FlagDependencyUsagePlugin.js
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/*
MIT License http://www.opensource.org/licenses/mit-license.php
Author Tobias Koppers @sokra
*/
"use strict";
/** @typedef {import("./Module")} Module */
/** @typedef {import("./DependenciesBlock")} DependenciesBlock */
/** @typedef {false | true | string[]} UsedExports */
const addToSet = (a, b) => {
for (const item of b) {
if (!a.includes(item)) a.push(item);
}
return a;
};
const isSubset = (biggerSet, subset) => {
if (biggerSet === true) return true;
if (subset === true) return false;
return subset.every(item => biggerSet.indexOf(item) >= 0);
};
class FlagDependencyUsagePlugin {
apply(compiler) {
compiler.hooks.compilation.tap("FlagDependencyUsagePlugin", compilation => {
compilation.hooks.optimizeDependencies.tap(
"FlagDependencyUsagePlugin",
modules => {
const processModule = (module, usedExports) => {
module.used = true;
if (module.usedExports === true) return;
if (usedExports === true) {
module.usedExports = true;
} else if (Array.isArray(usedExports)) {
const old = module.usedExports ? module.usedExports.length : -1;
module.usedExports = addToSet(
module.usedExports || [],
usedExports
);
if (module.usedExports.length === old) {
return;
}
} else if (Array.isArray(module.usedExports)) {
return;
} else {
module.usedExports = false;
}
// for a module without side effects we stop tracking usage here when no export is used
// This module won't be evaluated in this case
if (module.factoryMeta.sideEffectFree) {
if (module.usedExports === false) return;
if (
Array.isArray(module.usedExports) &&
module.usedExports.length === 0
)
return;
}
queue.push([module, module, module.usedExports]);
};
const processDependenciesBlock = (module, depBlock, usedExports) => {
for (const dep of depBlock.dependencies) {
processDependency(module, dep);
}
for (const variable of depBlock.variables) {
for (const dep of variable.dependencies) {
processDependency(module, dep);
}
}
for (const block of depBlock.blocks) {
queue.push([module, block, usedExports]);
}
};
const processDependency = (module, dep) => {
const reference = compilation.getDependencyReference(module, dep);
if (!reference) return;
const referenceModule = reference.module;
const importedNames = reference.importedNames;
const oldUsed = referenceModule.used;
const oldUsedExports = referenceModule.usedExports;
if (
!oldUsed ||
(importedNames &&
(!oldUsedExports || !isSubset(oldUsedExports, importedNames)))
) {
processModule(referenceModule, importedNames);
}
};
for (const module of modules) {
if (!module.used) module.used = false;
}
/** @type {[Module, DependenciesBlock, UsedExports][]} */
const queue = [];
for (const preparedEntrypoint of compilation._preparedEntrypoints) {
if (preparedEntrypoint.module) {
processModule(preparedEntrypoint.module, true);
}
}
while (queue.length) {
const queueItem = queue.pop();
processDependenciesBlock(queueItem[0], queueItem[1], queueItem[2]);
}
}
);
});
}
}
module.exports = FlagDependencyUsagePlugin;