rsnext/packages/next
Willi#m ⬣ 78c9793a53
fix useSelectedLayoutSegment's support for parallel routes (#60912)
fixes NEXT-2173
Fixes #59968

### TODOs

- [x] recreate [repro](https://github.com/williamli/nextjs-NEXT-2173) 
- [x] patch `useSelectedLayoutSegment` to support parallel routes (see
"What")
- [x] check `useSelectedLayoutSegments` to see if it is affected
- [x] add test cases
- [x] finalise PR description

### What?

`useSelectedLayoutSegment` does not return the name of the active state
of parallel route slots.

#### Expected Behaviour

According to
https://nextjs.org/docs/app/building-your-application/routing/parallel-routes#useselectedlayoutsegments

> When a user navigates to app/@auth/login (or /login in the URL bar),
loginSegments will be equal to the string "login".

👉🏽 We should update the docs to explain `null` and __DEFAULT__ result as
well.

According to the [API reference for
useSelectedLayoutSegment](https://nextjs.org/docs/app/api-reference/functions/use-selected-layout-segment#returns):

> useSelectedLayoutSegment returns a string of the active segment or
null if one doesn't exist.

> For example, given the Layouts and URLs below, the returned segment
would be:

> <img width="881" alt="CleanShot 2024-01-20 at 14 50 52@2x"
src="https://github.com/vercel/next.js/assets/179761/bfaa34c8-3139-4ec3-bd70-4346c682e36b">


#### Current Behaviour

Currently a string "children" is returned for everything inside a
parallel route with active state and `__DEFAULT__` is returned if there
is no active state for the parallel route (since the `default.tsx` is
loaded). ~`null` is returned when the `default.tsx` is not loaded
(possibly caused by another bug, see test case 5).~

#### Reproduction

[GitHub Repo](https://github.com/williamli/nextjs-NEXT-2173) is created
based on the example provided in [Next.js docs for using
`useSelectedLayoutSegment` with Parallel
Routes](https://nextjs.org/docs/app/building-your-application/routing/parallel-routes#useselectedlayoutsegments).

#### Test Cases

1. If you visit https://next-2173.vercel.app/, you get loginSegments:
__DEFAULT__ (hard navigation) or children (soft navigation after
returning from a visit to /login)
2. If you soft nav to (/app/@auth/login and /app/@nav/login)
https://next-2173.vercel.app/login, you get
    1. loginSegment: `children` (expected value should be `login`)
    2. navSegment: `children` (expected value should be `login`)
3. If you soft nav to (/app/@auth/reset)
https://next-2173.vercel.app/reset, you get
    1. loginSegments: `children` (expected value should be `reset`)
    2. navSegment: `children` (expected value should be `login`)
4. If you soft nav to (/app/@auth/reset/withEmail)
https://next-2173.vercel.app/reset/withEmail, you get
    1. loginSegments: `children` (expected value should be `withEmail`)
    2. navSegment: `children` (expected value should be `login`)
5. ~If you hard nav to (/app/@auth/reset/withEmail)
https://next-2173.vercel.app/reset/withEmail, you get an unexpected
result due to possibly another bug:~
* ~navSegment is `null` on the deployed (Vercel) version, the navSlot is
*not* loaded~
* ~navSegment is `__DEFAULT__` on local dev, the navSlot loads
`/app/@nav/default.tsx`.~


### Why?

In `packages/next/src/client/components/navigation.ts`,
`getSelectedLayoutSegmentPath` is called and returns the correct
segmentPath for parallel routes (even though there is a TODO comment
indicating this function needs to be updated to handle parallel routes)
but `useSelectedLayoutSegment` failed to return the correct segment when
a parallelRouteKey is provided.

### How?

`useSelectedLayoutSegment` is updated to return
selectedLayoutSegments[0] for non parallel routes (original logic), but
it will return the last segments for parallel routes (or null if nothing
is active).

```
return parallelRouteKey === 'children'
    ? selectedLayoutSegments[0]
    : selectedLayoutSegments[selectedLayoutSegments.length-1] ?? null
```

---------

Co-authored-by: Zack Tanner <zacktanner@gmail.com>
2024-01-23 15:53:45 -08:00
..
compat
experimental/testmode
font
image-types
legacy
navigation-types/compat Update useParams typing to assume a given shape (#55126) 2023-09-14 20:20:42 +00:00
src fix useSelectedLayoutSegment's support for parallel routes (#60912) 2024-01-23 15:53:45 -08:00
types Use precompiled source-map in overlay middleware (#60932) 2024-01-22 10:04:34 +01:00
amp.d.ts
amp.js
app.d.ts
app.js
babel.d.ts
babel.js
cache.d.ts cache: add unstable_noStore API (#56930) 2023-10-17 14:52:46 +00:00
cache.js chore: fix a typo (#57272) 2023-10-23 17:10:35 +00:00
client.d.ts
client.js
config.d.ts server: bundle vendored react (#55362) 2023-09-15 19:49:39 +00:00
config.js server: bundle vendored react (#55362) 2023-09-15 19:49:39 +00:00
constants.d.ts
constants.js
document.d.ts
document.js
dynamic.d.ts
dynamic.js
error.d.ts
error.js
head.d.ts
head.js
headers.d.ts
headers.js
image.d.ts
image.js
index.d.ts fix(ts): auto-complete next/headers (#60817) 2024-01-18 15:01:22 +01:00
jest.d.ts
jest.js
license.md chore: update Copyright time from 2023 to 2024 (#60071) 2024-01-02 11:06:02 -08:00
link.d.ts
link.js
navigation.d.ts
navigation.js
og.d.ts Move ImageResponse to next/og (#56662) 2023-10-19 14:26:48 +00:00
og.js Move ImageResponse to next/og (#56662) 2023-10-19 14:26:48 +00:00
package.json v14.1.1-canary.8 2024-01-23 23:23:10 +00:00
README.md
router.d.ts
router.js
script.d.ts
script.js
server.d.ts
server.js
taskfile-ncc.js Use precompiled source-map in overlay middleware (#60932) 2024-01-22 10:04:34 +01:00
taskfile-swc.js Use new JSX transform (#56294) 2023-12-09 00:17:50 +01:00
taskfile-watch.js
taskfile-webpack.js avoid output of webpack stats (#61023) 2024-01-23 11:53:19 +01:00
taskfile.js Use more precompiled deps in react-dev-overlay (#60959) 2024-01-22 13:53:42 +01:00
tsconfig.json Use new JSX transform (#56294) 2023-12-09 00:17:50 +01:00
web-vitals.d.ts
web-vitals.js
webpack.config.js Optionally bundle legacy react-dom/server APIs based on usage (#59737) 2023-12-20 16:50:06 +01:00

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