fix(router-generator): do not allow "_" as a routeFileIgnorePrefix (#…

…2339)

* fix(router-generator): do not allow "_" as a `routeFIleIgnorePrefix`

* fix(router-generator): prompt the user if the rootRoute is undefined

packages/router-generator/src/config.ts

@@ -119,5 +119,15 @@ ERROR: The "experimental.enableCodeSplitting" flag has been made stable and is n
       `The "indexToken" and "routeToken" options must be different.`,
     )
   }
+
+  if (
+    config.routeFileIgnorePrefix &&
+    config.routeFileIgnorePrefix.trim() === '_'
+  ) {
+    throw new Error(
+      `The "routeFileIgnorePrefix" cannot be an underscore ("_"). This is a reserved character used to denote a pathless route. Please use a different prefix.`,
+    )
+  }
+
   return config
 }

packages/router-generator/src/generator.ts

@@ -80,8 +80,13 @@ export async function generator(config: Config) {
 
   const { rootRouteNode, routeNodes: beforeRouteNodes } = getRouteNodesResult
   if (rootRouteNode === undefined) {
-    throw new Error(`rootRouteNode must not be undefined`)
+    let errorMessage = `rootRouteNode must not be undefined. Make sure you've added your root route into the route-tree.`
+    if (!config.virtualRouteConfig) {
+      errorMessage += `\nMake sure that you add a "${rootPathId}.${config.disableTypes ? 'js' : 'tsx'}" file to your routes directory.\nAdd the file in: "${config.routesDirectory}/${rootPathId}.${config.disableTypes ? 'js' : 'tsx'}"`
+    }
+    throw new Error(errorMessage)
   }
+
   const preRouteNodes = multiSortBy(beforeRouteNodes, [
     (d) => (d.routePath === '/' ? -1 : 1),
     (d) => d.routePath?.split('/').length,