From e6bab316d19e450d59e68a18ad9bbe272fc7f520 Mon Sep 17 00:00:00 2001
From: Valeri Karpov <val@karpov.io>
Date: Mon, 16 Nov 2020 17:45:27 -0500
Subject: [PATCH] chore(index.d.ts): exclude methods defined in interface from
 lean documents

Address some feedback from @taxilian

Re: #8108
---
 index.d.ts                       | 5 ++++-
 test/typescript/leanDocuments.ts | 7 +++++++
 test/typescript/main.test.js     | 3 ++-
 3 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/index.d.ts b/index.d.ts
index 0593c30015d..3184e817904 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -1704,7 +1704,10 @@ declare module "mongoose" {
 
   export type DocumentDefinition<T> = Omit<T, Exclude<keyof Document, '_id'>>;
 
-  export type LeanDocument<T> = Omit<T, Exclude<keyof Document, '_id'>>;
+  type FunctionPropertyNames<T> = { 
+    [K in keyof T]: T[K] extends Function ? K : never 
+  }[keyof T];
+  export type LeanDocument<T> = Omit<Omit<T, Exclude<keyof Document, '_id'>>, FunctionPropertyNames<T>>;
 
   class QueryCursor<DocType extends Document> extends stream.Readable {
     /**
diff --git a/test/typescript/leanDocuments.ts b/test/typescript/leanDocuments.ts
index 0f72217e1a9..6c6dd5b2859 100644
--- a/test/typescript/leanDocuments.ts
+++ b/test/typescript/leanDocuments.ts
@@ -5,19 +5,26 @@ const schema: Schema = new Schema({ name: { type: 'String' } });
 interface ITest extends Document {
   _id?: Types.ObjectId,
   name?: string;
+  testMethod: () => number;
 }
 
+schema.method('testMethod', () => 42);
+
 const Test = model<ITest>('Test', schema);
 
 void async function main() {
   const doc: ITest = await Test.findOne();
 
+  doc.testMethod();
+
   const pojo = doc.toObject();
   await pojo.save();
 
   const _doc = await Test.findOne().lean();
   await _doc.save();
 
+  _doc.testMethod();
+
   const hydrated = Test.hydrate(_doc);
   await hydrated.save();
 }();
\ No newline at end of file
diff --git a/test/typescript/main.test.js b/test/typescript/main.test.js
index b9bb974f77a..d78d07eefb6 100644
--- a/test/typescript/main.test.js
+++ b/test/typescript/main.test.js
@@ -125,9 +125,10 @@ describe('typescript syntax', function() {
     if (process.env.D && errors.length) {
       console.log(errors);
     }
-    assert.equal(errors.length, 2);
+    assert.equal(errors.length, 3);
     assert.ok(errors[0].messageText.includes('Property \'save\' does not exist'), errors[0].messageText);
     assert.ok(errors[1].messageText.includes('Property \'save\' does not exist'), errors[0].messageText);
+    assert.ok(errors[2].messageText.includes('Property \'testMethod\' does not exist'), errors[0].messageText);
   });
 });