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497 lines
14 KiB
497 lines
14 KiB
/* |
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MIT License http://www.opensource.org/licenses/mit-license.php |
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Author Tobias Koppers @sokra |
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*/ |
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"use strict"; |
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const CachedConstDependency = require("./dependencies/CachedConstDependency"); |
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const ConstDependency = require("./dependencies/ConstDependency"); |
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const { evaluateToString } = require("./javascript/JavascriptParserHelpers"); |
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const { parseResource } = require("./util/identifier"); |
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/** @typedef {import("estree").Expression} ExpressionNode */ |
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/** @typedef {import("estree").Super} SuperNode */ |
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/** @typedef {import("./Compiler")} Compiler */ |
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const collectDeclaration = (declarations, pattern) => { |
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const stack = [pattern]; |
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while (stack.length > 0) { |
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const node = stack.pop(); |
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switch (node.type) { |
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case "Identifier": |
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declarations.add(node.name); |
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break; |
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case "ArrayPattern": |
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for (const element of node.elements) { |
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if (element) { |
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stack.push(element); |
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} |
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} |
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break; |
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case "AssignmentPattern": |
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stack.push(node.left); |
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break; |
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case "ObjectPattern": |
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for (const property of node.properties) { |
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stack.push(property.value); |
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} |
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break; |
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case "RestElement": |
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stack.push(node.argument); |
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break; |
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} |
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} |
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}; |
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const getHoistedDeclarations = (branch, includeFunctionDeclarations) => { |
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const declarations = new Set(); |
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const stack = [branch]; |
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while (stack.length > 0) { |
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const node = stack.pop(); |
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// Some node could be `null` or `undefined`. |
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if (!node) continue; |
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switch (node.type) { |
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// Walk through control statements to look for hoisted declarations. |
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// Some branches are skipped since they do not allow declarations. |
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case "BlockStatement": |
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for (const stmt of node.body) { |
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stack.push(stmt); |
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} |
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break; |
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case "IfStatement": |
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stack.push(node.consequent); |
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stack.push(node.alternate); |
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break; |
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case "ForStatement": |
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stack.push(node.init); |
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stack.push(node.body); |
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break; |
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case "ForInStatement": |
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case "ForOfStatement": |
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stack.push(node.left); |
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stack.push(node.body); |
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break; |
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case "DoWhileStatement": |
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case "WhileStatement": |
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case "LabeledStatement": |
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stack.push(node.body); |
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break; |
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case "SwitchStatement": |
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for (const cs of node.cases) { |
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for (const consequent of cs.consequent) { |
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stack.push(consequent); |
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} |
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} |
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break; |
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case "TryStatement": |
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stack.push(node.block); |
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if (node.handler) { |
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stack.push(node.handler.body); |
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} |
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stack.push(node.finalizer); |
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break; |
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case "FunctionDeclaration": |
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if (includeFunctionDeclarations) { |
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collectDeclaration(declarations, node.id); |
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} |
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break; |
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case "VariableDeclaration": |
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if (node.kind === "var") { |
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for (const decl of node.declarations) { |
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collectDeclaration(declarations, decl.id); |
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} |
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} |
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break; |
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} |
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} |
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return Array.from(declarations); |
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}; |
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class ConstPlugin { |
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/** |
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* Apply the plugin |
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* @param {Compiler} compiler the compiler instance |
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* @returns {void} |
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*/ |
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apply(compiler) { |
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const cachedParseResource = parseResource.bindCache(compiler.root); |
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compiler.hooks.compilation.tap( |
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"ConstPlugin", |
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(compilation, { normalModuleFactory }) => { |
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compilation.dependencyTemplates.set( |
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ConstDependency, |
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new ConstDependency.Template() |
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); |
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compilation.dependencyTemplates.set( |
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CachedConstDependency, |
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new CachedConstDependency.Template() |
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); |
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const handler = parser => { |
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parser.hooks.statementIf.tap("ConstPlugin", statement => { |
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if (parser.scope.isAsmJs) return; |
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const param = parser.evaluateExpression(statement.test); |
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const bool = param.asBool(); |
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if (typeof bool === "boolean") { |
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if (!param.couldHaveSideEffects()) { |
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const dep = new ConstDependency(`${bool}`, param.range); |
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dep.loc = statement.loc; |
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parser.state.module.addPresentationalDependency(dep); |
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} else { |
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parser.walkExpression(statement.test); |
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} |
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const branchToRemove = bool |
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? statement.alternate |
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: statement.consequent; |
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if (branchToRemove) { |
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// Before removing the dead branch, the hoisted declarations |
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// must be collected. |
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// |
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// Given the following code: |
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// |
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// if (true) f() else g() |
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// if (false) { |
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// function f() {} |
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// const g = function g() {} |
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// if (someTest) { |
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// let a = 1 |
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// var x, {y, z} = obj |
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// } |
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// } else { |
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// … |
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// } |
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// |
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// the generated code is: |
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// |
