重现方式：
npm install and then yarn dev:ssr
错误消息：
Compiled successfully.
** Anqular Universal Live Development Server is Listening on http://localhost:4201,open your browser on http://localhost:4201 **
ERROR Error: Uncaught (in promise): Error: RouterModule.forRoot() called twice. Lazy Loaded modules should use RouterModule.forChild() instead.
Error: RouterModule.forRoot() called twice. Lazy Loaded modules should use RouterModule.forChild() instead
at Object.provideForRootGuard [as useFactory] (C:Codesony20210526distspartcusstore-servermain. js:115752:15)
at Object. factory (C:Codesony20210526distspartacusstore-servermain.js:64140:28)
at R3Injector.hydrate (C:Codesony20210526distspartacusstore-servermain.js:64007:63)
at R3Injector.get (C:Codesony20210526distspartacusstore-servermain.js:63757:33)
at injectInjectorOnly (C:Codesony20210526distspartacusstore-servermain.js:49630:33)
at Module. Dinject (C:Codesony20210526distspartacusstore-servermain.js:49640:57)
SAP Spartacus 版本号： 2.1.7
分析
出问题的 homeModule：
HomeModule is importing B2cStorefrontModule, which shouldn't be imported twice in any scenario, especially shouldn't be lazy-loaded.
B2bStorefrontModule 不应该被加载两次，也不应该以懒加载的方式被加载。
但事实上，该 module 被重复加载了多次：
Any lazy-loaded module should only import the most necessary modules to avoid additional performance impact, and it's especially important for recipe modules like B2cStorefrontModule (the complete b2c storefront recipe).
Custom Module 里如果想提供配置，建议使用如下方式:
ConfigModule.withConfig()orprovideConfigutility/#page-title).
如果用户有大量的自定义逻辑，不推荐使用形如 B2cStorefrontModule 的 recipe module, 而是 building individually tailored storefronts by importing only modules that are needed.
并且，b2cStorefrontModule 在 3.x 版本被设置为 deprecated 状态，并且将来会被移除, in favor of a standardized reference structure.
更多Jerry的原创文章，尽在："汪子熙":
