From 351b28957871cb371da10204b0986efa2f49d915 Mon Sep 17 00:00:00 2001
From: Valeri Karpov <val@karpov.io>
Date: Tue, 23 Jul 2024 12:37:55 -0400
Subject: [PATCH] types: improve return value for Types.Subdocument.cast()

---
 test/types/schema.test.ts | 7 ++++++-
 types/schematypes.d.ts    | 4 +++-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/test/types/schema.test.ts b/test/types/schema.test.ts
index b672d14e27e..a9679c082b8 100644
--- a/test/types/schema.test.ts
+++ b/test/types/schema.test.ts
@@ -1565,8 +1565,13 @@ function gh14748() {
     singleNested: nestedSchema
   });
 
-  // Cast to single nested subdoc
   const subdoc = schema.path('singleNested')
     .cast<HydratedArraySubdocument<{ name: string }>>({ name: 'bar' });
   expectAssignable<{ name: string }>(subdoc);
+
+  const subdoc2 = schema.path('singleNested').cast({ name: 'bar' });
+  expectAssignable<{ name: string }>(subdoc2);
+
+  const subdoc3 = schema.path<Schema.Types.Subdocument<{ name: string }>>('singleNested').cast({ name: 'bar' });
+  expectAssignable<{ name: string }>(subdoc3);
 }
diff --git a/types/schematypes.d.ts b/types/schematypes.d.ts
index 26eab700a81..e8a0ecffdf0 100644
--- a/types/schematypes.d.ts
+++ b/types/schematypes.d.ts
@@ -444,7 +444,7 @@ declare module 'mongoose' {
         defaultOptions: Record<string, any>;
       }
 
-      class Subdocument extends SchemaType implements AcceptsDiscriminator {
+      class Subdocument<DocType = unknown> extends SchemaType implements AcceptsDiscriminator {
         /** This schema type's name, to defend against minifiers that mangle function names. */
         static schemaName: string;
 
@@ -456,6 +456,8 @@ declare module 'mongoose' {
 
         discriminator<T, U>(name: string | number, schema: Schema<T, U>, value?: string): U;
         discriminator<D>(name: string | number, schema: Schema, value?: string): Model<D>;
+
+        cast(val: any, doc?: Document<any>, init?: boolean, prev?: any, options?: any): HydratedSingleSubdocument<DocType>;
       }
 
       class String extends SchemaType {