fix logic error in parallel route catch-all normalization

[ztanner]

What & Why

There was some code added in the catch-all route normalization that doesn't seem to make sense -- it was checking if the provided appPath depth was larger than the catch-all route depth, prior to inserting it. But it was comparing depths in an inconsistent way (.length vs .length - 1), and the catch all path was also considering the @slot and /page suffix as part of the path depth.

This means that if you had a @modal/[...catchAll] slot, it wouldn't be considered for a page like /foo/bar/baz, because /foo/bar/baz (depth: 4 with the current logic) and /@modal/[...catchAll]/page (depth: 3 with the current logic) signaled that the /foo/bar/baz route was "more specific" and shouldn't match the catch-all.

I think this was most likely added to resolve a bug where we were inserting optional catch-all ([[...catchAll]]) routes into parallel slots. However, optional catch-all routes are currently unsupported with parallel routes, so this feature didn't work properly and the partial support introduced a bug for regular catch-all routes.

How

This removes the confusing workaround and skips optional catch-all segments in this handling. Separately, we can add support for optional catch-all parallel routes, but doing so will require quite a bit more changes & also similar handling in Turbopack. Namely, if have a top-level optional catch-all, in both the Turbopack & current Webpack implementation, that top-level catch-all wouldn't be matched. And if you tried to have an optional catch-all slot, in both implementations, the app would error with:

You cannot define a route with the same specificity as a optional catch-all route ("/" and "/[[...catchAll]]")

because our route normalization logic does not treat slots specificity differently than pages.

Note: This keeps the test that was added when this logic was first introduced in #60776 to ensure that the case this was originally added for still passes.

Fixes #62948
Closes NEXT-2728

[ztanner]

• fix logic error in parallel route catch-all normalization #63879 👈
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General

	vercel/next.js canary	vercel/next.js 03-29-fix_logic_error_in_parallel_route_catch-all_normalization	Change
buildDuration	13.7s	13.9s	⚠️ +146ms
buildDurationCached	7.4s	6.2s	N/A
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Client Bundles (main, webpack)

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Edge SSR bundle Size

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page.js gzip	3.04 kB	3.04 kB	N/A
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Middleware size

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build cache

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0.pack gzip	1.58 MB	1.58 MB	N/A
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Overall change	0 B	0 B	✓

Diff details

Diff for middleware.js

Diff too large to display

Commit: c63e728

[fax1ty]

I don't know if these changes are related, but I still get the following error

[Error: Invalid segment Parallel("controls"), catch all segment must be the last segment (segments: [Dynamic("lang"), Dynamic("city"), Static("clinics"), OptionalCatchAll("args")])

Debug info:

• Execution of get_entrypoints_with_issues failed
• Execution of Project::entrypoints failed
• Execution of AppProject::routes failed
• Execution of directory_tree_to_entrypoints_internal failed
• Execution of directory_tree_to_entrypoints_internal failed
• Execution of directory_tree_to_entrypoints_internal failed
• Execution of directory_tree_to_entrypoints_internal failed
• Execution of directory_tree_to_entrypoints_internal failed
• Execution of directory_tree_to_loader_tree failed
• Invalid segment Parallel("controls"), catch all segment must be the last segment (segments: [Dynamic("lang"), Dynamic("city"), Static("clinics"), OptionalCatchAll("args")])] {
  code: 'GenericFailure'
  }

---

Project structure:

(The problem only occurs when using turbo)