usePrompt and useBlock: support for testing against path

[domdomegg]

We use react router to handle navigation. Some UIs have a tabbed view where the tab state is stored in the URL. The user might make changes on one tab, go to another tab, make some more changes and then save changes.

We don't want users to lose changes accidentally by navigating away. We explored using usePrompt for this, and while it stops them navigating away accidentally it also stops us switching tabs.

It would be useful to be able to have a callback function check whether the navigation should be blocked or not, maybe based on some state that the navigator has at the time, e.g. where it is trying to navigate to.

This seems very similar to #7926, but that issue was closed when these methods were temporarily removed from V6.

[domdomegg]

A workaround is to use useBlocker and handle the call to confirm yourself:

unstable_useBlocker(({ currentLocation, nextLocation }) => {
  // Ignore search and hash params, allowing users to navigate between tabs
  if (nextLocation.pathname === currentLocation.pathname) {
    return false;
  }

  return !confirm("Leave site? Changes that you made may not be saved.");
});