Stabilize useNavigate/useSubmit/fetcher.submit for data routers

.changeset/fetcher-basename.md

@@ -0,0 +1,13 @@
+---
+"react-router-dom": minor
+"@remix-run/router": minor
+---
+
+- Enable relative routing in the `@remix-run/router` when providing a source route ID from which the path is relative to:
+
+  - Example: `router.navigate("../path", { fromRouteId: "some-route" })`.
+  - This also applies to `router.fetch` which already receives a source route ID
+
+- Introduce a new `@remix-run/router` `future.v7_prependBasename` flag to enable `basename` prefixing to all paths coming into `router.navigate` and `router.fetch`.
+  - Previously the `basename` was prepended in the React Router layer, but now that relative routing is being handled by the router we need prepend the `basename` _after_ resolving any relative paths
+  - This also enables `basename` support in `useFetcher` as well

.changeset/stable-navigate-submit.md

@@ -0,0 +1,6 @@
+---
+"react-router": patch
+"react-router-dom": patch
+---
+
+When using a `RouterProvider`, `useNavigate`/`useSubmit`/`fetcher.submit` are now stable across location changes, since we can handle relative routing via the `@remix-run/router` instance and get rid of our dependence on `useLocation()`. When using `BrowserRouter`, these hooks remain unstable across location changes because they still rely on `useLocation()`.

package.json

@@ -105,19 +105,19 @@
   },
   "filesize": {
     "packages/router/dist/router.umd.min.js": {
-      "none": "44.1 kB"
+      "none": "45 kB"
     },
     "packages/react-router/dist/react-router.production.min.js": {
-      "none": "13.1 kB"
+      "none": "13.3 kB"
     },
     "packages/react-router/dist/umd/react-router.production.min.js": {
-      "none": "15.3 kB"
+      "none": "15.6 kB"
     },
     "packages/react-router-dom/dist/react-router-dom.production.min.js": {
-      "none": "11.6 kB"
+      "none": "11.8 kB"
     },
     "packages/react-router-dom/dist/umd/react-router-dom.production.min.js": {
-      "none": "17.5 kB"
+      "none": "17.7 kB"
     }
   }
 }

packages/react-router-dom-v5-compat/index.ts

@@ -177,6 +177,7 @@ export {
   UNSAFE_DataRouterContext,
   UNSAFE_DataRouterStateContext,
   UNSAFE_useScrollRestoration,
+  UNSAFE_useRouteId,
 } from "./react-router-dom";
 
 export type { StaticRouterProps } from "./lib/components";