Hotfix: absolute URLs on server router (#10112)

Co-authored-by: Matt Brophy <matt@brophy.org>

Author: thomasverleye

.changeset/lovely-cheetahs-sip.md

@@ -0,0 +1,5 @@
+---
+"react-router-dom": patch
+---
+
+Fix SSR of absolute Link urls

contributors.yml

@@ -163,6 +163,7 @@
 - tanayv
 - theostavrides
 - thisiskartik
+- thomasverleye
 - ThornWu
 - timdorr
 - TkDodo

packages/react-router-dom/__tests__/data-static-router-test.tsx

@@ -1,3 +1,7 @@
+/**
+ * @jest-environment node
+ */
+
 import * as React from "react";
 import * as ReactDOMServer from "react-dom/server";
 import type { StaticHandlerContext } from "@remix-run/router";
@@ -642,6 +646,44 @@ describe("A <StaticRouterProvider>", () => {
     `);
   });
 
+  it("renders absolute links correctly", async () => {
+    let routes = [
+      {
+        path: "/",
+        element: (
+          <>
+            <Link to="/the/path">relative path</Link>
+            <Link to="http://localhost/the/path">absolute same-origin url</Link>
+            <Link to="https://remix.run">absolute different-origin url</Link>
+            <Link to="mailto:foo@baz.com">absolute mailto: url</Link>
+          </>
+        ),
+      },
+    ];
+    let { query } = createStaticHandler(routes);
+
+    let context = (await query(
+      new Request("http://localhost/", {
+        signal: new AbortController().signal,
+      })
+    )) as StaticHandlerContext;
+
+    let html = ReactDOMServer.renderToStaticMarkup(
+      <React.StrictMode>
+        <StaticRouterProvider
+          router={createStaticRouter(routes, context)}
+          context={context}
+        />
+      </React.StrictMode>
+    );
+    expect(html).toMatch(
+      '<a href="/the/path">relative path</a>' +
+        '<a href="http://localhost/the/path">absolute same-origin url</a>' +
+        '<a href="https://remix.run">absolute different-origin url</a>' +
+        '<a href="mailto:foo@baz.com">absolute mailto: url</a>'
+    );
+  });
+
   describe("boundary tracking", () => {
     it("tracks the deepest boundary during render", async () => {
       let routes = [

packages/react-router-dom/__tests__/polyfills/SubmitEvent.submitter.ts

@@ -1,7 +1,8 @@
 // Polyfill jsdom SubmitEvent.submitter, until https://github.com/jsdom/jsdom/pull/3481 is merged
 if (
-  typeof SubmitEvent === "undefined" ||
-  !SubmitEvent.prototype.hasOwnProperty("submitter")
+  typeof window !== "undefined" &&
+  (typeof SubmitEvent === "undefined" ||
+    !SubmitEvent.prototype.hasOwnProperty("submitter"))
 ) {
   const setImmediate = (fn, ...args) => global.setTimeout(fn, 0, ...args);
 

packages/react-router-dom/__tests__/setup.ts

@@ -2,7 +2,7 @@ import {
   TextEncoder as NodeTextEncoder,
   TextDecoder as NodeTextDecoder,
 } from "util";
-import { fetch, Request, Response } from "@remix-run/web-fetch";
+import { fetch, Request, Response, Headers } from "@remix-run/web-fetch";
 import { AbortController as NodeAbortController } from "abort-controller";
 
 import "./polyfills/SubmitEvent.submitter";
@@ -22,6 +22,7 @@ if (!globalThis.fetch) {
   // web-std/fetch Response does not currently implement Response.error()
   // @ts-expect-error
   globalThis.Response = Response;
+  globalThis.Headers = Headers;
 }
 
 if (!globalThis.AbortController) {

packages/react-router-dom/index.tsx

@@ -400,6 +400,8 @@ const isBrowser =
   typeof window.document !== "undefined" &&
   typeof window.document.createElement !== "undefined";
 
+const ABSOLUTE_URL_REGEX = /^(?:[a-z][a-z0-9+.-]*:|\/\/)/i;
+
 /**
  * The public API for rendering a history-aware <a>.
  */
@@ -422,21 +424,22 @@ export const Link = React.forwardRef<HTMLAnchorElement, LinkProps>(
     let absoluteHref;
     let isExternal = false;
 
-    if (
-      isBrowser &&
-      typeof to === "string" &&
-      /^(?:[a-z][a-z0-9+.-]*:|\/\/)/i.test(to)
-    ) {
+    if (typeof to === "string" && ABSOLUTE_URL_REGEX.test(to)) {
+      // Render the absolute href server- and client-side
       absoluteHref = to;
-      let currentUrl = new URL(window.location.href);
-      let targetUrl = to.startsWith("//")
-        ? new URL(currentUrl.protocol + to)
-        : new URL(to);
-      if (targetUrl.origin === currentUrl.origin) {
-        // Strip the protocol/origin for same-origin absolute URLs
-        to = targetUrl.pathname + targetUrl.search + targetUrl.hash;
-      } else {
-        isExternal = true;
+
+      // Only check for external origins client-side
+      if (isBrowser) {
+        let currentUrl = new URL(window.location.href);
+        let targetUrl = to.startsWith("//")
+          ? new URL(currentUrl.protocol + to)
+          : new URL(to);
+        if (targetUrl.origin === currentUrl.origin) {
+          // Strip the protocol/origin for same-origin absolute URLs
+          to = targetUrl.pathname + targetUrl.search + targetUrl.hash;
+        } else {
+          isExternal = true;
+        }
       }
     }