From f2481e384662052e3e2316220d0b195e49e384c1 Mon Sep 17 00:00:00 2001
From: Brandon Johnson <bjohn465+github@gmail.com>
Date: Sat, 22 Feb 2025 16:08:24 -0700
Subject: [PATCH 1/4] Add failing tests for ReadonlyMap and ReadonlySet

---
 packages/react-router/lib/types/route-data.ts | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/packages/react-router/lib/types/route-data.ts b/packages/react-router/lib/types/route-data.ts
index 9dc2b6b4da..26318a444c 100644
--- a/packages/react-router/lib/types/route-data.ts
+++ b/packages/react-router/lib/types/route-data.ts
@@ -108,6 +108,25 @@ type __tests = [
     >
   >,
   Expect<Equal<ServerDataFrom<() => { a: string } | Response>, { a: string }>>,
+  Expect<
+    Equal<
+      ServerDataFrom<
+        () => {
+          map: Map<string, number>;
+          readonlyMap: ReadonlyMap<string, number>;
+        }
+      >,
+      { map: Map<string, number>; readonlyMap: ReadonlyMap<string, number> }
+    >
+  >,
+  Expect<
+    Equal<
+      ServerDataFrom<
+        () => { set: Set<string>; readonlySet: ReadonlySet<string> }
+      >,
+      { set: Set<string>; readonlySet: ReadonlySet<string> }
+    >
+  >,
 
   // ClientDataFrom
   Expect<Equal<ClientDataFrom<any>, undefined>>,

From aa9a74996cb604d62abc643f69dbd57f57fa3a48 Mon Sep 17 00:00:00 2001
From: Brandon Johnson <bjohn465+github@gmail.com>
Date: Sat, 22 Feb 2025 16:16:16 -0700
Subject: [PATCH 2/4] Add bjohn465 to contributors.yml

This is me signing the Contributor License Agreement (CLA).
---
 contributors.yml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/contributors.yml b/contributors.yml
index cfbb9400d8..5ad6440c45 100644
--- a/contributors.yml
+++ b/contributors.yml
@@ -47,6 +47,7 @@
 - BDomzalski
 - bhbs
 - bilalk711
+- bjohn465
 - bobziroll
 - bravo-kernel
 - Brendonovich

From 05e2051609af19629bd707be6f8f8a20a63696a2 Mon Sep 17 00:00:00 2001
From: Brandon Johnson <bjohn465+github@gmail.com>
Date: Sun, 23 Feb 2025 08:46:37 -0700
Subject: [PATCH 3/4] Add ReadonlyMap and ReadonlySet to Serialize type

---
 packages/react-router/lib/types/route-data.ts | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/packages/react-router/lib/types/route-data.ts b/packages/react-router/lib/types/route-data.ts
index 26318a444c..fae6eb1d5c 100644
--- a/packages/react-router/lib/types/route-data.ts
+++ b/packages/react-router/lib/types/route-data.ts
@@ -25,7 +25,9 @@ type Serialize<T> =
 
   // Map & Set
   T extends Map<infer K, infer V> ? Map<Serialize<K>, Serialize<V>> :
+  T extends ReadonlyMap<infer K, infer V> ? ReadonlyMap<Serialize<K>, Serialize<V>> :
   T extends Set<infer U> ? Set<Serialize<U>> :
+  T extends ReadonlySet<infer U> ? ReadonlySet<Serialize<U>> :
 
   // Array
   T extends [] ? [] :

From bc4c0a838433f5d208b970ce3f5c1e3ae43e89e8 Mon Sep 17 00:00:00 2001
From: Brandon Johnson <bjohn465+github@gmail.com>
Date: Sun, 23 Feb 2025 08:56:53 -0700
Subject: [PATCH 4/4] Add changeset

---
 .changeset/fresh-pugs-relax.md | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 .changeset/fresh-pugs-relax.md

diff --git a/.changeset/fresh-pugs-relax.md b/.changeset/fresh-pugs-relax.md
new file mode 100644
index 0000000000..2c98b6c1f6
--- /dev/null
+++ b/.changeset/fresh-pugs-relax.md
@@ -0,0 +1,5 @@
+---
+"react-router": patch
+---
+
+Maintain `ReadonlyMap` and `ReadonlySet` types in server response data.