### What?
Fixes#61611
### Why?
Any one having custom server may be having logic to set cookies during
GET requests too. Currently nextjs in app directory does not allow to do
so but with custom server its very much possible.
### How?
By merging cookies of redirect response and server action POSt response
### Tests
I have added one more test to existing suite and it passing with fix in
place.
### Notes
This bug is reproducible only if developer has custom server on top of
next app but still very probable
---------
Co-authored-by: Shu Ding <g@shud.in>
Co-authored-by: JJ Kasper <jj@jjsweb.site>
### What?
Fixes#58570
### How?
Include the **basePath** to the **fetchUrl** to ensure the relative URL
matches the app when deployed under a **basePath**.
### Tested?
I have added an **e2e** test with a basic custom server & server action
redirect.
This test was confirmed to **catch** the bug when running it without the
fix in place. When running it you will get the failed result.
```
FAIL test/e2e/app-dir/app-basepath-custom-server/index.test.ts (12.293 s)
custom-app-render
✕ redirects properly when server action handler uses `redirect` (1661 ms)
● custom-app-render › redirects properly when server action handler uses `redirect`
expect(received).not.toEqual(expected) // deep equality
Expected: not ["/base/another", 200]
45 | // if broken, this will include a 200 from the /base/another indicating a full page redirect
46 | responses.forEach((res) => {
> 47 | expect(res).not.toEqual(['/base/another', 200])
| ^
48 | })
49 | })
50 | }
at toEqual (e2e/app-dir/app-basepath-custom-server/index.test.ts:47:25)
at Array.forEach (<anonymous>)
at Object.forEach (e2e/app-dir/app-basepath-custom-server/index.test.ts:46:17)
Test Suites: 1 failed, 1 total
Tests: 1 failed, 1 total
Snapshots: 0 total
Time: 12.321 s, estimated 22 s
Ran all test suites matching /test\/e2e\/app-dir\/app-basepath-custom-server/i.
ELIFECYCLE Command failed with exit code 1.
ELIFECYCLE Command failed with exit code 1.
ELIFECYCLE Command failed with exit code 1.
```
### Notes
Not sure if there are any edge cases where the `fetchUrl` is now broken
in other use cases where there is no **basePath**, I assume the string
would be empty `""` and result in the same URL as before, but not sure?
### Disclosure
~I am not that familiar with the Next.js code base and this is my first
PR. I was struggling to find out how to grab the **basePath** from
`next.config.js`, but then noticed the **assetPrefix** inside the
function matched, so decided to use that for minimal change. I don't
know if there are any caveats with this approach, but could consider
switching to pull directly from the config file, if that's possible?~
**Update:** Figured out where the **basePath** came from and switched
it.
---------
Co-authored-by: Colton Ehrman <cehrman@paypal.com>
Co-authored-by: Tim Neutkens <tim@timneutkens.nl>
