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SideEffectsFlagPlugin.js
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SideEffectsFlagPlugin.js
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/*
MIT License http://www.opensource.org/licenses/mit-license.php
Author Tobias Koppers @sokra
*/
"use strict";
const mm = require("micromatch");
const HarmonyExportImportedSpecifierDependency = require("../dependencies/HarmonyExportImportedSpecifierDependency");
const HarmonyImportSideEffectDependency = require("../dependencies/HarmonyImportSideEffectDependency");
const HarmonyImportSpecifierDependency = require("../dependencies/HarmonyImportSpecifierDependency");
/** @typedef {import("../Module")} Module */
/** @typedef {import("../Dependency")} Dependency */
/**
* @typedef {Object} ExportInModule
* @property {Module} module the module
* @property {string} exportName the name of the export
*/
class SideEffectsFlagPlugin {
apply(compiler) {
compiler.hooks.normalModuleFactory.tap("SideEffectsFlagPlugin", nmf => {
nmf.hooks.module.tap("SideEffectsFlagPlugin", (module, data) => {
const resolveData = data.resourceResolveData;
if (
resolveData &&
resolveData.descriptionFileData &&
resolveData.relativePath
) {
const sideEffects = resolveData.descriptionFileData.sideEffects;
const hasSideEffects = SideEffectsFlagPlugin.moduleHasSideEffects(
resolveData.relativePath,
sideEffects
);
if (!hasSideEffects) {
module.factoryMeta.sideEffectFree = true;
}
}
return module;
});
nmf.hooks.module.tap("SideEffectsFlagPlugin", (module, data) => {
if (data.settings.sideEffects === false)
module.factoryMeta.sideEffectFree = true;
else if (data.settings.sideEffects === true)
module.factoryMeta.sideEffectFree = false;
});
});
compiler.hooks.compilation.tap("SideEffectsFlagPlugin", compilation => {
compilation.hooks.optimizeDependencies.tap(
"SideEffectsFlagPlugin",
modules => {
/** @type {Map<Module, Map<string, ExportInModule>>} */
const reexportMaps = new Map();
// Capture reexports of sideEffectFree modules
for (const module of modules) {
/** @type {Dependency[]} */
const removeDependencies = [];
for (const dep of module.dependencies) {
if (dep instanceof HarmonyImportSideEffectDependency) {
if (dep.module && dep.module.factoryMeta.sideEffectFree) {
removeDependencies.push(dep);
}
} else if (
dep instanceof HarmonyExportImportedSpecifierDependency
) {
if (module.factoryMeta.sideEffectFree) {
const mode = dep.getMode(true);
if (mode.type === "safe-reexport") {
let map = reexportMaps.get(module);
if (!map) {
reexportMaps.set(module, (map = new Map()));
}
for (const pair of mode.map) {
map.set(pair[0], {
module: mode.module,
exportName: pair[1]
});
}
}
}
}
}
}
// Flatten reexports
for (const map of reexportMaps.values()) {
for (const pair of map) {
let mapping = pair[1];
while (mapping) {
const innerMap = reexportMaps.get(mapping.module);
if (!innerMap) break;
const newMapping = innerMap.get(mapping.exportName);
if (newMapping) {
map.set(pair[0], newMapping);
}
mapping = newMapping;
}
}
}
// Update imports along the reexports from sideEffectFree modules
for (const pair of reexportMaps) {
const module = pair[0];
const map = pair[1];
for (let i = 0; i < module.reasons.length; i++) {
const reason = module.reasons[i];
const dep = reason.dependency;
if (
dep instanceof HarmonyImportSpecifierDependency &&
!dep.namespaceObjectAsContext
) {
const mapping = map.get(dep.id);
if (mapping) {
dep.redirectedModule = mapping.module;
dep.redirectedId = mapping.exportName;
module.reasons.splice(i--, 1);
mapping.module.addReason(
reason.module,
dep,
reason.explanation
? reason.explanation +
" (skipped side-effect-free modules)"
: "(skipped side-effect-free modules)"
);
}
}
}
}
}
);
});
}
static moduleHasSideEffects(moduleName, flagValue) {
switch (typeof flagValue) {
case "undefined":
return true;
case "boolean":
return flagValue;
case "string":
if (process.platform === "win32") {
flagValue = flagValue.replace(/\\/g, "/");
}
return mm.isMatch(moduleName, flagValue, {
matchBase: true
});
case "object":
return flagValue.some(glob =>
SideEffectsFlagPlugin.moduleHasSideEffects(moduleName, glob)
);
}
}
}
module.exports = SideEffectsFlagPlugin;