REST API Service

rest_api_service — ground rules

Multi-file output. Layout:

main.py              # FastAPI app + routes
models.py            # Pydantic schemas
storage.py           # in-memory or sqlite3 backend (no SQLAlchemy)
test_main.py         # pytest suite
requirements.txt     # fastapi + uvicorn + pytest + pytest-asyncio (pinned)

The Cycle D sandbox accepts an additional_files JSON metadata field — use it to split files cleanly. If multi-file isn't an option, fall through to a single main.py with everything inline.

Route contract (per resource — example: items)

• GET /items → list (paginated via ?skip=0&limit=50)
• GET /items/{id} → single (404 with descriptive detail)
• POST /items → create (201 Created, returns the created resource)
• PUT /items/{id} → update (200 OK, full replace)
• DELETE /items/{id} → delete (204 No Content)

Validation

• Pydantic v2 schemas. Constraints inline via Field(..., min_length=..., max_length=..., ge=..., le=...).
• 422 errors keep FastAPI's default shape (loc + msg + type).
• Custom 4xx for business rules (e.g. duplicate name → 409 with {detail: "name already exists"}).

Storage

• If the spec doesn't require persistence, use a top-level dict.
• If persistence is required, use stdlib sqlite3 (no SQLAlchemy dependency). Connection per-request via Depends.

Tests

• from fastapi.testclient import TestClient.
• Happy path: create, list, get, update, delete — assert each status code + each response body field.
• Error paths: 404 on missing id, 422 on bad input, 409 on duplicate (if applicable).
• Use pytest fixtures for the client + reset state between tests.

Anti-patterns

• DON'T use SQLAlchemy unless the user asks for it.
• DON'T return raw model instances — always go through a response_model so the OpenAPI schema is correct.
• DON'T print() in handlers — use logging (FastAPI sets up the root logger).
• DON'T forget from __future__ import annotations if you use forward type refs.

Source: devloper-gazi/Amor-Distributed-Artificial-Intelligence-System — distributed by TomeVault.