From ae0661946a84ff5f379e4271c2f6613f24e97a11 Mon Sep 17 00:00:00 2001
From: Poorshad <p.shaddel@gmail.com>
Date: Tue, 5 Sep 2023 00:37:06 +0200
Subject: [PATCH 1/3] types(schematypes): use DocType for method this

---
 test/types/schema.test.ts | 31 +++++++++++++++++++++++++++++++
 types/index.d.ts          |  2 +-
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/test/types/schema.test.ts b/test/types/schema.test.ts
index 45dd2653c31..eb38016bef1 100644
--- a/test/types/schema.test.ts
+++ b/test/types/schema.test.ts
@@ -1183,3 +1183,34 @@ function gh13780() {
   type InferredType = InferSchemaType<typeof schema>;
   expectType<bigint | undefined>(null as unknown as InferredType['num']);
 }
+
+function gh13800() {
+  interface IUser {
+    firstName: string;
+    lastName: string;
+    someOtherField: string;
+  }
+  interface IUserMethods {
+    fullName(): string;
+  }
+  type UserModel = Model<IUser, {}, IUserMethods>;
+
+  // Typed Schema
+  const schema = new Schema<IUser, UserModel, IUserMethods>({
+    firstName: { type: String, required: true },
+    lastName: { type: String, required: true }
+  });
+  schema.method('fullName', function fullName() {
+     type This = typeof this;
+     expectType<IUser>(this);
+  });
+
+  // Auto Typed Schema
+  const autoTypedSchema = new Schema({
+    firstName: { type: String, required: true },
+    lastName: { type: String, required: true }
+  });
+  autoTypedSchema.method('fullName', function fullName() {
+    expectType<Omit<IUser, 'someOtherField'>>(this);
+  });
+}
\ No newline at end of file
diff --git a/types/index.d.ts b/types/index.d.ts
index 95653baf5a4..fe36ffa2217 100644
--- a/types/index.d.ts
+++ b/types/index.d.ts
@@ -293,7 +293,7 @@ declare module 'mongoose' {
     loadClass(model: Function, onlyVirtuals?: boolean): this;
 
     /** Adds an instance method to documents constructed from Models compiled from this schema. */
-    method<Context = any>(name: string, fn: (this: Context, ...args: any[]) => any, opts?: any): this;
+    method<Context = DocType>(name: string, fn: (this: Context, ...args: any[]) => any, opts?: any): this;
     method(obj: Partial<TInstanceMethods>): this;
 
     /** Object of currently defined methods on this schema. */

From 62a61d696ad0fe66d69db8af57b84e0d45277300 Mon Sep 17 00:00:00 2001
From: Poorshad <p.shaddel@gmail.com>
Date: Tue, 5 Sep 2023 16:39:35 +0200
Subject: [PATCH 2/3] use THydratedDocumentType type for this in instance
 methods

---
 test/types/schema.test.ts | 3 +--
 types/index.d.ts          | 2 +-
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/test/types/schema.test.ts b/test/types/schema.test.ts
index eb38016bef1..a4e40c9e490 100644
--- a/test/types/schema.test.ts
+++ b/test/types/schema.test.ts
@@ -1201,8 +1201,7 @@ function gh13800() {
     lastName: { type: String, required: true }
   });
   schema.method('fullName', function fullName() {
-     type This = typeof this;
-     expectType<IUser>(this);
+    expectType<IUser>(this);
   });
 
   // Auto Typed Schema
diff --git a/types/index.d.ts b/types/index.d.ts
index fe36ffa2217..840a3634e16 100644
--- a/types/index.d.ts
+++ b/types/index.d.ts
@@ -293,7 +293,7 @@ declare module 'mongoose' {
     loadClass(model: Function, onlyVirtuals?: boolean): this;
 
     /** Adds an instance method to documents constructed from Models compiled from this schema. */
-    method<Context = DocType>(name: string, fn: (this: Context, ...args: any[]) => any, opts?: any): this;
+    method<Context = THydratedDocumentType>(name: string, fn: (this: Context, ...args: any[]) => any, opts?: any): this;
     method(obj: Partial<TInstanceMethods>): this;
 
     /** Object of currently defined methods on this schema. */

From 8debef7c73c5c6f452f1c5e36d22e5a6afb0f41a Mon Sep 17 00:00:00 2001
From: Poorshad <p.shaddel@gmail.com>
Date: Tue, 5 Sep 2023 19:33:46 +0200
Subject: [PATCH 3/3] check types of fields individually in the test

---
 test/types/schema.test.ts | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/test/types/schema.test.ts b/test/types/schema.test.ts
index a4e40c9e490..b6726bfdc78 100644
--- a/test/types/schema.test.ts
+++ b/test/types/schema.test.ts
@@ -1201,7 +1201,10 @@ function gh13800() {
     lastName: { type: String, required: true }
   });
   schema.method('fullName', function fullName() {
-    expectType<IUser>(this);
+    expectType<string>(this.firstName);
+    expectType<string>(this.lastName);
+    expectType<string>(this.someOtherField);
+    expectType<IUserMethods['fullName']>(this.fullName);
   });
 
   // Auto Typed Schema
@@ -1210,6 +1213,8 @@ function gh13800() {
     lastName: { type: String, required: true }
   });
   autoTypedSchema.method('fullName', function fullName() {
-    expectType<Omit<IUser, 'someOtherField'>>(this);
+    expectType<string>(this.firstName);
+    expectType<string>(this.lastName);
+    expectError<string>(this.someOtherField);
   });
 }
\ No newline at end of file