
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238 | );
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239 | parser.hooks.expressionLogicalOperator.tap(
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240 | "ConstPlugin",
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241 | expression => {
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242 | if (parser.scope.isAsmJs) return;
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243 | if (
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244 | expression.operator === "&&" ||
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245 | expression.operator === "||"
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246 | ) {
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247 | const param = parser.evaluateExpression(expression.left);
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248 | const bool = param.asBool();
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249 | if (typeof bool === "boolean") {
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250 | // Expressions do not hoist.
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251 | // It is safe to remove the dead branch.
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252 | //
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253 | // ------------------------------------------
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254 | //
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255 | // Given the following code:
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256 | //
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257 | // falsyExpression() && someExpression();
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258 | //
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259 | // the generated code is:
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260 | //
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261 | // falsyExpression() && false;
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262 | //
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263 | // ------------------------------------------
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264 | //
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265 | // Given the following code:
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266 | //
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267 | // truthyExpression() && someExpression();
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268 | //
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269 | // the generated code is:
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270 | //
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271 | // true && someExpression();
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272 | //
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273 | // ------------------------------------------
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274 | //
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275 | // Given the following code:
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276 | //
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277 | // truthyExpression() || someExpression();
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278 | //
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279 | // the generated code is:
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280 | //
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281 | // truthyExpression() || false;
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282 | //
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283 | // ------------------------------------------
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284 | //
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285 | // Given the following code:
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286 | //
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287 | // falsyExpression() || someExpression();
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288 | //
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289 | // the generated code is:
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290 | //
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291 | // false && someExpression();
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292 | //
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293 | const keepRight =
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294 | (expression.operator === "&&" && bool) ||
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295 | (expression.operator === "||" && !bool);
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296 |
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297 | if (
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298 | !param.couldHaveSideEffects() &&
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299 | (param.isBoolean() || keepRight)
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300 | ) {
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301 | // for case like
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302 | //
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303 | // return'development'===process.env.NODE_ENV&&'foo'
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304 | //
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305 | // we need a space before the bool to prevent result like
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306 | //
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307 | // returnfalse&&'foo'
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308 | //
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309 | const dep = new ConstDependency(` ${bool}`, param.range);
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310 | dep.loc = expression.loc;
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311 | parser.state.module.addPresentationalDependency(dep);
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312 | } else {
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313 | parser.walkExpression(expression.left);
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314 | }
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315 | if (!keepRight) {
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316 | const dep = new ConstDependency(
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317 | "0",
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318 | expression.right.range
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319 | );
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320 | dep.loc = expression.loc;
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321 | parser.state.module.addPresentationalDependency(dep);
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322 | }
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323 | return keepRight;
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324 | }
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325 | } else if (expression.operator === "??") {
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326 | const param = parser.evaluateExpression(expression.left);
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327 | const keepRight = param && param.asNullish();
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328 | if (typeof keepRight === "boolean") {
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329 | // ------------------------------------------
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330 | //
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331 | // Given the following code:
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332 | //
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333 | // nonNullish ?? someExpression();
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334 | //
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335 | // the generated code is:
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336 | //
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337 | // nonNullish ?? 0;
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338 | //
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339 | // ------------------------------------------
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340 | //
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341 | // Given the following code:
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342 | //
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343 | // nullish ?? someExpression();
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344 | //
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345 | // the generated code is:
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346 | //
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347 | // null ?? someExpression();
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348 | //
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349 | if (!param.couldHaveSideEffects() && keepRight) {
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350 | // cspell:word returnnull
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351 | // for case like
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352 | //
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353 | // return('development'===process.env.NODE_ENV&&null)??'foo'
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354 | //
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355 | // we need a space before the bool to prevent result like
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356 | //
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357 | // returnnull??'foo'
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358 | //
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359 | const dep = new ConstDependency(" null", param.range);
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360 | dep.loc = expression.loc;
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361 | parser.state.module.addPresentationalDependency(dep);
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362 | } else {
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363 | const dep = new ConstDependency(
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364 | "0",
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365 | expression.right.range
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366 | );
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367 | dep.loc = expression.loc;
