From 250b01b0aea91d6c2bb6560b2824adc4bc648683 Mon Sep 17 00:00:00 2001
From: Valeri Karpov <val@karpov.io>
Date: Sat, 16 Jul 2022 16:14:11 -0400
Subject: [PATCH] fix(types): avoid treating `| undefined` types as `any` in
 `Require_id` to better support `_id: String` with auto-typed schemas

Fix #12070
---
 test/types/models.test.ts | 19 ++++++++++++++++++-
 types/index.d.ts          |  6 ++----
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/test/types/models.test.ts b/test/types/models.test.ts
index 5d8e33bd1d2..8d022594753 100644
--- a/test/types/models.test.ts
+++ b/test/types/models.test.ts
@@ -1,5 +1,14 @@
 import { ObjectId } from 'bson';
-import { Schema, Document, Model, connection, model, Types, UpdateQuery, CallbackError } from 'mongoose';
+import {
+  Schema,
+  Document,
+  Model,
+  connection,
+  model,
+  Types,
+  UpdateQuery,
+  CallbackError
+} from 'mongoose';
 import { expectAssignable, expectError, expectType } from 'tsd';
 import { AutoTypedSchemaType, autoTypedSchema } from './schema.test';
 import { UpdateOneModel } from 'mongodb';
@@ -328,3 +337,11 @@ function gh12100() {
   Model.syncIndexes({ continueOnError: true, noResponse: true });
   Model.syncIndexes({ continueOnError: false, noResponse: true });
 }
+
+(function gh12070() {
+  const schema_with_string_id = new Schema({ _id: String, nickname: String });
+  const TestModel = model('test', schema_with_string_id);
+  const obj = new TestModel();
+
+  expectType<string>(obj._id);
+})();
diff --git a/types/index.d.ts b/types/index.d.ts
index 00252c43dd2..8b7a63bbc41 100644
--- a/types/index.d.ts
+++ b/types/index.d.ts
@@ -109,9 +109,7 @@ declare module 'mongoose' {
   }
 
   export type Require_id<T> = T extends { _id?: infer U }
-    ? U extends any
-      ? (T & { _id: Types.ObjectId })
-      : T & Required<{ _id: U }>
+    ? IfAny<U, T & { _id: Types.ObjectId }, T & Required<{ _id: U }>>
     : T & { _id: Types.ObjectId };
 
   export type RequireOnlyTypedId<T> = T extends { _id?: infer U; }
@@ -539,7 +537,7 @@ declare module 'mongoose' {
   export type SchemaDefinitionType<T> = T extends Document ? Omit<T, Exclude<keyof Document, '_id' | 'id' | '__v'>> : T;
 
   // Helpers to simplify checks
-  type IfAny<IFTYPE, THENTYPE> = 0 extends (1 & IFTYPE) ? THENTYPE : IFTYPE;
+  type IfAny<IFTYPE, THENTYPE, ELSETYPE = IFTYPE> = 0 extends (1 & IFTYPE) ? THENTYPE : ELSETYPE;
   type IfUnknown<IFTYPE, THENTYPE> = unknown extends IFTYPE ? THENTYPE : IFTYPE;
 
   // tests for these two types are located in test/types/lean.test.ts