feat: allow Link's "to" prop to accept external urls

packages/react-router-dom/__tests__/link-href-test.tsx

@@ -89,6 +89,45 @@ describe("<Link> href", () => {
         ["/about", "/about"]
       );
     });
+
+    test('<Link to="https://remix.run"> is treated as external link', () => {
+      let renderer: TestRenderer.ReactTestRenderer;
+      TestRenderer.act(() => {
+        renderer = TestRenderer.create(
+          <MemoryRouter initialEntries={["/inbox/messages"]}>
+            <Routes>
+              <Route path="inbox">
+                <Route
+                  path="messages"
+                  element={<Link to="https://remix.run" />}
+                />
+              </Route>
+            </Routes>
+          </MemoryRouter>
+        );
+      });
+
+      expect(renderer.root.findByType("a").props.href).toEqual(
+        "https://remix.run"
+      );
+    });
+
+    test('<Link to="//remix.run"> is treated as external link', () => {
+      let renderer: TestRenderer.ReactTestRenderer;
+      TestRenderer.act(() => {
+        renderer = TestRenderer.create(
+          <MemoryRouter initialEntries={["/inbox/messages"]}>
+            <Routes>
+              <Route path="inbox">
+                <Route path="messages" element={<Link to="//remix.run" />} />
+              </Route>
+            </Routes>
+          </MemoryRouter>
+        );
+      });
+
+      expect(renderer.root.findByType("a").props.href).toEqual("//remix.run");
+    });
   });
 
   describe("in a dynamic route", () => {

packages/react-router-dom/index.tsx

@@ -409,7 +409,9 @@ export const Link = React.forwardRef<HTMLAnchorElement, LinkProps>(
     },
     ref
   ) {
-    let href = useHref(to, { relative });
+    let toString = typeof to === "string" ? to : createPath(to);
+    let isExternal = /^(?:[a-z][a-z0-9+.-]*:|\/\/)/i.test(toString);
+    let href = useHref(toString, { relative });
     let internalOnClick = useLinkClickHandler(to, {
       replace,
       state,
@@ -430,8 +432,8 @@ export const Link = React.forwardRef<HTMLAnchorElement, LinkProps>(
       // eslint-disable-next-line jsx-a11y/anchor-has-content
       <a
         {...rest}
-        href={href}
-        onClick={reloadDocument ? onClick : handleClick}
+        href={isExternal ? toString : href}
+        onClick={isExternal || reloadDocument ? onClick : handleClick}
         ref={ref}
         target={target}
       />