| name | returns |
| description | Guardrail for dry-python/returns in pawrrtal. Use when an agent proposes Maybe, Result, IOResult, FutureResult, railway-oriented error handling, or adding the returns dependency. |
| paths | ["backend/**/*.py","backend/pyproject.toml"] |
returns for pawrrtal
dry-python/returns is not part of this backend. The backend
restructure explicitly removed the dependency and chose idiomatic
Python error handling instead.
Rule
Do not add returns, Maybe, Result, IOResult, or
FutureResult to Pawrrtal code. Do not pin returns in
backend/pyproject.toml, enable the returns mypy plugin, or wrap
provider/chat/router contracts in railway containers.
Use the local patterns instead:
| Need | Use |
|---|
| Route failures | HTTPException at the route boundary |
| Provider/runtime failures | Narrow exception classes plus clear SSE/error events |
| Optional database rows | `T |
| Validation | Pydantic models, typed helpers, and explicit exceptions |
| Async multi-step flows | Small helpers with try/except at the orchestration boundary |
Review checklist
- Reject new
from returns... imports.
- Reject
Result[T, E], Maybe[T], IOResult[...], and
FutureResult[...] signatures.
- Reject mypy plugin entries for
returns.contrib.mypy.returns_plugin.
- If a proposal says "pilot returns", redirect it to a separate design
discussion before code changes.
The previous pilot notes are archived in git history; they are not an
active implementation plan.
