Routing error in dev mode: TypeError: Cannot read property 'includes' of undefined (take two)

[JoshuaKGoldberg]

Verify canary release

• I verified that the issue exists in the latest Next.js canary release

Provide environment information

  Operating System:
      Platform: linux
      Arch: x64
      Version: #1 SMP Fri Apr 2 22:23:49 UTC 2021
    Binaries:
      Node: 18.2.0
      npm: 8.9.0
      Yarn: 1.22.19
      pnpm: 6.11.0
    Relevant packages:
      next: 12.1.7-canary.48
      react: 18.2.0
      react-dom: 18.2.0

What browser are you using? (if relevant)

Chrome, but n/a

How are you deploying your application? (if relevant)

n/a

Describe the Bug

#16874 is still impacting users. I have a repro! If the network request to /_next/static/development/_devPagesManifest.json fails for any reason, the Next.js dev application crashes with:

Uncaught (in promise) TypeError: Cannot read properties of undefined (reading 'includes')
    at resolveDynamicRoute (router.js?8684:1314:16)
    at _callee$ (router.js?8684:969:31)
    at tryCatch (runtime.js?ecd4:45:16)
    at Generator.invoke [as _invoke] (runtime.js?ecd4:274:1)
    at prototype.<computed> [as next] (runtime.js?ecd4:97:1)
    at asyncGeneratorStep (_async_to_generator.js?0e30:23:1)
    at _next (_async_to_generator.js?0e30:12:1)

Expected Behavior

Next.js should be resilient to that manifest failing to load.

I took a dive into the source code and there are some spicy TypeScript shenanigans happening 😄. And some TODOs about handling this correctly! #38046 is a draft PR showing what I'd suggest doing to resolve this issue.

1. The crash is coming from inside the framework, on if (pages.includes(fsPathname))
2. pages is a parameter of resolveRewrites
3. In calls to resolveRewrites, pages comes from this.pageLoader.getPageList()
4. getPageList doesn't properly handle the case of fetch(.../_next/static/development/_devPagesManifest.json) failing: return this.promisedDevPagesManifest! has a // TODO Remove this assertion as this could be undefined comment

Link to reproduction

https://stackblitz.com/edit/vercel-next-js-flnphe?file=pages%2Findex.tsx

(really, any Next.js app with a Link can demonstrate this issue)

To Reproduce

1. Start any Next.js app in development mode
2. Add a <Link> somewhere on the page
3. Visit localhost:3000 (or equivalent) in Chrome (or equivalent)
4. In the network tab, right click on the _devPagesManifest.json request and select Block request url
5. Refresh the page

Step 3 is the easiest way to simulate any of the reasons why that URL wouldn't be accessible that are mentioned in #16874. Apparently nginx configurations are more common culprits. Anecdotally I think I've seen this on CI runs that have flaky network layers (both GitHub Actions and CircleCI).

[github-actions]

This closed issue has been automatically locked because it had no new activity for a month. If you are running into a similar issue, please create a new issue with the steps to reproduce. Thank you.