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// if (true) f() else {} |
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// if (false) { |
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// var f, x, y, z; (in loose mode) |
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// var x, y, z; (in strict mode) |
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// } else { |
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// … |
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// } |
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// |
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// NOTE: When code runs in strict mode, `var` declarations |
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// are hoisted but `function` declarations don't. |
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// |
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let declarations; |
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if (parser.scope.isStrict) { |
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// If the code runs in strict mode, variable declarations |
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// using `var` must be hoisted. |
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declarations = getHoistedDeclarations(branchToRemove, false); |
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} else { |
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// Otherwise, collect all hoisted declaration. |
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declarations = getHoistedDeclarations(branchToRemove, true); |
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} |
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let replacement; |
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if (declarations.length > 0) { |
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replacement = `{ var ${declarations.join(", ")}; }`; |
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} else { |
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replacement = "{}"; |
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} |
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const dep = new ConstDependency( |
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replacement, |
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branchToRemove.range |
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); |
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dep.loc = branchToRemove.loc; |
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parser.state.module.addPresentationalDependency(dep); |
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} |
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return bool; |
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} |
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}); |
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parser.hooks.expressionConditionalOperator.tap( |
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"ConstPlugin", |
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expression => { |
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if (parser.scope.isAsmJs) return; |
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const param = parser.evaluateExpression(expression.test); |
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const bool = param.asBool(); |
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if (typeof bool === "boolean") { |
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if (!param.couldHaveSideEffects()) { |
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const dep = new ConstDependency(` ${bool}`, param.range); |
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dep.loc = expression.loc; |
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parser.state.module.addPresentationalDependency(dep); |
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} else { |
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parser.walkExpression(expression.test); |
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} |
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// Expressions do not hoist. |
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// It is safe to remove the dead branch. |
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// |
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// Given the following code: |
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// |
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// false ? someExpression() : otherExpression(); |
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// |
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// the generated code is: |
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// |
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// false ? 0 : otherExpression(); |
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// |
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const branchToRemove = bool |
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? expression.alternate |
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: expression.consequent; |
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const dep = new ConstDependency("0", branchToRemove.range); |
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dep.loc = branchToRemove.loc; |
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parser.state.module.addPresentationalDependency(dep); |
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return bool; |
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} |
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} |
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); |
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parser.hooks.expressionLogicalOperator.tap( |
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"ConstPlugin", |
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expression => { |
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if (parser.scope.isAsmJs) return; |
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if ( |
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expression.operator === "&&" || |
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expression.operator === "||" |
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) { |
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const param = parser.evaluateExpression(expression.left); |
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const bool = param.asBool(); |
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if (typeof bool === "boolean") { |
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// Expressions do not hoist. |
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// It is safe to remove the dead branch. |
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// |
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// ------------------------------------------ |
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// |
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// Given the following code: |
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// |
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// falsyExpression() && someExpression(); |
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// |
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// the generated code is: |
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// |
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// falsyExpression() && false; |
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// |
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// ------------------------------------------ |
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// |
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// Given the following code: |
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// |
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// truthyExpression() && someExpression(); |
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// |
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// the generated code is: |
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// |
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// true && someExpression(); |
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// |
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// ------------------------------------------ |
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// |
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// Given the following code: |
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// |
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// truthyExpression() || someExpression(); |
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// |
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// the generated code is: |
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// |
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// truthyExpression() || false; |
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// |
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// ------------------------------------------ |
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// |
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// Given the following code: |
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// |
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// falsyExpression() || someExpression(); |
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// |
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// the generated code is: |
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// |
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// false && someExpression(); |
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// |
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const keepRight = |
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(expression.operator === "&&" && bool) || |
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(expression.operator === "||" && !bool); |
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if ( |
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!param.couldHaveSideEffects() && |
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(param.isBoolean() || keepRight) |
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) { |
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// for case like |
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// |
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// return'development'===process.env.NODE_ENV&&'foo' |
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// |
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// we need a space before the bool to prevent result like |
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// |
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// returnfalse&&'foo' |
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// |
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const dep = new ConstDependency(` ${bool}`, param.range); |
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dep.loc = expression.loc; |
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parser.state.module.addPresentationalDependency(dep); |
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} else { |
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parser.walkExpression(expression.left); |
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} |
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if (!keepRight) { |
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const dep = new ConstDependency( |
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"0", |
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expression.right.range |
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); |
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dep.loc = expression.loc; |
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parser.state.module.addPresentationalDependency(dep); |
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} |
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return keepRight; |
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} |
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} else if (expression.operator === "??") { |
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const param = parser.evaluateExpression(expression.left); |
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const keepRight = param && param.asNullish(); |
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if (typeof keepRight === "boolean") { |
