test(model): repro #9418

Author: vkarpov15

test/model.populate.test.js

@@ -9171,6 +9171,59 @@ describe('model: populate:', function() {
       assert.equal(docs[1]._id.toString(), p2._id.toString());
       assert.deepEqual(docs[0].children.map(c => c._id), [1]);
       assert.deepEqual(docs[1].children.map(c => c._id), [4]);
+
+      docs = yield Parent.find().sort({ _id: 1 }).
+        populate({ path: 'children', options: { perDocumentLimit: 1 } });
+      assert.equal(docs[0]._id.toString(), p._id.toString());
+      assert.equal(docs[1]._id.toString(), p2._id.toString());
+      assert.deepEqual(docs[0].children.map(c => c._id), [1]);
+      assert.deepEqual(docs[1].children.map(c => c._id), [4]);
+    });
+  });
+
+  it('perDocumentLimit as option to `populate()` method (gh-7318) (gh-9418)', function() {
+    const childSchema = Schema({ _id: Number, parentId: 'ObjectId' });
+
+    const parentSchema = Schema({ name: String });
+    parentSchema.virtual('children', {
+      ref: 'Child',
+      localField: '_id',
+      foreignField: 'parentId',
+      justOne: false,
+      options: { sort: { _id: 1 } }
+    });
+
+    const Child = db.model('Child', childSchema);
+    const Parent = db.model('Parent', parentSchema);
+
+    return co(function*() {
+      const p = yield Parent.create({ name: 'test' });
+
+      yield Child.create([
+        { _id: 1, parentId: p._id },
+        { _id: 2, parentId: p._id },
+        { _id: 3, parentId: p._id }
+      ]);
+
+      const p2 = yield Parent.create({ name: 'test2' });
+      yield Child.create([
+        { _id: 4, parentId: p2._id },
+        { _id: 5, parentId: p2._id }
+      ]);
+
+      let docs = yield Parent.find().sort({ _id: 1 }).
+        populate({ path: 'children', perDocumentLimit: 1 });
+      assert.equal(docs[0]._id.toString(), p._id.toString());
+      assert.equal(docs[1]._id.toString(), p2._id.toString());
+      assert.deepEqual(docs[0].children.map(c => c._id), [1]);
+      assert.deepEqual(docs[1].children.map(c => c._id), [4]);
+
+      docs = yield Parent.find().sort({ _id: 1 }).
+        populate({ path: 'children', options: { perDocumentLimit: 1 } });
+      assert.equal(docs[0]._id.toString(), p._id.toString());
+      assert.equal(docs[1]._id.toString(), p2._id.toString());
+      assert.deepEqual(docs[0].children.map(c => c._id), [1]);
+      assert.deepEqual(docs[1].children.map(c => c._id), [4]);
     });
   });