do not typegen params for layout routes with a corresponding index (#13131)

* do not typegen params for layout routes with a corresponding index

* changeset

---------

Co-authored-by: Pedro Cattori <[email protected]>

Author: robbtraister

.changeset/yellow-glasses-sort.md

@@ -0,0 +1,5 @@
+---
+"@react-router/dev": patch
+---
+
+Fix duplicated entries in typegen for layout routes and their corresponding index route

packages/react-router-dev/typegen/index.ts

@@ -103,6 +103,12 @@ function register(ctx: Context) {
 
   const { t } = Babel;
 
+  const indexPaths = new Set(
+    Object.values(ctx.config.routes)
+      .filter((route) => route.index)
+      .map((route) => route.path)
+  );
+
   const typeParams = t.tsTypeAliasDeclaration(
     t.identifier("Params"),
     null,
@@ -112,6 +118,9 @@ function register(ctx: Context) {
           // filter out pathless (layout) routes
           if (route.id !== "root" && !route.path) return undefined;
 
+          // filter out layout routes that have a corresponding index
+          if (!route.index && indexPaths.has(route.path)) return undefined;
+
           const lineage = Route.lineage(ctx.config.routes, route);
           const fullpath = Route.fullpath(lineage);
           const params = Params.parse(fullpath);