mirror of https://github.com/webpack/webpack.git
498 lines
14 KiB
JavaScript
498 lines
14 KiB
JavaScript
/*
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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.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.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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