[Bug]: useSearchParams not giving correct value with useBlocker (reopen)

[Fattimo]

What version of React Router are you using?

6.27.0

I was able to repro the bug. This is a stackblitz with an environment that allows you to repro. I used 6.27.0

https://stackblitz.com/edit/github-ypgwe9?file=src%2Fapp.tsx,src%2Fmain.tsx

I've attached two videos explaining the bug as well:

1. (control) Expected behavior:

Screen.Recording.2024-11-08.at.4.31.41.PM.mov

3. Search params returning a value that should be blocked, IF using the (prev) value in the setSearchParams function

Screen.Recording.2024-11-08.at.4.32.21.PM.mov

[Fattimo]

Original issue with repro steps: #12188 (comment)

[Fattimo]

Workaround: avoid prev at all costs. For the maintainers, very likely, mutating prev in any way triggers a change to the underlying data in a code path independent of relying on the path.

Leaving prev untouched and cloning it into an object will trigger the happy path and allow it to work.

// old code
routerSetSearchParams(
        (prev) => {
          // modify prev, e.g. prev.key = value


          return prev;
        },
      );

// workaround
routerSetSearchParams(
        (prev) => {
          const next = Object.fromEntries(prev.entries());
          // modify next in the same way you would modify prev
          return next;
        },
      );