add follow=True for save_related, update docs

docs/models.md

@@ -228,6 +228,33 @@ Each model has a `QuerySet` initialised as `objects` parameter
 !!!info
     To read more about `QuerySets` (including bulk operations) and available methods visit [queries][queries]
 
+## `Model` save status
+
+Each model instance is a separate python object and they do not know anything about each other.
+
+```python
+track1 = await Track.objects.get(name='The Bird')
+track2 = await Track.objects.get(name='The Bird')
+assert track1 == track2 # True
+
+track1.name = 'The Bird2'
+await track1.save()
+assert track1.name == track2.name # False
+# track2 does not update and knows nothing about track1
+```
+
+The objects itself have a saved status, which is set as following:
+
+*  Model is saved after `save/update/load/upsert` method on model
+*  Model is saved after `create/get/first/all/get_or_create/update_or_create` method
+*  Model is saved when passed to `bulk_update` and `bulk_create`
+*  Model is saved after `adding/removing` `ManyToMany` related objects (through model instance auto saved/deleted)
+*  Model is **not** saved after change of any own field (including `pk` as `Model.pk` alias)
+*  Model is **not** saved after adding/removing `ForeignKey` related object (fk column not saved)
+*  Model is **not** saved after instantiation with `__init__` (w/o `QuerySet.create` or before calling `save`)
+
+You can check if model is saved with `ModelInstance.saved` property
+
 ## `Model` methods
 
 ### load
@@ -249,16 +276,57 @@ track.album.name # will return 'Malibu'
 
 ### save
 
+`save() -> self`
+
 You can create new models by using `QuerySet.create()` method or by initializing your model as a normal pydantic model 
 and later calling `save()` method.
 
-`save()` can also be used to persist changes that you made to the model. 
+`save()` can also be used to persist changes that you made to the model, but only if the primary key is not set or the model does not exist in database.
+
+The `save()` method does not check if the model exists in db, so if it does you will get a integrity error from your selected db backend if trying to save model with already existing primary key. 
 
 ```python
 track = Track(name='The Bird')
 await track.save() # will persist the model in database
+
+track = await Track.objects.get(name='The Bird')
+await track.save() # will raise integrity error as pk is populated
 ```
 
+### update
+
+`update(**kwargs) -> self`
+
+You can update models by using `QuerySet.update()` method or by updating your model attributes (fields) and calling `update()` method.
+
+If you try to update a model without a primary key set a `ModelPersistenceError` exception will be thrown.
+
+To persist a newly created model use `save()` or `upsert(**kwargs)` methods.
+
+```python
+track = await Track.objects.get(name='The Bird')
+await track.update(name='The Bird Strikes Again')
+```
+
+### upsert
+
+`upsert(**kwargs) -> self`
+
+It's an proxy to either `save()` or `update(**kwargs)` methods described above.
+
+If the primary key is set -> the `update` method will be called.
+
+If the pk is not set the `save()` method will be called.
+
+```python
+track = Track(name='The Bird')
+await track.upsert() # will call save as the pk is empty
+
+track = await Track.objects.get(name='The Bird')
+await track.upsert(name='The Bird Strikes Again') # will call update as pk is already populated
+```
+
+
 ### delete
 
 You can delete models by using `QuerySet.delete()` method or by using your model and calling `delete()` method.
@@ -271,13 +339,28 @@ await track.delete() # will delete the model from database
 !!!tip
     Note that that `track` object stays the same, only record in the database is removed.
 
-### update
+### save_related
 
-You can delete models by using `QuerySet.update()` method or by using your model and calling `update()` method.
+`save_related(follow: bool = False) -> None`
+
+Method goes through all relations of the `Model` on which the method is called, 
+and calls `upsert()` method on each model that is **not** saved. 
+
+To understand when a model is saved check [save status][save status] section above.
+
+By default the `save_related` method saved only models that are directly related (one step away) to the model on which the method is called.
+
+But you can specify the `follow=True` parameter to traverse through nested models and save all of them in the relation tree.
+
+!!!warning
+    To avoid circular updates with `follow=True` set, `save_related` keeps a set of already visited Models, 
+    and won't perform nested `save_related` on Models that were already visited.
+    
+    So if you have a diamond or circular relations types you need to perform the updates in a manual way.
     
     ```python
-track = await Track.objects.get(name='The Bird')
+    # in example like this the second Street (coming from Company) won't be save_related, so Whatever won't be updated
-await track.update(name='The Bird Strikes Again')
+    Street -> District -> City -> Companies -> Street -> Whatever
     ```
 
 ## Internals
@@ -348,3 +431,4 @@ For example to list table model fields you can:
 [sqlalchemy connection string]: https://docs.sqlalchemy.org/en/13/core/engines.html#database-urls
 [sqlalchemy table creation]: https://docs.sqlalchemy.org/en/13/core/metadata.html#creating-and-dropping-database-tables
 [alembic]: https://alembic.sqlalchemy.org/en/latest/tutorial.html
+[save status]:  ../models/#model-save-status

ormar/models/model.py

@@ -1,5 +1,16 @@
 import itertools
-from typing import Any, Dict, List, Optional, Set, TYPE_CHECKING, Type, TypeVar, Union
+from typing import (
+    Any,
+    Dict,
+    List,
+    Optional,
+    Set,
+    TYPE_CHECKING,
+    Tuple,
+    Type,
+    TypeVar,
+    Union,
+)
 
 import sqlalchemy
 
@@ -192,22 +203,47 @@ class Model(NewBaseModel):
         self.set_save_status(True)
         return self
 
