feat: support --fake for aerich upgrade (#398)

* feat: support `--fake` for aerich upgrade

* Add `--fake` to downgrade

* tests: check --fake result for aerich upgrade and downgrade

* Update readme

* Fix unittest failed because of `db_field_types` changed

* refactor: improve type hints and document

tests/assets/fake/_tests.py

@@ -0,0 +1,72 @@
+import pytest
+from models import NewModel
+from models_second import Config
+from settings import TORTOISE_ORM
+from tortoise import Tortoise
+from tortoise.exceptions import OperationalError
+
+
+@pytest.fixture(scope="session")
+def anyio_backend() -> str:
+    return "asyncio"
+
+
+@pytest.fixture(autouse=True)
+async def init_connections():
+    await Tortoise.init(TORTOISE_ORM)
+    try:
+        yield
+    finally:
+        await Tortoise.close_connections()
+
+
+@pytest.mark.anyio
+async def test_init_db():
+    m1 = await NewModel.filter(name="")
+    assert isinstance(m1, list)
+    m2 = await Config.filter(key="")
+    assert isinstance(m2, list)
+    await NewModel.create(name="")
+    await Config.create(key="", label="", value={})
+
+
+@pytest.mark.anyio
+async def test_fake_field_1():
+    assert "field_1" in NewModel._meta.fields_map
+    assert "field_1" in Config._meta.fields_map
+    with pytest.raises(OperationalError):
+        await NewModel.create(name="", field_1=1)
+    with pytest.raises(OperationalError):
+        await Config.create(key="", label="", value={}, field_1=1)
+
+    obj1 = NewModel(name="", field_1=1)
+    with pytest.raises(OperationalError):
+        await obj1.save()
+    obj1 = NewModel(name="")
+    with pytest.raises(OperationalError):
+        await obj1.save()
+    with pytest.raises(OperationalError):
+        obj1 = await NewModel.first()
+    obj1 = await NewModel.all().first().values("id", "name")
+    assert obj1 and obj1["id"]
+
+    obj2 = Config(key="", label="", value={}, field_1=1)
+    with pytest.raises(OperationalError):
+        await obj2.save()
+    obj2 = Config(key="", label="", value={})
+    with pytest.raises(OperationalError):
+        await obj2.save()
+    with pytest.raises(OperationalError):
+        obj2 = await Config.first()
+    obj2 = await Config.all().first().values("id", "key")
+    assert obj2 and obj2["id"]
+
+
+@pytest.mark.anyio
+async def test_fake_field_2():
+    assert "field_2" in NewModel._meta.fields_map
+    assert "field_2" in Config._meta.fields_map
+    with pytest.raises(OperationalError):
+        await NewModel.create(name="")
+    with pytest.raises(OperationalError):
+        await Config.create(key="", label="", value={})