fix(next-dev): don't let an app dir without real routes override pages/404#95713
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thsid wants to merge 2 commits into
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fix(next-dev): don't let an app dir without real routes override pages/404#95713thsid wants to merge 2 commits into
thsid wants to merge 2 commits into
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An `app` directory that exists but has no real app routes (e.g. only a root layout) incorrectly hijacked 404 handling away from a custom `pages/404`, because dev-mode page resolution unconditionally fell back to the built-in not-found component whenever the `app` directory existed, regardless of whether it had any real routes. Fixes vercel#58945
![vercel[bot]](https://avatars.githubusercontent.com/in/8329?s=60&v=4){kind=small}
findPagePathData fell back to a full recursive walk of the app directory (via collectAppFiles) to check whether it had any real routes, on every 404 request without a custom not-found file. Since ensurePage only dedupes concurrent calls, this ran on every distinct 404, not just once. Add a stopAfterFirstMatch option to recursiveReadDir and a hasAppRoutes helper that stops as soon as a single route is found, so a normal app (with a root layout) resolves after reading just the top-level directory instead of walking the whole tree.
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What?
Fixes a bug where the mere presence of an
appdirectory — even one with no real routes in it — would overridepages/404, instead of falling back to it as expected.Why?
The 404 page resolution logic treated the existence of the
appdirectory itself as a signal that an app-dir 404 should take precedence, rather than checking whether the app dir actually defines any routes. This causedpages/404to be silently shadowed in projects that have an (effectively empty)appdirectory alongside apagesdirectory.How?
next devcorrectly falls back topages/404when theappdirectory contains no real routes. Covers both the webpack and Turbopack dev paths.next buildwith webpack was already handled correctly by a prior fix and required no change here.test/e2e/app-dir/pages-404-with-empty-app-dir.Known remaining issue
next build --turbopack(production build) is not fixed by this PR — the root cause there is on the Rust side, in how Turbopack enumerates entrypoints, which is out of scope for this change. This case is covered by a test marked withit.failingto track it explicitly rather than leave it silently broken.Fixes #58945