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// ------------------------------------------ |
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// |
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// Given the following code: |
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// |
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// nonNullish ?? someExpression(); |
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// |
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// the generated code is: |
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// |
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// nonNullish ?? 0; |
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// |
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// ------------------------------------------ |
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// |
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// Given the following code: |
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// |
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// nullish ?? someExpression(); |
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// |
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// the generated code is: |
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// |
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// null ?? someExpression(); |
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// |
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if (!param.couldHaveSideEffects() && keepRight) { |
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// cspell:word returnnull |
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// for case like |
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// |
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// return('development'===process.env.NODE_ENV&&null)??'foo' |
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// |
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// we need a space before the bool to prevent result like |
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// |
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// returnnull??'foo' |
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// |
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const dep = new ConstDependency(" null", param.range); |
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dep.loc = expression.loc; |
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parser.state.module.addPresentationalDependency(dep); |
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} else { |
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const dep = new ConstDependency( |
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"0", |
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expression.right.range |
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); |
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dep.loc = expression.loc; |
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parser.state.module.addPresentationalDependency(dep); |
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parser.walkExpression(expression.left); |
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} |
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return keepRight; |
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} |
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} |
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} |
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); |
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parser.hooks.optionalChaining.tap("ConstPlugin", expr => { |
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/** @type {ExpressionNode[]} */ |
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const optionalExpressionsStack = []; |
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/** @type {ExpressionNode|SuperNode} */ |
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let next = expr.expression; |
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while ( |
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next.type === "MemberExpression" || |
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next.type === "CallExpression" |
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) { |
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if (next.type === "MemberExpression") { |
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if (next.optional) { |
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// SuperNode can not be optional |
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optionalExpressionsStack.push( |
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/** @type {ExpressionNode} */ (next.object) |
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); |
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} |
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next = next.object; |
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} else { |
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if (next.optional) { |
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// SuperNode can not be optional |
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optionalExpressionsStack.push( |
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/** @type {ExpressionNode} */ (next.callee) |
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); |
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} |
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next = next.callee; |
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} |
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} |
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while (optionalExpressionsStack.length) { |
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const expression = optionalExpressionsStack.pop(); |
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const evaluated = parser.evaluateExpression(expression); |
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if (evaluated && evaluated.asNullish()) { |
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// ------------------------------------------ |
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// |
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// Given the following code: |
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// |
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// nullishMemberChain?.a.b(); |
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// |
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// the generated code is: |
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// |
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// undefined; |
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// |
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// ------------------------------------------ |
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// |
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const dep = new ConstDependency(" undefined", expr.range); |
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dep.loc = expr.loc; |
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parser.state.module.addPresentationalDependency(dep); |
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return true; |
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} |
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} |
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}); |
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parser.hooks.evaluateIdentifier |
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.for("__resourceQuery") |
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.tap("ConstPlugin", expr => { |
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if (parser.scope.isAsmJs) return; |
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if (!parser.state.module) return; |
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return evaluateToString( |
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cachedParseResource(parser.state.module.resource).query |
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)(expr); |
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}); |
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parser.hooks.expression |
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.for("__resourceQuery") |
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.tap("ConstPlugin", expr => { |
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if (parser.scope.isAsmJs) return; |
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if (!parser.state.module) return; |
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const dep = new CachedConstDependency( |
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JSON.stringify( |
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cachedParseResource(parser.state.module.resource).query |
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), |
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expr.range, |
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"__resourceQuery" |
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); |
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dep.loc = expr.loc; |
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parser.state.module.addPresentationalDependency(dep); |
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return true; |
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}); |
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parser.hooks.evaluateIdentifier |
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.for("__resourceFragment") |
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.tap("ConstPlugin", expr => { |
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if (parser.scope.isAsmJs) return; |
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if (!parser.state.module) return; |
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return evaluateToString( |
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cachedParseResource(parser.state.module.resource).fragment |
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)(expr); |
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}); |
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parser.hooks.expression |
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.for("__resourceFragment") |
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.tap("ConstPlugin", expr => { |
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if (parser.scope.isAsmJs) return; |
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if (!parser.state.module) return; |
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const dep = new CachedConstDependency( |
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JSON.stringify( |
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cachedParseResource(parser.state.module.resource).fragment |
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), |
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expr.range, |
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"__resourceFragment" |
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); |
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dep.loc = expr.loc; |
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parser.state.module.addPresentationalDependency(dep); |
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return true; |
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}); |
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}; |
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normalModuleFactory.hooks.parser |
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.for("javascript/auto") |
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.tap("ConstPlugin", handler); |
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normalModuleFactory.hooks.parser |
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.for("javascript/dynamic") |
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.tap("ConstPlugin", handler); |
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normalModuleFactory.hooks.parser |
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.for("javascript/esm") |
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.tap("ConstPlugin", handler); |
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} |
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); |
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} |
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} |
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module.exports = ConstPlugin;
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