for now revert type changes to avoid mypy errors, add validation for through models, clean docs etc

tests/test_m2m_through_fields.py

@@ -375,25 +375,3 @@ async def test_excluding_fields_on_through_model() -> Any:
         for category in post3.categories:
             assert category.postcategory.param_name is None
             assert category.postcategory.sort_order is None
-
-
-# TODO: check/ modify following
-
-# add to fields with class lower name (V)
-# forward refs update (V)
-# creating while adding to relation (kwargs in add) (V)
-# creating in queryset proxy (dict with through name and kwargs) (V)
-# loading the data into model instance of though model (V) <- fix fields ane exclude
-# accessing from instance (V) <- no both sides only nested one is relevant, fix one side
-# filtering in filter (through name normally) (V) < - table prefix from normal relation,
-#               check if is_through needed, resolved side of relation
-# ordering by in order_by (V)
-# updating in query (V)
-# updating from querysetproxy (V)
-# including/excluding in fields? (V)
-# make through optional? auto-generated for cases other fields are missing? (V)
-
-# modifying from instance (both sides?) (X) <= no, the loaded one doesn't have relations
-# allowing to change fk fields names in through model? (X) <= separate issue
-
-# prevent adding relation on through field definition

tests/test_through_relations_fail.py

@@ -0,0 +1,51 @@
+# type: ignore
+
+import databases
+import pytest
+import sqlalchemy
+
+import ormar
+from ormar import ModelDefinitionError
+from tests.settings import DATABASE_URL
+
+database = databases.Database(DATABASE_URL, force_rollback=True)
+metadata = sqlalchemy.MetaData()
+
+
+def test_through_with_relation_fails():
+    class BaseMeta(ormar.ModelMeta):
+        database = database
+        metadata = metadata
+
+    class Category(ormar.Model):
+        class Meta(BaseMeta):
+            tablename = "categories"
+
+        id = ormar.Integer(primary_key=True)
+        name = ormar.String(max_length=40)
+
+    class Blog(ormar.Model):
+        class Meta(BaseMeta):
+            pass
+
+        id: int = ormar.Integer(primary_key=True)
+        title: str = ormar.String(max_length=200)
+
+    class PostCategory(ormar.Model):
+        class Meta(BaseMeta):
+            tablename = "posts_x_categories"
+
+        id: int = ormar.Integer(primary_key=True)
+        sort_order: int = ormar.Integer(nullable=True)
+        param_name: str = ormar.String(default="Name", max_length=200)
+        blog = ormar.ForeignKey(Blog)
+
+    with pytest.raises(ModelDefinitionError):
+
+        class Post(ormar.Model):
+            class Meta(BaseMeta):
+                pass
+
+            id: int = ormar.Integer(primary_key=True)
+            title: str = ormar.String(max_length=200)
+            categories = ormar.ManyToMany(Category, through=PostCategory)