fix: cursor returns generic doc

Author: nbbeeken

src/cursor/aggregation_cursor.ts

@@ -152,7 +152,7 @@ export class AggregationCursor<TSchema = Document> extends AbstractCursor<TSchem
    *   );
    * ```
    */
-  project<T = TSchema>($project: Document): AggregationCursor<T>;
+  project<T = Document>($project: Document): AggregationCursor<T>;
   project($project: Document): this {
     assertUninitialized(this);
     this[kPipeline].push({ $project });

src/cursor/find_cursor.ts

@@ -361,7 +361,7 @@ export class FindCursor<TSchema = Document> extends AbstractCursor<TSchema> {
    *   );
    * ```
    */
-  project<T = TSchema>(value: Document): FindCursor<T>;
+  project<T = Document>(value: Document): FindCursor<T>;
   project(value: Document): this {
     assertUninitialized(this);
     this[kBuiltOptions].projection = value;

src/operations/find.ts

@@ -16,7 +16,10 @@ import { isSharded } from '../cmap/wire_protocol/shared';
 import { ReadConcern } from '../read_concern';
 import type { ClientSession } from '../sessions';
 
-/** @public */
+/**
+ * @public
+ * @typeParam TSchema - Unused schema definition, deprecated usage, only specify `FindOptions` with no generic
+ */
 // eslint-disable-next-line @typescript-eslint/no-unused-vars
 export interface FindOptions<TSchema extends Document = Document> extends CommandOperationOptions {
   /** Sets the limit of documents returned in the query. */

test/types/community/collection/findX.test-d.ts

@@ -128,7 +128,8 @@ const optionsWithProjection: FindOptions = {
   }
 };
 
-expectNotType<FindOptions>({
+// this is changed in NODE-3454 to be the opposite test since Projection is flexible now
+expectAssignable<FindOptions>({
   projection: {
     make: 'invalid'
   }

test/types/community/cursor.test-d.ts

@@ -22,7 +22,7 @@ const cursor = collection
   .min({ age: 18 })
   .maxAwaitTimeMS(1)
   .maxTimeMS(1)
-  .project({})
+  // .project({}) -> projections removes the types from the returned documents
   .returnKey(true)
   .showRecordId(true)
   .skip(1)
@@ -31,6 +31,7 @@ const cursor = collection
 
 expectType<FindCursor<{ foo: number }>>(cursor);
 expectType<Readable>(cursor.stream());
+expectType<FindCursor<Document>>(cursor.project({}));
 
 collection.find().project({});
 collection.find().project({ notExistingField: 1 });
@@ -118,7 +119,7 @@ interface PublicMeme {
   likes: number;
   someRandomProp: boolean; // Projection makes no enforcement on anything
   // the convenience parameter project<X>() allows you to define a return type,
-  // otherwise projections returns your schema
+  // otherwise projections returns generic document
 }
 
 const publicMemeProjection = {
@@ -132,18 +133,14 @@ const memeCollection = new Db(new MongoClient(''), '').collection<InternalMeme>(
 expectType<PublicMeme[]>(
   await memeCollection
     .find({ _id: { $in: [] } })
-    .sort({ _id: -1 })
-    .limit(3)
     .project<PublicMeme>(publicMemeProjection) // <== Argument of type T is not assignable to parameter of type U
     .toArray()
 );
 
-// Returns you're untouched schema when no override given
-expectType<InternalMeme[]>(
+// Returns generic document when no override given
+expectNotType<InternalMeme[]>(
   await memeCollection
     .find({ _id: { $in: [] } })
-    .sort({ _id: -1 })
-    .limit(3)
     .project(publicMemeProjection) // <== Argument of type T is not assignable to parameter of type U
     .toArray()
 );
@@ -153,8 +150,6 @@ expectType<Document[]>(
   await new Db(new MongoClient(''), '')
     .collection('memes')
     .find({ _id: { $in: [] } })
-    .sort({ _id: -1 })
-    .limit(3)
     .project(publicMemeProjection) // <== Argument of type T is not assignable to parameter of type U
     .toArray()
 );