From b035a33d3ee1fd3d5bf1cc9db6b7f6b786810ec7 Mon Sep 17 00:00:00 2001
From: Eugene Korshenko <korshenko.ea@gmail.com>
Date: Mon, 10 Jan 2022 23:34:51 +0200
Subject: [PATCH 1/3] types: Fixes `Query.projection` method types

---
 index.d.ts | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/index.d.ts b/index.d.ts
index a800870fcf6..523e29132af 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -2117,6 +2117,8 @@ declare module 'mongoose' {
 
   type UnpackedIntersection<T, U> = T extends (infer V)[] ? (V & U)[] : T & U;
 
+  type ProjectionFields<DocType> = {[Key in keyof Omit<LeanDocument<DocType>, '__v'>]?: number} & Record<string, number>;
+
   class Query<ResultType, DocType, THelpers = {}, RawDocType = DocType> {
     _mongooseOptions: MongooseQueryOptions;
 
@@ -2403,7 +2405,9 @@ declare module 'mongoose' {
     populate<Paths = {}>(options: PopulateOptions | Array<PopulateOptions>): QueryWithHelpers<UnpackedIntersection<ResultType, Paths>, DocType, THelpers, RawDocType>;
 
     /** Get/set the current projection (AKA fields). Pass `null` to remove the current projection. */
-    projection(fields?: any | null): this;
+    projection(): ProjectionFields<DocType> | null;
+    projection(fields: null): null;
+    projection(fields?: ProjectionFields<DocType>): ProjectionFields<DocType>;
 
     /** Determines the MongoDB nodes from which to read. */
     read(pref: string | mongodb.ReadPreferenceMode, tags?: any[]): this;

From 35286d355c86e4bef8f74b7e9355bbd663501355 Mon Sep 17 00:00:00 2001
From: Eugene Korshenko <korshenko.ea@gmail.com>
Date: Tue, 11 Jan 2022 00:32:34 +0200
Subject: [PATCH 2/3] Add tests

---
 index.d.ts                 |  2 +-
 test/typescript/queries.ts | 13 ++++++++++++-
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/index.d.ts b/index.d.ts
index 523e29132af..c84eb966175 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -2407,7 +2407,7 @@ declare module 'mongoose' {
     /** Get/set the current projection (AKA fields). Pass `null` to remove the current projection. */
     projection(): ProjectionFields<DocType> | null;
     projection(fields: null): null;
-    projection(fields?: ProjectionFields<DocType>): ProjectionFields<DocType>;
+    projection(fields?: ProjectionFields<DocType> | string): ProjectionFields<DocType>;
 
     /** Determines the MongoDB nodes from which to read. */
     read(pref: string | mongodb.ReadPreferenceMode, tags?: any[]): this;
diff --git a/test/typescript/queries.ts b/test/typescript/queries.ts
index f0dc5418e3e..baea0f4063a 100644
--- a/test/typescript/queries.ts
+++ b/test/typescript/queries.ts
@@ -116,6 +116,17 @@ query instanceof Query;
 Test.findOne().where({ name: 'test' });
 Test.where().find({ name: 'test' });
 
+// Projection
+const p0: Record<string, number> = Test.find().projection({
+  age: 1,
+  parent: 1,
+  'docs.id': 1
+});
+const p1: Record<string, number> = Test.find().projection('age docs.id');
+const p2: Record<string, number> | null = Test.find().projection();
+const p3: null = Test.find().projection(null);
+
+
 // Super generic query
 function testGenericQuery(): void {
   interface CommonInterface<T> extends Document {
@@ -184,4 +195,4 @@ function gh10786() {
   if (true) {
     updateQuery.phone = 'XXXX';
   }
-}
\ No newline at end of file
+}

From 63ba06b4ab4cc1b6c57dea9151b517f58d847626 Mon Sep 17 00:00:00 2001
From: Eugene Korshenko <korshenko.ea@gmail.com>
Date: Sun, 16 Jan 2022 16:19:18 +0200
Subject: [PATCH 3/3] types: Weakening of type strictness for ProjectionFields

---
 index.d.ts                 | 2 +-
 test/typescript/queries.ts | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/index.d.ts b/index.d.ts
index c84eb966175..fc68b9b6b26 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -2117,7 +2117,7 @@ declare module 'mongoose' {
 
   type UnpackedIntersection<T, U> = T extends (infer V)[] ? (V & U)[] : T & U;
 
-  type ProjectionFields<DocType> = {[Key in keyof Omit<LeanDocument<DocType>, '__v'>]?: number} & Record<string, number>;
+  type ProjectionFields<DocType> = {[Key in keyof Omit<LeanDocument<DocType>, '__v'>]?: any} & Record<string, any>;
 
   class Query<ResultType, DocType, THelpers = {}, RawDocType = DocType> {
     _mongooseOptions: MongooseQueryOptions;
diff --git a/test/typescript/queries.ts b/test/typescript/queries.ts
index baea0f4063a..6983a84e0f2 100644
--- a/test/typescript/queries.ts
+++ b/test/typescript/queries.ts
@@ -118,7 +118,7 @@ Test.where().find({ name: 'test' });
 
 // Projection
 const p0: Record<string, number> = Test.find().projection({
-  age: 1,
+  age: true,
   parent: 1,
   'docs.id': 1
 });