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368 | parser.state.module.addPresentationalDependency(dep);
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369 | parser.walkExpression(expression.left);
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370 | }
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371 |
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372 | return keepRight;
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373 | }
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374 | }
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375 | }
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376 | );
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377 | parser.hooks.optionalChaining.tap("ConstPlugin", expr => {
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378 | /** @type {ExpressionNode[]} */
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379 | const optionalExpressionsStack = [];
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380 | /** @type {ExpressionNode|SuperNode} */
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381 | let next = expr.expression;
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382 |
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383 | while (
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384 | next.type === "MemberExpression" ||
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385 | next.type === "CallExpression"
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386 | ) {
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387 | if (next.type === "MemberExpression") {
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388 | if (next.optional) {
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389 | // SuperNode can not be optional
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390 | optionalExpressionsStack.push(
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391 | /** @type {ExpressionNode} */ (next.object)
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392 | );
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393 | }
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394 | next = next.object;
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395 | } else {
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396 | if (next.optional) {
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397 | // SuperNode can not be optional
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398 | optionalExpressionsStack.push(
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399 | /** @type {ExpressionNode} */ (next.callee)
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400 | );
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401 | }
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402 | next = next.callee;
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403 | }
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404 | }
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405 |
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406 | while (optionalExpressionsStack.length) {
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407 | const expression = optionalExpressionsStack.pop();
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408 | const evaluated = parser.evaluateExpression(expression);
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409 |
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410 | if (evaluated && evaluated.asNullish()) {
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411 | // ------------------------------------------
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412 | //
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413 | // Given the following code:
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414 | //
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415 | // nullishMemberChain?.a.b();
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416 | //
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417 | // the generated code is:
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418 | //
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419 | // undefined;
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420 | //
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421 | // ------------------------------------------
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422 | //
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423 | const dep = new ConstDependency(" undefined", expr.range);
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424 | dep.loc = expr.loc;
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425 | parser.state.module.addPresentationalDependency(dep);
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426 | return true;
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427 | }
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428 | }
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429 | });
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430 | parser.hooks.evaluateIdentifier
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431 | .for("__resourceQuery")
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432 | .tap("ConstPlugin", expr => {
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433 | if (parser.scope.isAsmJs) return;
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434 | if (!parser.state.module) return;
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435 | return evaluateToString(
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436 | cachedParseResource(parser.state.module.resource).query
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437 | )(expr);
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438 | });
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439 | parser.hooks.expression
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440 | .for("__resourceQuery")
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441 | .tap("ConstPlugin", expr => {
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442 | if (parser.scope.isAsmJs) return;
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443 | if (!parser.state.module) return;
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444 | const dep = new CachedConstDependency(
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445 | JSON.stringify(
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446 | cachedParseResource(parser.state.module.resource).query
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447 | ),
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448 | expr.range,
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449 | "__resourceQuery"
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450 | );
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451 | dep.loc = expr.loc;
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452 | parser.state.module.addPresentationalDependency(dep);
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453 | return true;
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454 | });
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455 |
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456 | parser.hooks.evaluateIdentifier
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457 | .for("__resourceFragment")
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458 | .tap("ConstPlugin", expr => {
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459 | if (parser.scope.isAsmJs) return;
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460 | if (!parser.state.module) return;
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461 | return evaluateToString(
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462 | cachedParseResource(parser.state.module.resource).fragment
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463 | )(expr);
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464 | });
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465 | parser.hooks.expression
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466 | .for("__resourceFragment")
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467 | .tap("ConstPlugin", expr => {
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468 | if (parser.scope.isAsmJs) return;
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469 | if (!parser.state.module) return;
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470 | const dep = new CachedConstDependency(
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471 | JSON.stringify(
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472 | cachedParseResource(parser.state.module.resource).fragment
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473 | ),
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474 | expr.range,
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475 | "__resourceFragment"
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476 | );
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477 | dep.loc = expr.loc;
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478 | parser.state.module.addPresentationalDependency(dep);
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479 | return true;
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480 | });
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481 | };
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482 |
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483 | normalModuleFactory.hooks.parser
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484 | .for("javascript/auto")
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485 | .tap("ConstPlugin", handler);
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486 | normalModuleFactory.hooks.parser
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487 | .for("javascript/dynamic")
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488 | .tap("ConstPlugin", handler);
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489 | normalModuleFactory.hooks.parser
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490 | .for("javascript/esm")
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491 | .tap("ConstPlugin", handler);
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492 | }
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493 | );
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494 | }
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495 | }
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496 |
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497 | module.exports = ConstPlugin;
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