Don't swallow errors during prerender build

[olzraiti]

Command

build

Description

We migrated to newer Angular version (@angular/cli@21.0.4), and we got a lot of build errors with prerender: true.

The errors at least for route prerendering are currently very hard to pinpoint, because the error can happen in any component/module/etc that the route uses and there's no error stack.

The errors look like this:

✘ [ERROR] An error occurred while prerendering route '/en/trait-db/browse'.

Cannot read properties of undefined (reading 'trait-search-ignore')

The errors are generated here:

https://github.com/angular/angular-cli/blob/main/packages/angular/build/src/utils/server-rendering/prerender.ts#L263

This line swallows the error stack, because there's an error message almost always present and the newly created error doesn't include the original stack.

I tried adding console.log(error) above that line, and then I could see the error stack.

Error stacks are crucial. Could error management improved during building?

Describe the solution you'd like

Log error stack during build with prerender

Describe alternatives you've considered

No response

[maruthang]

Hi, I'd like to work on this issue.

Root cause: In prerender.ts, the error-handling catch blocks use err.message ?? err.stack ?? err. Since err.message is almost always defined on JavaScript Error objects, err.stack is never reached — even though err.stack contains both the message and the full stack trace.

Proposed fix: Reorder the nullish coalescing chain to err.stack ?? err.message ?? err at the three error-handling locations (lines ~120, ~269, ~374). Also add assertIsError(err) for type safety and include err.code consistently, matching the pattern already used at line 370.

This is a minimal change — just reordering existing properties. Happy to submit a PR if this approach sounds good.