Update SQlAlchemy 1.6 to 2.0 with Type Annotations (#10)

added type annotations

Author: vishalshenoy

sqlalchemy_1.6_to_2.0/README.md

@@ -6,7 +6,7 @@ This example demonstrates how to use Codegen to automatically migrate SQLAlchemy
 
 ## What This Example Does
 
-The migration script handles three key transformations:
+The migration script handles four key transformations:
 
 1. **Convert Query to Select**
    ```python
@@ -43,6 +43,23 @@ The migration script handles three key transformations:
        user = relationship("User", back_populates="addresses")
    ```
 
+4. **Add Type Annotations**
+   ```python
+   # From:
+   class User(Base):
+       __tablename__ = "users"
+       id = Column(Integer, primary_key=True)
+       name = Column(String)
+       addresses = 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()
+   ```
+
 ## Running the Example
 
 ```bash

sqlalchemy_1.6_to_2.0/guide.md

@@ -24,6 +24,15 @@ The migration focuses on these key updates:
    SQLAlchemy 2.0 introduces a new `lazy` parameter for relationship definitions. Update your relationships to use the new `lazy` parameter for improved performance.  
    [Run the Relationship Lazy Loading Codemod](https://www.codegen.sh/search/6512?skillType=codemod)
 
+5. **Type Annotations**
+   SQLAlchemy 2.0 has improved type annotation support. Update your models to include type hints for better IDE support and runtime type checking.
+
+   - Add type annotations to model attributes and relationships
+   - Leverage SQLAlchemy's typing module for proper type hints
+   - Enable better IDE autocompletion and type checking
+
+   [Run the Type Annotations Codemod](https://www.codegen.sh/search/4645?skillType=codemod)
+
 ---
 
 ## How to Migrate
@@ -69,6 +78,17 @@ SQLAlchemy 2.0 introduces a new `lazy` parameter for relationship definitions. U
 
 ---
 
+### Step 5: Add Type Annotations
+SQLAlchemy 2.0 has improved type annotation support. Update your models to include type hints for better IDE support and runtime type checking.
+
+- Add type annotations to model attributes and relationships
+- Leverage SQLAlchemy's typing module for proper type hints
+- Enable better IDE autocompletion and type checking
+
+👉 [Run the Type Annotations Codemod](https://www.codegen.sh/search/4645?skillType=codemod)
+
+---
+
 ## Need Help?
 
 If you encounter issues or have specific edge cases not addressed by the codemods, reach out to the Codegen support team or visit the [Codegen Documentation](https://www.codegen.sh/docs) for detailed guidance.

sqlalchemy_1.6_to_2.0/repo-after/models.py

@@ -1,19 +1,32 @@
+from typing import List, Optional
 from sqlalchemy import Column, Integer, String, ForeignKey
-from sqlalchemy.orm import relationship, backref
+from sqlalchemy.orm import relationship, Mapped, mapped_column
 from database import Base
 
 class Publisher(Base):
     __tablename__ = "publishers"
 
-    id = Column(Integer, primary_key=True, index=True)
-    name = Column(String, unique=True, index=True)
-    books = relationship("Book", back_populates="publisher",lazy='selectin', lazy='selectin')
+    id: Mapped[int] = mapped_column(Integer, primary_key=True, index=True)
+    name: Mapped[str] = mapped_column(String, unique=True, index=True)
+    books: Mapped[List["Book"]] = relationship(
+        "Book", 
+        back_populates="publisher",
+        lazy='selectin'
+    )
 
 class Book(Base):
     __tablename__ = "books"
 
-    id = Column(Integer, primary_key=True, index=True)
-    title = Column(String, index=True)
-    author = Column(String, index=True)
-    description = Column(String)
-    publisher_id = Column(Integer, ForeignKey("publishers.id"))
+    id: Mapped[int] = mapped_column(Integer, primary_key=True, index=True)
+    title: Mapped[str] = mapped_column(String, index=True)
+    author: Mapped[str] = mapped_column(String, index=True)
+    description: Mapped[Optional[str]] = mapped_column(String, nullable=True)
+    publisher_id: Mapped[Optional[int]] = mapped_column(
+        Integer, 
+        ForeignKey("publishers.id"),
+        nullable=True
+    )
+    publisher: Mapped[Optional["Publisher"]] = relationship(
+        "Publisher", 
+        back_populates="books"
+    )