Add run.py for SQL Alchemy 1.6 to 2.0

sqlalchemy_1.6_to_2.0/README.md

@@ -1,64 +1,61 @@
 # SQLAlchemy 1.6 to 2.0 Migration Example
 
-[![Documentation](https://img.shields.io/badge/docs-docs.codegen.com-blue)](https://docs.codegen.com/tutorials/sqlalchemy-1.6-to-2.0)
+This codemod demonstrates how to use Codegen to automatically migrate SQLAlchemy 1.6 code to the new 2.0-style query interface. For a complete walkthrough, check out our [tutorial](https://docs.codegen.com/tutorials/sqlalchemy-1.6-to-2.0).
 
-This example demonstrates how to use Codegen to automatically migrate SQLAlchemy 1.6 code to the new 2.0-style query interface. For a complete walkthrough, check out our [tutorial](https://docs.codegen.com/tutorials/sqlalchemy-1.6-to-2.0).
+## How the Migration Script Works
 
-## What This Example Does
+The codemod script handles four key transformations:
 
-The migration script handles four key transformations:
-
-1. **Convert Query to Select**
+1. **Update Base Class and Imports**
    ```python
    # From:
-   session.query(User).filter_by(name='john').all()
+   from sqlalchemy.ext.declarative import declarative_base
+   Base = declarative_base()
 
    # To:
-   session.execute(
-       select(User).where(User.name == 'john')
-   ).scalars().all()
+   from sqlalchemy.orm import DeclarativeBase
+   class Base(DeclarativeBase):
+       pass
    ```
+   Updates the Base class to use the new DeclarativeBase style.
 
-2. **Update Session Execution**
+2. **Modernize ORM Relationships**
    ```python
    # From:
-   users = session.query(User).all()
-   first_user = session.query(User).first()
+   class User(Base):
+       addresses = relationship("Address", backref="user")
 
    # To:
-   users = session.execute(select(User)).scalars().all()
-   first_user = session.execute(select(User)).scalars().first()
+   class User(Base):
+       addresses = relationship("Address", back_populates="user")
    ```
+   Relationships are modernized to use explicit back_populates instead of backref. If no back reference is specified, it defaults to None.
 
-3. **Modernize ORM Relationships**
+3. **Update Query Method Names**
    ```python
    # From:
-   class User(Base):
-       addresses = relationship("Address", backref="user")
+   db.session.query(User).filter(User.name == 'john').all()
+   db.session.query(User).first()
 
    # To:
-   class User(Base):
-       addresses = relationship("Address", back_populates="user", use_list=True)
-   class Address(Base):
-       user = relationship("User", back_populates="addresses")
+   db.session.select(User).where(User.name == 'john').scalars().all()
+   db.session.select(User).scalar_one_or_none()
    ```
+   Updates query method names to their 2.0 equivalents: `query` → `select`, `filter` → `where`, `all` → `scalars().all`, and `first` → `scalar_one_or_none`.
 
-4. **Add Type Annotations**
+4. **Update Configurations**
    ```python
    # From:
-   class User(Base):
-       __tablename__ = "users"
-       id = Column(Integer, primary_key=True)
-       name = Column(String)
-       addresses = relationship("Address")
+   create_engine(url)
+   sessionmaker(bind=engine)
+   relationship("Address")
 
    # To:
-   class User(Base):
-       __tablename__ = "users"
-       id: Mapped[int] = mapped_column(primary_key=True)
-       name: Mapped[str] = mapped_column()
-       addresses: Mapped[List["Address"]] = relationship()
+   create_engine(url, future=True, pool_pre_ping=True)
+   sessionmaker(bind=engine, future=True)
+   relationship("Address", lazy="select")
    ```
+   Adds future-compatible configurations and default lazy loading settings. Also updates Pydantic configs from `orm_mode` to `from_attributes`.
 
 ## Running the Example
 
@@ -70,13 +67,7 @@ pip install codegen
 python run.py
 ```
 
-The script will process all Python files in the `repo-before` directory and apply the transformations in the correct order.
-
-## Understanding the Code
-
-- `run.py` - The migration script
-- `repo-before/` - Sample SQLAlchemy 1.6 application to migrate
-- `guide.md` - Additional notes and explanations
+The script will process all Python files in the `input_repo` directory and apply the transformations in the correct order.
 
 ## Learn More
 

sqlalchemy_1.6_to_2.0/input_repo/database.py

@@ -3,7 +3,9 @@
 from sqlalchemy.ext.declarative import declarative_base
 from sqlalchemy.orm import sessionmaker
 
-SQLALCHEMY_DATABASE_URL = "postgresql://user:password@localhost/dbname"  # Change to your database URL
+SQLALCHEMY_DATABASE_URL = (
+    "postgresql://user:password@localhost/dbname"  # Change to your database URL
+)
 
 engine = create_engine(SQLALCHEMY_DATABASE_URL)
 SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)

sqlalchemy_1.6_to_2.0/input_repo/models.py

@@ -1,7 +1,8 @@
-from sqlalchemy import Column, Integer, String, ForeignKey, Index
-from sqlalchemy.orm import relationship, backref
+from sqlalchemy import Column, Integer, String, ForeignKey
+from sqlalchemy.orm import relationship
 from database import Base
 
+
 class Publisher(Base):
     __tablename__ = "publishers"