refactor(NODE-6146): put cursor response back under a flag (#4098)

Author: nbbeeken

src/cursor/find_cursor.ts

@@ -81,6 +81,9 @@ export class FindCursor<TSchema = any> extends AbstractCursor<TSchema> {
     // the response is not a cursor when `explain` is enabled
     if (CursorResponse.is(response)) {
       this[kNumReturned] = response.batchSize;
+    } else {
+      // Can be an explain response, hence the ?. on everything
+      this[kNumReturned] = this[kNumReturned] + (response?.cursor?.firstBatch?.length ?? 0);
     }
 
     // TODO: NODE-2882
@@ -114,10 +117,12 @@ export class FindCursor<TSchema = any> extends AbstractCursor<TSchema> {
       }
     }
 
-    const response = await super.getMore(batchSize, this.client.autoEncrypter ? false : true);
+    const response = await super.getMore(batchSize, false);
     // TODO: wrap this in some logic to prevent it from happening if we don't need this support
     if (CursorResponse.is(response)) {
       this[kNumReturned] = this[kNumReturned] + response.batchSize;
+    } else {
+      this[kNumReturned] = this[kNumReturned] + (response?.cursor?.nextBatch?.length ?? 0);
     }
 
     return response;

src/operations/find.ts

@@ -1,5 +1,4 @@
 import type { Document } from '../bson';
-import { CursorResponse } from '../cmap/wire_protocol/responses';
 import { MongoInvalidArgumentError } from '../error';
 import { ReadConcern } from '../read_concern';
 import type { Server } from '../sdam/server';
@@ -115,7 +114,7 @@ export class FindOperation extends CommandOperation<Document> {
         documentsReturnedIn: 'firstBatch',
         session
       },
-      this.explain ? undefined : CursorResponse
+      undefined
     );
   }
 }