fix(dev): don't use "module" server conditions in Vitest

.changeset/lemon-buckets-matter.md

@@ -0,0 +1,5 @@
+---
+"@react-router/dev": patch
+---
+
+Don't use `"module"` server conditions in Vitest

contributors.yml

@@ -415,3 +415,4 @@
 - zeromask1337
 - zheng-chuang
 - zxTomw
+- remorses

packages/react-router-dev/vite/plugin.ts

@@ -3470,6 +3470,7 @@ export async function getEnvironmentOptionsResolvers(
   );
   let vite = getVite();
 
+
   function getBaseOptions({
     viteUserConfig,
   }: {
@@ -3544,6 +3545,14 @@ export async function getEnvironmentOptionsResolvers(
     // https://vite.dev/guide/migration.html#default-value-for-resolve-conditions
     let maybeDefaultServerConditions = vite.defaultServerConditions || [];
 
+
+    if (process.env.VITEST) {
+      // Vitest will fail to import packages that distribute invalid ESM if the condition "module" is added: https://github.com/remix-run/react-router/issues/13869
+      maybeDefaultServerConditions = maybeDefaultServerConditions.filter(
+        (condition) => condition !== "module"
+      );
+    }
+
     // There is no helpful export with the default external conditions (see
     // https://github.com/vitejs/vite/pull/20279 for more details). So, for now,
     // we are hardcording the default here.