fix potential issue with setting geoNear.query to undefined (#6696)

* add test cases for geoNear aggregation

Test cases do not have the `query` parameter set in $geoNear aggregation stage. this is to test for a reported potential issue when the parameter is not set.

* fixed potential issue when setting the geoNear.query parameter to undefined

see dicussion in https://github.com/parse-community/parse-server/pull/6540

* fixed duplicate index name in test

spec/ParseQuery.Aggregate.spec.js

@@ -1430,7 +1430,7 @@ describe('Parse.Query Aggregate testing', () => {
     }
   );
 
-  it_only_db('mongo')('geoNear with location query', async () => {
+  it_only_db('mongo')('aggregate geoNear with location query', async () => {
     // Create geo index which is required for `geoNear` query
     const database = Config.get(Parse.applicationId).database;
     const schema = await new Parse.Schema('GeoObject').save();
@@ -1438,7 +1438,7 @@ describe('Parse.Query Aggregate testing', () => {
       'GeoObject',
       schema,
       ['location'],
-      'geoIndex',
+      undefined,
       false,
       { indexType: '2dsphere' },
     );
@@ -1474,4 +1474,77 @@ describe('Parse.Query Aggregate testing', () => {
     expect(results[0].value).toEqual(2);
     expect(results[1].value).toEqual(3);
   });
+
+  it_only_db('mongo')('aggregate geoNear with near GeoJSON point', async () => {
+    // Create geo index which is required for `geoNear` query
+    const database = Config.get(Parse.applicationId).database;
+    const schema = await new Parse.Schema('GeoObject').save();
+    await database.adapter.ensureIndex(
+      'GeoObject',
+      schema,
+      ['location'],
+      undefined,
+      false,
+      '2dsphere'
+    );
+    // Create objects
+    const GeoObject = Parse.Object.extend('GeoObject');
+    const obj1 = new GeoObject({ value: 1, location: new Parse.GeoPoint(1, 1), date: new Date(1) });
+    const obj2 = new GeoObject({ value: 2, location: new Parse.GeoPoint(2, 1), date: new Date(2) });
+    const obj3 = new GeoObject({ value: 3, location: new Parse.GeoPoint(3, 1), date: new Date(3) });
+    await Parse.Object.saveAll([obj1, obj2, obj3]);
+    // Create query
+    const pipeline = [
+      {
+        geoNear: {
+          near: {
+            type: 'Point',
+            coordinates: [1, 1]
+          },
+          key: 'location',
+          spherical: true,
+          distanceField: 'dist'
+        }
+      }
+    ];
+    const query = new Parse.Query(GeoObject);
+    const results = await query.aggregate(pipeline);
+    // Check results
+    expect(results.length).toEqual(3);
+  });
+
+  it_only_db('mongo')('aggregate geoNear with near legacy coordinate pair', async () => {
+    // Create geo index which is required for `geoNear` query
+    const database = Config.get(Parse.applicationId).database;
+    const schema = await new Parse.Schema('GeoObject').save();
+    await database.adapter.ensureIndex(
+      'GeoObject',
+      schema,
+      ['location'],
+      undefined,
+      false,
+      '2dsphere'
+    );
+    // Create objects
+    const GeoObject = Parse.Object.extend('GeoObject');
+    const obj1 = new GeoObject({ value: 1, location: new Parse.GeoPoint(1, 1), date: new Date(1) });
+    const obj2 = new GeoObject({ value: 2, location: new Parse.GeoPoint(2, 1), date: new Date(2) });
+    const obj3 = new GeoObject({ value: 3, location: new Parse.GeoPoint(3, 1), date: new Date(3) });
+    await Parse.Object.saveAll([obj1, obj2, obj3]);
+    // Create query
+    const pipeline = [
+      {
+        geoNear: {
+          near: [1, 1],
+          key: 'location',
+          spherical: true,
+          distanceField: 'dist'
+        }
+      }
+    ];
+    const query = new Parse.Query(GeoObject);
+    const results = await query.aggregate(pipeline);
+    // Check results
+    expect(results.length).toEqual(3);
+  });
 });

src/Adapters/Storage/Mongo/MongoStorageAdapter.js

@@ -860,7 +860,7 @@ export class MongoStorageAdapter implements StorageAdapter {
           stage.$project
         );
       }
-      if (stage.$geoNear) {
+      if (stage.$geoNear && stage.$geoNear.query) {
         stage.$geoNear.query = this._parseAggregateArgs(
           schema,
           stage.$geoNear.query