Vite: Enable HMR for .md and .mdx files

.changeset/wet-bulldogs-appear.md

@@ -0,0 +1,5 @@
+---
+"@remix-run/dev": patch
+---
+
+Vite: Enable HMR for .md and .mdx files

integration/vite-hmr-hdr-test.ts

@@ -57,6 +57,61 @@ test("Vite / HMR & HDR / express", async ({ page, browserName, customDev }) => {
   await workflow({ page, browserName, cwd, port });
 });
 
+test("Vite / HMR & HDR / mdx", async ({ page, viteDev }) => {
+  let files: Files = async ({ port }) => ({
+    "vite.config.ts": `
+      import { defineConfig } from "vite";
+      import { unstable_vitePlugin as remix } from "@remix-run/dev";
+      import mdx from "@mdx-js/rollup";
+
+      export default defineConfig({
+        ${await viteConfig.server({ port })}
+        plugins: [
+          mdx(),
+          remix(),
+        ],
+      });
+    `,
+    "app/component.tsx": `
+      import {useState} from "react";
+
+      export const Counter = () => {
+        const [count, setCount] = useState(0);
+        return <button onClick={() => setCount(count => count + 1)}>Count: {count}</button>
+      }
+    `,
+    "app/routes/mdx.mdx": `
+      import { Counter } from "../component";
+
+      # MDX Title (HMR: 0)
+
+      <Counter />
+    `,
+  });
+
+  let { port, cwd } = await viteDev(files);
+  let edit = createEditor(cwd);
+  await page.goto(`http://localhost:${port}/mdx`, {
+    waitUntil: "networkidle",
+  });
+
+  await expect(page.locator("h1")).toHaveText("MDX Title (HMR: 0)");
+  let button = page.locator("button");
+  await expect(button).toHaveText("Count: 0");
+  await button.click();
+  await expect(button).toHaveText("Count: 1");
+
+  await edit("app/routes/mdx.mdx", (contents) =>
+    contents.replace("(HMR: 0)", "(HMR: 1)")
+  );
+  await page.waitForLoadState("networkidle");
+
+  await expect(page.locator("h1")).toHaveText("MDX Title (HMR: 1)");
+  await expect(page.locator("button")).toHaveText("Count: 1");
+
+  expect(page.errors).toEqual([]);
+});
+
 async function workflow({
   page,
   browserName,

packages/remix-dev/vite/plugin.ts

@@ -1491,7 +1491,8 @@ export const remixVitePlugin: RemixVitePlugin = (remixUserConfig = {}) => {
         if (id.includes("/node_modules/")) return;
 
         let [filepath] = id.split("?");
-        if (!/.[tj]sx?$/.test(filepath)) return;
+        let extensionsRE = /\.(jsx?|tsx?|mdx?)$/;
+        if (!extensionsRE.test(filepath)) return;
 
         let devRuntime = "react/jsx-dev-runtime";
         let ssr = options?.ssr === true;