rsnext/errors/failed-to-fetch-devpagesmanifest.md
Josh Goldberg 963585a4fc
fix: improve logging for _devPagesManifest.json loading failures (#38046)
## Bug

- [x] Fixes #38047
- ~[ ] Integration tests added: do you want them added for such an unusual edge case?~ [Comment below: skipping](https://github.com/vercel/next.js/pull/38046#issuecomment-1207444526)
- [x] Errors have helpful link attached, see `contributing.md`: ~I'll wait until this approach & error message are confirmed before thinking more deeply on how to explain the error~

Sending a draft PR as reference ahead of time. 🙂 

Doesn't resolve the root issue of why `_devPagesManifest.json` might fail to load. But does improve the log for when it happens. I'd suggest applying this same fix to `_devMiddlewareManifest.json` too.

<table>
<thead>
<tr>
<th></th>
<th>Before</th>
<th>After</th>
</tr>
</thead>
<tbody>
<tr>
<th>Console</th>
<td>
<pre>
<code>
Failed to fetch devPagesManifest TypeError: Failed to fetch
    at PageLoader.getPageList (page-loader.js?e87a:30:53)
    at _callee$ (router.js?8684:955:45)
    at ...
</code>
</pre>
<pre>
<code>
router.js?8684:1319 Uncaught (in promise) TypeError: Cannot \
read properties of undefined (reading 'includes')
    at resolveDynamicRoute (router.js?8684:1319:16)
    at _callee$
    at ...
</code>
</pre>
</td>
<td>
<pre>
<code>
Failed to fetch devPagesManifest: TypeError: Failed to fetch
    at PageLoader.getPageList (page-loader.js?e87a:30:53)
    at _callee$ (router.js?8684:955:45)
    at ...
</code>
</pre>
</td>
</tr>
<tr>
<th>Visual</th>
<td><img alt="Screenshot of a Next.js runtime error: TypeError: Cannot read properties of undefined (reading 'includes')" src="https://user-images.githubusercontent.com/3335181/175854728-8d5c2051-1229-4da7-8af1-fc95236befae.png" /></td>
<td><img alt="Screenshot of a Next.js runtime error: Error: Failed to fetch _devPagesManifest.json. Is something blocking that network request?" src="https://user-images.githubusercontent.com/3335181/175854774-07895846-1a1c-4bb8-bf57-fa696b8c6ba4.png" /></td>
</tr>
</tbody>
</table>
2022-08-07 19:36:03 +00:00

18 lines
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Markdown

# Failed to fetch devPagesManifest
#### Why This Error Occurred
The network request to load `_devPagesManifest.json` did not succeed.
The dev pages manifest file is used by `next/link` to retrieve the list of pages to be (pre-)loaded by Next.js.
If it fails, Next.js cannot properly navigate and link between pages.
#### Possible Ways to Fix It
- Make sure your browser developer tools, extensions, and any other network tools aren't blocking that request.
- If you're running your Next.js application through a proxy, nginx, or other network layer, make sure links like `/_next/*` are configured to be allowed.
### Useful Links
- [Original GitHub Issue Thread](https://github.com/vercel/next.js/issues/16874)
- [GitHub Issue Thread With Reproduction](https://github.com/vercel/next.js/issues/38047)