types: handle buffers in JSONSerialized and fix issue with DocumentArrays

Author: vkarpov15

test/types/schema.test.ts

@@ -1687,12 +1687,13 @@ async function gh14451() {
   const exampleSchema = new Schema({
     myId: { type: 'ObjectId' },
     myRequiredId: { type: 'ObjectId', required: true },
+    myBuf: { type: Buffer, required: true },
     subdoc: {
       type: new Schema({
         subdocProp: Date
       })
-    }
-    // docArr: [{ nums: [Number], times: [Date] }]
+    },
+    docArr: [{ nums: [Number], times: [{ type: Date }] }]
   });
 
   const Test = model('Test', exampleSchema);
@@ -1701,9 +1702,10 @@ async function gh14451() {
   expectType<{
     myId?: string | undefined | null,
     myRequiredId: string,
+    myBuf: { type: 'buffer', data: number[] },
     subdoc?: {
       subdocProp?: string | undefined | null
     } | null,
-    // docArr: { nums: number[], times: string[] }[]
+    docArr: { nums: number[], times: string[] }[]
   }>({} as TestJSON);
 }

types/index.d.ts

@@ -718,6 +718,18 @@ declare module 'mongoose' {
               : BufferToBinary<T[K]>;
   } : T;
 
+  export type BufferToJSON<T> = T extends TreatAsPrimitives ? T : T extends Record<string, any> ? {
+    [K in keyof T]: T[K] extends Buffer
+      ? { type: 'buffer', data: number[] }
+      : T[K] extends (Buffer | null | undefined)
+        ? { type: 'buffer', data: number[] } | null | undefined
+        : T[K] extends Types.DocumentArray<infer ItemType>
+            ? Types.DocumentArray<BufferToBinary<ItemType>>
+            : T[K] extends Types.Subdocument<unknown, unknown, infer SubdocType>
+              ? HydratedSingleSubdocument<SubdocType>
+              : BufferToBinary<T[K]>;
+  } : T;
+
   export type ObjectIdToString<T> = T extends TreatAsPrimitives ? T : T extends Record<string, any> ? {
     [K in keyof T]: T[K] extends mongodb.ObjectId
       ? string
@@ -748,16 +760,18 @@ declare module 'mongoose' {
       : T[K] extends (NativeDate | null | undefined)
         ? string | null | undefined
         : T[K] extends Types.DocumentArray<infer ItemType>
-            ? ItemType
+            ? ItemType[]
             : T[K] extends Types.Subdocument<unknown, unknown, infer SubdocType>
               ? SubdocType
               : SubdocsToPOJOs<T[K]>;
   } : T;
 
   export type JSONSerialized<T> = SubdocsToPOJOs<
     FlattenMaps<
-      ObjectIdToString<
-        DateToString<T>
+      BufferToJSON<
+        ObjectIdToString<
+          DateToString<T>
+        >
       >
     >
   >;