From 195103cec3aad94830f7f341387538d11e1dd06b Mon Sep 17 00:00:00 2001
From: Valeri Karpov <val@karpov.io>
Date: Sun, 21 Jul 2024 14:32:43 -0400
Subject: [PATCH 1/3] types: allow calling `SchemaType.cast()` without `parent`
 and `init` parameters

Fix #14718
Re: #9076
---
 test/schema.test.js       | 20 ++++++++++++++++++++
 test/types/schema.test.ts | 15 +++++++++++++++
 types/schematypes.d.ts    |  3 ++-
 3 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/test/schema.test.js b/test/schema.test.js
index 8cd58ba7b9f..3076c9df62a 100644
--- a/test/schema.test.js
+++ b/test/schema.test.js
@@ -3258,4 +3258,24 @@ describe('schema', function() {
 
     await q;
   });
+
+  it('supports casting object to subdocument (gh-14748) (gh-9076)', function() {
+    const nestedSchema = new Schema({ name: String });
+    nestedSchema.methods.getAnswer = () => 42;
+
+    const schema = new Schema({
+      arr: [nestedSchema],
+      singleNested: nestedSchema
+    });
+
+    // Cast to doc array
+    let subdoc = schema.path('arr').cast([{ name: 'foo' }])[0];
+    assert.ok(subdoc instanceof mongoose.Document);
+    assert.equal(subdoc.getAnswer(), 42);
+
+    // Cast to single nested subdoc
+    subdoc = schema.path('singleNested').cast({ name: 'bar' });
+    assert.ok(subdoc instanceof mongoose.Document);
+    assert.equal(subdoc.getAnswer(), 42);
+  });
 });
diff --git a/test/types/schema.test.ts b/test/types/schema.test.ts
index 9dab60d2022..e3771e0dd64 100644
--- a/test/types/schema.test.ts
+++ b/test/types/schema.test.ts
@@ -1,5 +1,6 @@
 import {
   DefaultSchemaOptions,
+  HydratedArraySubdocument,
   HydratedSingleSubdocument,
   Schema,
   Document,
@@ -1555,3 +1556,17 @@ function gh14696() {
   });
 
 }
+
+function gh14748() {
+  const nestedSchema = new Schema({ name: String });
+
+  const schema = new Schema({
+    arr: [nestedSchema],
+    singleNested: nestedSchema
+  });
+
+  // Cast to single nested subdoc
+  const subdoc = schema.path('singleNested')
+    .cast<HydratedArraySubdocument<{ name: string }>>({ name: 'bar' });
+  expectAssignable<{ name: string }>(subdoc);
+}
\ No newline at end of file
diff --git a/types/schematypes.d.ts b/types/schematypes.d.ts
index b7f1fc733b9..26eab700a81 100644
--- a/types/schematypes.d.ts
+++ b/types/schematypes.d.ts
@@ -220,7 +220,8 @@ declare module 'mongoose' {
     OptionsConstructor: SchemaTypeOptions<T>;
 
     /** Cast `val` to this schema type. Each class that inherits from schema type should implement this function. */
-    cast(val: any, doc: Document<any>, init: boolean, prev?: any, options?: any): any;
+    cast(val: any, doc?: Document<any>, init?: boolean, prev?: any, options?: any): any;
+    cast<ResultType>(val: any, doc?: Document<any>, init?: boolean, prev?: any, options?: any): ResultType;
 
     /** Sets a default value for this SchemaType. */
     default(val: any): any;

From 9da1804fed1102a709c820186c3946cd9acaa80b Mon Sep 17 00:00:00 2001
From: Valeri Karpov <val@karpov.io>
Date: Tue, 23 Jul 2024 12:29:00 -0400
Subject: [PATCH 2/3] Update test/types/schema.test.ts

Co-authored-by: hasezoey <hasezoey@gmail.com>
---
 test/types/schema.test.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/types/schema.test.ts b/test/types/schema.test.ts
index e3771e0dd64..b672d14e27e 100644
--- a/test/types/schema.test.ts
+++ b/test/types/schema.test.ts
@@ -1569,4 +1569,4 @@ function gh14748() {
   const subdoc = schema.path('singleNested')
     .cast<HydratedArraySubdocument<{ name: string }>>({ name: 'bar' });
   expectAssignable<{ name: string }>(subdoc);
-}
\ No newline at end of file
+}

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 3/3] 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 {