Merge branch 'master' of github.com:MongoEngine/mongoengine into feature/allow-setting-read-concern-queryset

tests/queryset/test_queryset.py

@@ -4477,6 +4477,74 @@ class TestQueryset(unittest.TestCase):
             expected = "[u'A1', u'A2']"
         assert expected == "%s" % sorted(names)
 
+    def test_fields(self):
+        class Bar(EmbeddedDocument):
+            v = StringField()
+            z = StringField()
+
+        class Foo(Document):
+            x = StringField()
+            y = IntField()
+            items = EmbeddedDocumentListField(Bar)
+
+        Foo.drop_collection()
+
+        Foo(x="foo1", y=1).save()
+        Foo(x="foo2", y=2, items=[]).save()
+        Foo(x="foo3", y=3, items=[Bar(z="a", v="V")]).save()
+        Foo(
+            x="foo4",
+            y=4,
+            items=[
+                Bar(z="a", v="V"),
+                Bar(z="b", v="W"),
+                Bar(z="b", v="X"),
+                Bar(z="c", v="V"),
+            ],
+        ).save()
+        Foo(
+            x="foo5",
+            y=5,
+            items=[
+                Bar(z="b", v="X"),
+                Bar(z="c", v="V"),
+                Bar(z="d", v="V"),
+                Bar(z="e", v="V"),
+            ],
+        ).save()
+
+        foos_with_x = list(Foo.objects.order_by("y").fields(x=1))
+
+        assert all(o.x is not None for o in foos_with_x)
+
+        foos_without_y = list(Foo.objects.order_by("y").fields(y=0))
+
+        assert all(o.y is None for o in foos_with_x)
+
+        foos_with_sliced_items = list(Foo.objects.order_by("y").fields(slice__items=1))
+
+        assert foos_with_sliced_items[0].items == []
+        assert foos_with_sliced_items[1].items == []
+        assert len(foos_with_sliced_items[2].items) == 1
+        assert foos_with_sliced_items[2].items[0].z == "a"
+        assert len(foos_with_sliced_items[3].items) == 1
+        assert foos_with_sliced_items[3].items[0].z == "a"
+        assert len(foos_with_sliced_items[4].items) == 1
+        assert foos_with_sliced_items[4].items[0].z == "b"
+
+        foos_with_elem_match_items = list(
+            Foo.objects.order_by("y").fields(elemMatch__items={"z": "b"})
+        )
+
+        assert foos_with_elem_match_items[0].items == []
+        assert foos_with_elem_match_items[1].items == []
+        assert foos_with_elem_match_items[2].items == []
+        assert len(foos_with_elem_match_items[3].items) == 1
+        assert foos_with_elem_match_items[3].items[0].z == "b"
+        assert foos_with_elem_match_items[3].items[0].v == "W"
+        assert len(foos_with_elem_match_items[4].items) == 1
+        assert foos_with_elem_match_items[4].items[0].z == "b"
+
     def test_elem_match(self):
         class Foo(EmbeddedDocument):
             shape = StringField()