Silent fail of preprendering

🐞 Bug report

Hi guys, firstly, I wanted to say thanks for your hard work, truly appreciate that 🙌

What modules are related to this issue?

• builders, but I’m not sure
• common
• express-engine

Is this a regression?

Probably, no

Description

So, I was playing around with the prerendering feature, but faced an issue - some of my routes were empty after prerendering script was executed successfully (a pre-rendered page contained only <router-outlet></router-outlet><!----> instead of the component’s template). It seems that I was able to track it down. The issue only appears when I’m using localStorage in the component, but, I guess that could also be affected by the usage of any browser-specific API.

I believe that prerender script should either fail or show some kind of warning in case non-existent API (in the context of server) is used.

🔬 Minimal Reproduction

1. Initialize app via latest Angular CLI
2. Add universal
3. Add a new route/component. E.g.: a lazy module dashboard
4. Call localStorage.getItem in the constructor of the new component
5. Call prerender script (npm run prerender -- --routes /dashboard /)
6. See dist/unversal-test/browser/dashboard/index.html, there is content from src/app/dashboard/dashboard.component.html. And, there are no errors/warnings in the console

Here is the repository where I reproduced the issue, https://github.com/chernodub/ng-universal-reproduced-prerender-issue This is a breaking change https://github.com/chernodub/ng-universal-reproduced-prerender-issue/commit/656945bd4ad78e085f89fa30ad3d3c8e5acdc524, without it, prerender works fine

🔥 Exception or Error

No error or warning, that’s the problem. In case the application is somehow complex/advanced it may be very hard to understand, why prerender didn’t work 😦

🌍 Your Environment

• Dependencies
• MacOS Monterey 12.4

[alan-agius4]

After looking a bit into this, it appears that the router is not re-throwing the error

Basically the below is not working as intended. https://github.com/angular/angular/blob/d583f85701b0424496e263bf1cbc2c619869437e/packages/router/src/router.ts#L1398-L1402

[alan-agius4]

@atscott, I debugged this a bit more and as suspected this is indeed caused by the floating promises.

I tried to remove a number of floating promises (By patching the node_modules directly) and did indeed result in the error to bubble up correctly to the prerender worker.