more tests (#1095)

piccolo/query/methods/objects.py

@@ -242,18 +242,22 @@ async def run(
         node: t.Optional[str] = None,
         in_pool: bool = True,
     ) -> t.Optional[ReferencedTable]:
-        references = t.cast(
-            t.Type[ReferencedTable],
-            self.foreign_key._foreign_key_meta.resolved_references,
-        )
+        if not self.row._exists_in_db:
+            raise ValueError("The object doesn't exist in the database.")
+
+        root_table = self.row.__class__
 
         data = (
-            await self.row.__class__.select(
+            await root_table.select(
                 *[
                     i.as_alias(i._meta.name)
                     for i in self.foreign_key.all_columns()
                 ]
             )
+            .where(
+                root_table._meta.primary_key
+                == getattr(self.row, root_table._meta.primary_key._meta.name)
+            )
             .first()
             .run(node=node, in_pool=in_pool)
         )
@@ -262,6 +266,11 @@ async def run(
         if data is None or not any(data.values()):
             return None
 
+        references = t.cast(
+            t.Type[ReferencedTable],
+            self.foreign_key._foreign_key_meta.resolved_references,
+        )
+
         referenced_object = references(**data)
         referenced_object._exists_in_db = True
         return referenced_object

tests/table/instance/test_get_related.py

@@ -10,6 +10,9 @@ class TestGetRelated(AsyncTableTest):
     async def asyncSetUp(self):
         await super().asyncSetUp()
 
+        # Setup two pairs of manager/band, so we can make sure the correct
+        # objects are returned.
+
         self.manager = Manager(name="Guido")
         await self.manager.save()
 
@@ -18,13 +21,25 @@ async def asyncSetUp(self):
         )
         await self.band.save()
 
+        self.manager_2 = Manager(name="Graydon")
+        await self.manager_2.save()
+
+        self.band_2 = Band(
+            name="Rustaceans", manager=self.manager_2.id, popularity=100
+        )
+        await self.band_2.save()
+
     async def test_foreign_key(self) -> None:
         """
         Make sure you can get a related object from another object instance.
         """
         manager = await self.band.get_related(Band.manager)
         assert manager is not None
-        self.assertTrue(manager.name == "Guido")
+        self.assertTrue(manager.id == self.manager.id)
+
+        manager_2 = await self.band_2.get_related(Band.manager)
+        assert manager_2 is not None
+        self.assertTrue(manager_2.id == self.manager_2.id)
 
     async def test_non_foreign_key(self):
         """
@@ -38,7 +53,7 @@ async def test_string(self):
         Make sure it also works using a string representation of a foreign key.
         """
         manager = t.cast(Manager, await self.band.get_related("manager"))
-        self.assertTrue(manager.name == "Guido")
+        self.assertTrue(manager.id == self.manager.id)
 
     async def test_invalid_string(self):
         """
@@ -51,12 +66,33 @@ async def test_multiple_levels(self):
         """
         Make sure ``get_related`` works multiple levels deep.
         """
-        concert = Concert(band_1=self.band)
+        concert = Concert(band_1=self.band, band_2=self.band_2)
         await concert.save()
 
         manager = await concert.get_related(Concert.band_1._.manager)
         assert manager is not None
-        self.assertTrue(manager.name == "Guido")
+        self.assertTrue(manager.id == self.manager.id)
+
+        manager_2 = await concert.get_related(Concert.band_2._.manager)
+        assert manager_2 is not None
+        self.assertTrue(manager_2.id == self.manager_2.id)
 
-        band_2_manager = await concert.get_related(Concert.band_2._.manager)
-        assert band_2_manager is None
+    async def test_no_match(self):
+        """
+        If not related object exists, make sure ``None`` is returned.
+        """
+        concert = Concert(band_1=self.band, band_2=None)
+        await concert.save()
+
+        manager_2 = await concert.get_related(Concert.band_2._.manager)
+        assert manager_2 is None
+
+    async def test_not_in_db(self):
+        """
+        If the object we're calling ``get_related`` on doesn't exist in the
+        database, then make sure an error is raised.
+        """
+        concert = Concert(band_1=self.band, band_2=self.band_2)
+
+        with self.assertRaises(ValueError):
+            await concert.get_related(Concert.band_1._.manager)