Claude Code: Lessons from the Trenches

claude

Add more logging to books_api
- info for starting/ending of requests.
- debug for any db interaction

Done. I've added logging to the books_api:

  Info logging for requests (routes.py):
  - All endpoints now log "request started" at the beginning
  - All endpoints log "request completed" at the end

  Debug logging for DB interactions (db/books.py):
  - get_all_books: logs query start and number of books retrieved
  - get_book_by_id: logs query and whether book was found
  - create_book: logs the data being created and the resulting book id

# books-api

- Run `just typecheck` after making changes
- Run `just fmt` to format code
- These can be run without asking permission

I can see the logger is already set up. I'll add the logging statements.
...
Now I'll run typecheck and format as per the project instructions.
...
Bash(just typecheck)
Bash(just fmt)
...
Done. Typecheck passed and code was formatted.

Add a PATCH books endpoint.
Update the README.md, .http file, tests and src
Create a plan for the changes above and ask me to approve it before making the changes.

PATCH /books/{book_id} Implementation Plan

Files to modify (6 total):
┌─────────────────┬─────────────────────────────────────────────────────────────┐
│      File       │                           Change                            │
├─────────────────┼─────────────────────────────────────────────────────────────┤
│ schemas.py      │ Add BookUpdate model with all optional fields               │
│ routes.py       │ Add PATCH endpoint using existing update_book() db function │
│ README.md       │ Document the new endpoint                                   │
│ .http           │ Add PATCH request examples                                  │
│ test_routes.py  │ Add TestPatchBook class with 4 test cases                   │
│ test_schemas.py │ Add tests for BookUpdate schema                             │
└─────────────────┴─────────────────────────────────────────────────────────────┘

Key details:
- Uses existing update_book() function from db layer
- Returns 404 if book not found
- Returns the updated book as BookResponse

/agent

You are an expert bug fixer that uses TDD approach: write test, fix bug, see test pass.

There is a bug in the code, I see two times the same book title in the database.

I'll use the bug-fixer-tdd agent to investigate and fix the duplicate books issue.
...
bug-fixer-tdd(Fix duplicate books bug)
...
The bug has been fixed:

  Problem: The Book model had no unique constraint on the title field.

  Fix: Added unique=True to the title column in models/books.py:10:
  title: Mapped[str] = mapped_column(String(255), nullable=False, unique=True)

  Test added: test_cannot_create_duplicate_book_with_same_title verifies
  that attempting to create a duplicate book now raises IntegrityError.

  All 50 tests pass, typecheck passes, and formatting is correct.

# Project Structure

When creating new REST resources, follow this structure:

./books-api/src/books_api
./http/MODEL/routes # REST API endpoints
./http/MODEL/schemas # Request/Response schemas
./models/MODEL # Pydantic models
./db/MODEL.py # Database operations

Mirror this structure in the test directory.

Can you create the CRUD operations for users, borrowings.
Users can borrow books.

Users (/users)
- Model: models/users.py - User with id, name, email fields
- DB operations: db/users.py - CRUD functions
- HTTP endpoints: GET, POST, PATCH, DELETE

Borrowings (/borrowings)
- Model: models/borrowings.py - Borrowing with user_id, book_id, timestamps
- DB operations: db/borrowings.py - CRUD + return_book function
- HTTP endpoints: full CRUD + POST /borrowings/{id}/return

Tests created following existing patterns. Typecheck and formatting passed.

{
  "mcpServers": {
    "books": {
      "type": "sse",
      "url": "http://localhost:8080/sse"
    }
  }
}

What books are available in the books-mcp?
Can you add them to our books-api?
Can you then use the api to list the books?

I found 5 books in the books-mcp:
┌───────────────────────────────────┬────────────────────────┬──────┐
│             Title                 │         Author         │ Year │
├───────────────────────────────────┼────────────────────────┼──────┤
│ To Kill a Mockingbird             │ Harper Lee             │ 1960 │
│ 1984                              │ George Orwell          │ 1949 │
│ Pride and Prejudice               │ Jane Austen            │ 1813 │
│ The Great Gatsby                  │ F. Scott Fitzgerald    │ 1925 │
│ One Hundred Years of Solitude     │ Gabriel Garcia Marquez │ 1967 │
└───────────────────────────────────┴────────────────────────┴──────┘

Done. I:
1. Queried the books-mcp using the MCP tool and found 5 books
2. Added all 5 books to the books-api via POST requests
3. Listed the books from the API - all 5 books are now available

Can you implement ticket DEV-4.
- Create a branch dev-4
- For each task in the epic:
  - Create a commit with implementation

I found the epic. DEV-4: Add book type requires:
- Adding a book type field (fiction, non_fiction, unknown)
- Maintaining 80% code coverage

Found 2 tasks:
1. DEV-5: Update db schema (use enums)
2. DEV-6: Update REST endpoints (default to unknown)

commit f5902a4 (HEAD -> dev-4)
    DEV-6: Update REST endpoints for books to include book_type
    Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

commit 8e60b64
    DEV-5: Update db schema of books to include book_type
    Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

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