-    async def save_related(self) -> int:  # noqa: CCR001
+    async def save_related(  # noqa: CCR001
-        update_count = 0
+        self, follow: bool = False, visited: Set = None, update_count: int = 0
+    ) -> int:  # noqa: CCR001
+        if not visited:
+            visited = {self.__class__}
+        else:
+            visited = {x for x in visited}
+            visited.add(self.__class__)
+
         for related in self.extract_related_names():
             if self.Meta.model_fields[related].virtual or issubclass(
                 self.Meta.model_fields[related], ManyToManyField
             ):
                 for rel in getattr(self, related):
-                    if not rel.saved:
+                    update_count, visited = await self._update_and_follow(
-                        await rel.upsert()
+                        rel=rel,
-                        update_count += 1
+                        follow=follow,
+                        visited=visited,
+                        update_count=update_count,
+                    )
+                visited.add(self.Meta.model_fields[related].to)
             else:
                 rel = getattr(self, related)
+                update_count, visited = await self._update_and_follow(
+                    rel=rel, follow=follow, visited=visited, update_count=update_count
+                )
+                visited.add(rel.__class__)
+        return update_count
+
+    @staticmethod
+    async def _update_and_follow(
+        rel: "Model", follow: bool, visited: Set, update_count: int
+    ) -> Tuple[int, Set]:
+        if follow and rel.__class__ not in visited:
+            update_count = await rel.save_related(
+                follow=follow, visited=visited, update_count=update_count
+            )
         if not rel.saved:
             await rel.upsert()
             update_count += 1
-        return update_count
+        return update_count, visited
 
     async def update(self: T, **kwargs: Any) -> T:
         if kwargs:

tests/test_save_related.py

@@ -11,6 +11,16 @@ database = databases.Database(DATABASE_URL, force_rollback=True)
 metadata = sqlalchemy.MetaData()
 
 
+class CringeLevel(ormar.Model):
+    class Meta:
+        tablename = "levels"
+        metadata = metadata
+        database = database
+
+    id: int = ormar.Integer(primary_key=True)
+    name: str = ormar.String(max_length=100)
+
+
 class NickNames(ormar.Model):
     class Meta:
         tablename = "nicks"
@@ -20,6 +30,7 @@ class NickNames(ormar.Model):
     id: int = ormar.Integer(primary_key=True)
     name: str = ormar.String(max_length=100, nullable=False, name="hq_name")
     is_lame: bool = ormar.Boolean(nullable=True)
+    level: CringeLevel = ormar.ForeignKey(CringeLevel)
 
 
 class NicksHq(ormar.Model):
@@ -82,7 +93,7 @@ async def test_saving_related_fk_rel():
 
 
 @pytest.mark.asyncio
-async def test_adding_many_to_many_does_not_gets_dirty():
+async def test_saving_many_to_many():
     async with database:
         async with database.transaction(force_rollback=True):
             nick1 = await NickNames.objects.create(name="BazingaO", is_lame=False)
@@ -111,7 +122,7 @@ async def test_adding_many_to_many_does_not_gets_dirty():
 
 
 @pytest.mark.asyncio
-async def test_queryset_methods():
+async def test_saving_reversed_relation():
     async with database:
         async with database.transaction(force_rollback=True):
             hq = await HQ.objects.create(name="Main")
@@ -149,3 +160,47 @@ async def test_queryset_methods():
             assert count == 2
             assert hq.companies[0].saved
             assert hq.companies[1].saved
+
+
+@pytest.mark.asyncio
+async def test_saving_nested():
+    async with database:
+        async with database.transaction(force_rollback=True):
+            level = await CringeLevel.objects.create(name='High')
+            level2 = await CringeLevel.objects.create(name='Low')
+            nick1 = await NickNames.objects.create(name="BazingaO", is_lame=False, level=level)
+            nick2 = await NickNames.objects.create(name="Bazinga20", is_lame=True, level=level2)
+
+            hq = await HQ.objects.create(name="Main")
+            assert hq.saved
+
+            await hq.nicks.add(nick1)
+            assert hq.saved
+            await hq.nicks.add(nick2)
+            assert hq.saved
+
+            count = await hq.save_related()
+            assert count == 0
+
+            hq.nicks[0].level.name = "Medium"
+            assert not hq.nicks[0].level.saved
+            assert hq.nicks[0].saved
+
+            count = await hq.save_related(follow=True)
+            assert count == 1
+            assert hq.nicks[0].saved
+            assert hq.nicks[0].level.saved
+
+            hq.nicks[0].level.name = "Low"
+            hq.nicks[1].level.name = "Medium"
+            assert not hq.nicks[0].level.saved
+            assert not hq.nicks[1].level.saved
+            assert hq.nicks[0].saved
+            assert hq.nicks[1].saved
+
+            count = await hq.save_related(follow=True)
+            assert count == 2
+            assert hq.nicks[0].saved
+            assert hq.nicks[0].level.saved
+            assert hq.nicks[1].saved
+            assert hq.nicks[1].level.saved