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From beagle-python
Reviews FastAPI code for routing patterns, dependency injection, validation, and async handlers. Use when reviewing FastAPI apps, checking APIRouter setup, Depends() usage, or response models.
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| Issue Type | Reference |
Guides FastAPI app development with Pydantic models, dependency injection, async DB access via SQLAlchemy/asyncpg, background tasks, WebSockets, and testing. Activates on FastAPI, Pydantic, or async Python API queries.
Builds FastAPI applications using async patterns, Pydantic models, dependency injection, route handlers, services, and repositories. For modern Python REST APIs.
Provides FastAPI patterns for async web APIs: lifespan events, Pydantic models, path/query parameters, dependency injection. Triggers on FastAPI keywords.
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| Issue Type | Reference |
|---|---|
| APIRouter setup, response_model, status codes | references/routes.md |
| Depends(), yield deps, cleanup, shared deps | references/dependencies.md |
| Pydantic models, HTTPException, 422 handling | references/validation.md |
| Async handlers, blocking I/O, background tasks | references/async.md |
response_model for type safetyDepends() not manual callsasync defrequests, time.sleep, open())except in route handlersThese are idiomatic FastAPI patterns that may appear problematic but are correct:
Depends(), not passed as function argumentsresponse_model is setOnly flag issues when the context warrants it:
Depends() with an auth dependencyRun once per FastAPI-related finding, after you can anchor file:line for the handler (see review-verification-protocol) and before the finding text ships. If a step’s pass condition is not met, do not assert the finding as written—gather evidence, withdraw, downgrade severity, or rephrase as a question.
| Step | Action | Pass condition |
|---|---|---|
| 1a | Open the handler’s route decorator in the repo (not from memory). | file:line for @router.* / @app.* (or the site that registers this handler). |
| 1b | Record HTTP method, response_model=, and status_code= on that decorator (or note they are absent). | Snippet from that line or explicit absent with the same file:line. |
| Step | Action | Pass condition |
|---|---|---|
| 2a | Read the full handler body. | file:line range covering the body. |
| 2b | If claiming blocking I/O: name each blocking call (e.g. requests., open(, time.sleep, sync DB/ORM). | Each call has file:line, or withdraw the finding if none after the read. |
| Step | Action | Pass condition |
|---|---|---|
| 3a | List parameters: Depends / Annotated[..., Depends], Pydantic models, Body/Query/Path, Request/Response. | Names + mechanism tied to file:line on the signature. |
| 3b | If claiming missing auth: search the handler file (and its APIRouter module if separate) for Depends, Security, HTTPBearer, or project auth dependencies. | Citation to an existing hook, or search result: paths searched + N matches (zero is allowed). |
| 3c | If claiming missing validation: confirm the argument is not already a Pydantic model or constrained Query/Path/Body. | Type/source with file:line, or withdraw if validation already applies. |
FastAPI + Pydantic handle many concerns automatically:
Before flagging "missing" functionality, verify FastAPI isn't handling it.