From 6c7833432bd71a429a6417b065639ebbdb3edcab Mon Sep 17 00:00:00 2001
From: Valeri Karpov <val@karpov.io>
Date: Sun, 6 Nov 2022 20:20:13 -0500
Subject: [PATCH 1/2] fix(types): set `this` to doc type in
 `SchemaType.prototype.validate()`

Fix #12590
---
 test/types/schema.test.ts | 18 ++++++++++++++++++
 types/index.d.ts          |  2 +-
 types/schematypes.d.ts    | 10 +++++++---
 3 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/test/types/schema.test.ts b/test/types/schema.test.ts
index b0e148afce5..c818bedaf93 100644
--- a/test/types/schema.test.ts
+++ b/test/types/schema.test.ts
@@ -897,3 +897,21 @@ function gh12562() {
     }
   );
 }
+
+function gh12590() {
+  const UserSchema = new Schema({
+    _password: String
+  });
+
+  type User = InferSchemaType<typeof UserSchema>;
+
+  expectType<SchemaType<User>>(UserSchema.path('hashed_password'));
+
+  UserSchema.path('hashed_password').validate(function(v: any) {
+    expectType<HydratedDocument<User>>(this);
+    if (this._password && this._password.length < 8) {
+      this.invalidate('password', 'Password must be at least 8 characters.');
+    }
+  });
+
+}
diff --git a/types/index.d.ts b/types/index.d.ts
index 97663a46d84..4f7cc0e1393 100644
--- a/types/index.d.ts
+++ b/types/index.d.ts
@@ -258,8 +258,8 @@ declare module 'mongoose' {
     obj: SchemaDefinition<SchemaDefinitionType<EnforcedDocType>>;
 
     /** Gets/sets schema paths. */
+    path<ResultType extends SchemaType = SchemaType<any, HydratedDocument<DocType, TInstanceMethods>>>(path: string): ResultType;
     path<pathGeneric extends keyof EnforcedDocType>(path: pathGeneric): SchemaType<EnforcedDocType[pathGeneric]>;
-    path<ResultType extends SchemaType = SchemaType>(path: string): ResultType;
     path(path: string, constructor: any): this;
 
     /** Lists all paths and their type in the schema. */
diff --git a/types/schematypes.d.ts b/types/schematypes.d.ts
index 093651d1408..513037cffe5 100644
--- a/types/schematypes.d.ts
+++ b/types/schematypes.d.ts
@@ -188,7 +188,11 @@ declare module 'mongoose' {
     [other: string]: any;
   }
 
-  class SchemaType<T = any> {
+  interface Validator {
+    message?: string; type?: string; validator?: Function
+  }
+
+  class SchemaType<T = any, DocType = any> {
     /** SchemaType constructor */
     constructor(path: string, options?: AnyObject, instance?: string);
 
@@ -270,10 +274,10 @@ declare module 'mongoose' {
     unique(bool: boolean): this;
 
     /** The validators that Mongoose should run to validate properties at this SchemaType's path. */
-    validators: { message?: string; type?: string; validator?: Function }[];
+    validators: Validator[];
 
     /** Adds validator(s) for this document path. */
-    validate(obj: RegExp | Function | any, errorMsg?: string, type?: string): this;
+    validate(obj: RegExp | ((this: DocType, value: any, validatorProperties?: Validator) => any), errorMsg?: string, type?: string): this;
   }
 
   namespace Schema {

From 78b91b4c36d5f8757421dc8def589b16ae4ff628 Mon Sep 17 00:00:00 2001
From: Valeri Karpov <val@karpov.io>
Date: Mon, 7 Nov 2022 12:02:53 -0500
Subject: [PATCH 2/2] test(types): address code review comments

---
 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 c818bedaf93..6bf7bcd94d2 100644
--- a/test/types/schema.test.ts
+++ b/test/types/schema.test.ts
@@ -907,7 +907,7 @@ function gh12590() {
 
   expectType<SchemaType<User>>(UserSchema.path('hashed_password'));
 
-  UserSchema.path('hashed_password').validate(function(v: any) {
+  UserSchema.path('hashed_password').validate(function(v) {
     expectType<HydratedDocument<User>>(this);
     if (this._password && this._password.length < 8) {
       this.invalidate('password', 'Password must be at least 8 characters.');