feat: support for env var for defining allowed hosts (#19325)

Author: CompuIves

docs/config/server-options.md

@@ -56,6 +56,10 @@ If a string starts with `.`, it will allow that hostname without the `.` and all
 If set to `true`, the server is allowed to respond to requests for any hosts.
 This is not recommended as it will be vulnerable to DNS rebinding attacks.
 
+::: details Configure via environment variable
+You can set the environment variable `__VITE_ADDITIONAL_SERVER_ALLOWED_HOSTS` to add an additional allowed host.
+:::
+
 ## server.port
 
 - **Type:** `number`

packages/vite/src/node/server/index.ts

@@ -1154,6 +1154,14 @@ export function resolveServerOptions(
     )
   }
 
+  if (
+    process.env.__VITE_ADDITIONAL_SERVER_ALLOWED_HOSTS &&
+    Array.isArray(server.allowedHosts)
+  ) {
+    const additionalHost = process.env.__VITE_ADDITIONAL_SERVER_ALLOWED_HOSTS
+    server.allowedHosts = [...server.allowedHosts, additionalHost]
+  }
+
   return server
 }