✨ Support Annotated approach for Relationship attributes

[bolu61]

see #229 (comment)

I'm not really sure how Pydantic does it, but here's a potential workaround to the problem.

[YuriiMotov]

@bolu61, thanks for working on this!

So, this PR fixes the following code example:

class Foo(SQLModel, table=True):
    id: Annotated[int | None, Field(primary_key=True)] = None
    uuid: Annotated[UUID, Field(unique=True)]

class Bar(SQLModel, table=True):
    id: Annotated[int | None, Field(primary_key=True)] = None
    uuid: Annotated[UUID, Field(unique=True)]
    foo_id: Annotated[int, Field(foreign_key="foo.id")]
    foo: Annotated[Foo, Relationship()]

For now last line (with Relationship()) doesn't work (ValueError: <class '__main__.Foo'> has no matching SQLAlchemy type) and this PR fixes that.

I think this is not the same that was initially proposed in #229. The idea there was to support passing multiple annotations like:

class Hero(SQLModel, table=True):
    id: Annotated[Optional[int], Field(examples=....), Column(primary_key=True)] = None

Where Field can be pydantic.Field.
So, I suggest we unmark this PR as the one that resolves that issue.

As for changes introduced by this PR, I think it goes in line with modern recommendations to use Annotated approach instead parameterizing fields via default value.
I think we should test this approach more and add some automatic tests. Then it will have all chances to be accepted.

[bolu61]

@YuriiMotov I agree.

I'm not too familiar with this codebase. Can you point me to where I can write those tests?

[YuriiMotov]

I'm not too familiar with this codebase. Can you point me to where I can write those tests?

You can create an annotated version of the code example from "Relationships" section of docs:

• Go to https://github.com/fastapi/sqlmodel/tree/main/docs_src/tutorial/relationship_attributes/define_relationship_attributes
• Create a copy of tutorial001_py310.py, call it tutorial001_an_py310.py
• Edit code to follow the Annotated approach
• Go to https://github.com/fastapi/sqlmodel/tree/main/tests/test_tutorial/test_relationship_attributes/test_define_relationship_attributes
• Create a copy of test_tutorial001_py310.py, call it test_tutorial001_an_py310.py
• Update code to import app from tutorial001_an_py310.py
• Push changes and check that new version of code example appeared in "Other versions and variants"

[github-actions]

📝 Docs preview

Last commit de8a2f4 at: https://1bbba862.sqlmodel.pages.dev

[svlandeg]

The test that was failing previously is now fixed thanks to #1607.

@YuriiMotov : do you want to give this another review?