1 files changed, 168 insertions, 0 deletions
diff --git a/node_modules/webpack/lib/optimize/SideEffectsFlagPlugin.js b/node_modules/webpack/lib/optimize/SideEffectsFlagPlugin.js
new file mode 100644
index 00000000..4b618c29
--- /dev/null
+++ b/node_modules/webpack/lib/optimize/SideEffectsFlagPlugin.js
@@ -0,0 +1,168 @@
+/*
+	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];
+						let newReasons = undefined;
+						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;
+									mapping.module.addReason(
+										reason.module,
+										dep,
+										reason.explanation
+											? reason.explanation +
+											  " (skipped side-effect-free modules)"
+											: "(skipped side-effect-free modules)"
+									);
+									// removing the currect reason, by not adding it to the newReasons array
+									// lazily create the newReasons array
+									if (newReasons === undefined) {
+										newReasons = i === 0 ? [] : module.reasons.slice(0, i);
+									}
+									continue;
+								}
+							}
+							if (newReasons !== undefined) newReasons.push(reason);
+						}
+						if (newReasons !== undefined) {
+							module.reasons = newReasons;
+						}
+					}
+				}
+			);
+		});
+	}
+
+	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;