bug: patchRoutesOnNavigation throws without triggering an error boundary

[dchenk]

I encountered a TypeError when my patchRoutesOnNavigation function threw an error but there were no partial matches. I tracked the error down to this code in packages/react-router/lib/router/router.ts:

        let boundaryId = findNearestBoundary(discoverResult.partialMatches)
          .route.id;

The problem is that findNearestBoundary can return undefined, but it's typed as returning AgnosticDataRouteMatch. I was able to reproduce the bug in a test (the first commit on this branch).

Notice the Cannot read properties of undefined error in the failing tests.

The reason this matters is that the error boundary does not get triggered in this case.

[changeset-bot]

⚠️ No Changeset found

Latest commit: 9a224f4

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR