feat(webpack): support Webpack 3 ModuleConcatenationPlugin

src/PreserveModuleNamePlugin.ts

@@ -18,13 +18,23 @@ export class PreserveModuleNamePlugin {
         roots = roots.map(x => path.resolve(x));
         const normalizers = extensions.map(x => new RegExp(x.replace(/\./g, "\\.") + "$", "i"));
 
+        // ModuleConcatenationPlugin merges modules into new ConcatenatedModule
+        let modulesBeforeConcat = modules.slice();
+        for (let i = 0; i < modulesBeforeConcat.length; i++) {
+          let m = modulesBeforeConcat[i];
+          // We don't `import ConcatenatedModule` and then `m instanceof ConcatenatedModule`
+          // because it was introduced in Webpack 3.0 and we're still compatible with 2.x at the moment.
+          if (m.constructor.name === "ConcatenatedModule")
+            modulesBeforeConcat.splice(i--, 1, ...m["modules"]);
+        }
+
         for (let module of getPreservedModules(modules)) {
           let preserve: string | true | undefined = module[preserveModuleName];
           let id = typeof preserve === "string" ? preserve : null;
 
           // No absolute request to preserve, we try to normalize the module resource
           if (!id && module.resource)
-            id = fixNodeModule(module, modules) || 
+            id = fixNodeModule(module, modulesBeforeConcat) || 
                  makeModuleRelative(roots, module.resource) ||
                  aliasRelative(alias, module.resource);