version with pydantic inheritance passing all the tests

tests/test_same_table_joins.py

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+import asyncio
+
+import databases
+import pytest
+import sqlalchemy
+
+import ormar
+from tests.settings import DATABASE_URL
+
+database = databases.Database(DATABASE_URL, force_rollback=True)
+metadata = sqlalchemy.MetaData()
+
+
+class Department(ormar.Model):
+    class Meta:
+        tablename = "departments"
+        metadata = metadata
+        database = database
+
+    id: ormar.Integer(primary_key=True, autoincrement=False)
+    name: ormar.String(max_length=100)
+
+
+class SchoolClass(ormar.Model):
+    class Meta:
+        tablename = "schoolclasses"
+        metadata = metadata
+        database = database
+
+    id: ormar.Integer(primary_key=True)
+    name: ormar.String(max_length=100)
+    department: ormar.ForeignKey(Department, nullable=False)
+
+
+class Category(ormar.Model):
+    class Meta:
+        tablename = "categories"
+        metadata = metadata
+        database = database
+
+    id: ormar.Integer(primary_key=True)
+    name: ormar.String(max_length=100)
+
+
+class Student(ormar.Model):
+    class Meta:
+        tablename = "students"
+        metadata = metadata
+        database = database
+
+    id: ormar.Integer(primary_key=True)
+    name: ormar.String(max_length=100)
+    schoolclass: ormar.ForeignKey(SchoolClass)
+    category: ormar.ForeignKey(Category, nullable=True)
+
+
+class Teacher(ormar.Model):
+    class Meta:
+        tablename = "teachers"
+        metadata = metadata
+        database = database
+
+    id: ormar.Integer(primary_key=True)
+    name: ormar.String(max_length=100)
+    schoolclass: ormar.ForeignKey(SchoolClass)
+    category: ormar.ForeignKey(Category, nullable=True)
+
+
+@pytest.fixture(scope="module")
+def event_loop():
+    loop = asyncio.get_event_loop()
+    yield loop
+    loop.close()
+
+
+@pytest.fixture(autouse=True, scope="module")
+async def create_test_database():
+    engine = sqlalchemy.create_engine(DATABASE_URL)
+    metadata.create_all(engine)
+    department = await Department.objects.create(id=1, name="Math Department")
+    class1 = await SchoolClass.objects.create(name="Math", department=department)
+    category = await Category.objects.create(name="Foreign")
+    category2 = await Category.objects.create(name="Domestic")
+    await Student.objects.create(name="Jane", category=category, schoolclass=class1)
+    await Student.objects.create(name="Jack", category=category2, schoolclass=class1)
+    await Teacher.objects.create(name="Joe", category=category2, schoolclass=class1)
+    yield
+    metadata.drop_all(engine)
+
+
+@pytest.mark.asyncio
+async def test_model_multiple_instances_of_same_table_in_schema():
+    async with database:
+        classes = await SchoolClass.objects.select_related(
+            ["teachers__category", "students"]
+        ).all()
+        assert classes[0].name == "Math"
+        assert classes[0].students[0].name == "Jane"
+
+        assert len(classes[0].dict().get("students")) == 2
+
+        # related fields of main model are only populated by pk
+        # unless there is a required foreign key somewhere along the way
+        # since department is required for schoolclass it was pre loaded (again)
+        # but you can load them anytime
+        assert classes[0].students[0].schoolclass.name == "Math"
+        assert classes[0].students[0].schoolclass.department.name is None
+        await classes[0].students[0].schoolclass.department.load()
+        assert classes[0].students[0].schoolclass.department.name == "Math Department"
+
+
+@pytest.mark.asyncio
+async def test_right_tables_join():
+    async with database:
+        classes = await SchoolClass.objects.select_related(
+            ["teachers__category", "students"]
+        ).all()
+        assert classes[0].teachers[0].category.name == "Domestic"
+
+        assert classes[0].students[0].category.name is None
+        await classes[0].students[0].category.load()
+        assert classes[0].students[0].category.name == "Foreign"
+
+
+@pytest.mark.asyncio
+async def test_multiple_reverse_related_objects():
+    async with database:
+        classes = await SchoolClass.objects.select_related(
+            ["teachers__category", "students__category"]
+        ).all()
+        assert classes[0].name == "Math"
+        assert classes[0].students[1].name == "Jack"
+        assert classes[0].teachers[0].category.name == "Domestic"