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https://github.com/Kludex/flake8-fastapi
Flake8 FastAPI - Avoid simple FastAPI mistakes ~opinionated~ 🤓
https://github.com/Kludex/flake8-fastapi
asgi fastapi flake8 python
Last synced: about 2 months ago
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Flake8 FastAPI - Avoid simple FastAPI mistakes ~opinionated~ 🤓
- Host: GitHub
- URL: https://github.com/Kludex/flake8-fastapi
- Owner: Kludex
- License: mit
- Created: 2021-06-01T08:07:52.000Z (about 3 years ago)
- Default Branch: main
- Last Pushed: 2023-01-29T09:52:34.000Z (over 1 year ago)
- Last Synced: 2024-05-07T01:02:59.600Z (about 2 months ago)
- Topics: asgi, fastapi, flake8, python
- Language: Python
- Homepage:
- Size: 81.1 KB
- Stars: 43
- Watchers: 2
- Forks: 4
- Open Issues: 3
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE
Lists
- awesome-flake8-extensions - flake8-fastapi - Checks FastAPI code against opinionated style rules. (Library-specific checks)
README
flake8-fastapi
A [flake8](https://flake8.pycqa.org/en/latest/index.html) plugin that helps you avoid simple FastAPI mistakes.
## Installation
First, install the package:
``` bash
pip install flake8-fastapi
```
Then, check if the plugin is installed using `flake8`:
``` bash
$ flake8 --version
6.0.0 (flake8-fastapi: 0.7.0, mccabe: 0.7.0, pycodestyle: 2.10.0, pyflakes: 3.0.1) CPython 3.8.11 on Linux
```
## Rules
- [CF001 - Route Decorator Error](#cf001---route-decorator-error)
- [CF002 - Router Prefix Error](#cf002---router-prefix-error)
- [CF008 - CORSMiddleware Order](#cf008---corsmiddleware-order)
- [CF009 - Undocumented HTTPException](#cf009---undocumented-httpexception)
- [CF011 - No Content Response](#cf011---no-content-response)
### CF001 - Route Decorator Error
Developers that were used to [flask](https://flask.palletsprojects.com/en/2.0.x/) can be persuaded or want to use the same pattern in FastAPI:
```python
from fastapi import FastAPI
app = FastAPI()
@app.route("/", methods=["GET"])
def home():
return "Hello world!"
```
But on FastAPI, we have a simpler way to define this (and is the most known way to create endpoints):
```python
from fastapi import FastAPI
app = FastAPI()
@app.get("/")
def home():
return "Hello world!"
```
### CF002 - Router Prefix Error
On old FastAPI versions, we were able to add a prefix only on the `include_router` method:
```python
from fastapi import APIRouter, FastAPI
router = APIRouter()
@router.get("/")
def home():
...
app = FastAPI()
app.include_router(router, prefix="/prefix")
```
Now, it's possible to add in the `Router` initialization:
```python
from fastapi import APIRouter, FastAPI
router = APIRouter(prefix="/prefix")
@router.get("/")
def home():
...
app = FastAPI()
app.include_router(router)
```
### CF008 - CORSMiddleware Order
There's a [tricky issue](https://github.com/tiangolo/fastapi/issues/1663) about [CORSMiddleware](https://www.starlette.io/middleware/#corsmiddleware) that people are usually unaware. Which is that this middleware should be the last one on the middleware stack. You can read more about it [here](https://github.com/tiangolo/fastapi/issues/1663).
Let's see an example of what doesn't work:
```python
from fastapi import FastAPI
app = FastAPI()
app.add_middleware(
CORSMiddleware,
allow_origins=['*'],
allow_credentials=True,
allow_methods=['*'],
allow_headers=['*']
)
app.add_middleware(GZipMiddleware)
```
As you see, the last middleware added is not `CORSMiddleware`, so it will not work as expected. On the other hand, if you change the order, it will:
```python
from fastapi import FastAPI
app = FastAPI()
app.add_middleware(GZipMiddleware)
app.add_middleware(
CORSMiddleware,
allow_origins=['*'],
allow_credentials=True,
allow_methods=['*'],
allow_headers=['*']
)
```
### CF009 - Undocumented HTTPException
Currently, there's no automatic solution to document the `HTTPException`s, besides the experimental package [`fastapi-responses`](https://github.com/Kludex/fastapi-responses).
For that reason, it's easy to forget the documentation, and have a lot of undocumented endpoints. Let's see an example:
```python
from fastapi import FastAPI, HTTPException
app = FastAPI()
@app.get("/")
def home():
raise HTTPException(status_code=400, detail="Bad Request")
```
The above endpoint doesn't have a `responses` field, even if it's clear that the response will have a `400` status code.
### CF011 - No Content Response
Currently, if you try to send a response with no content (204), FastAPI will send a 204 status with a non-empty body.
It will send a body content-length being 4 bytes.
You can verify this statement running the following code:
```python
# main.py
from fastapi import FastAPI
app = FastAPI()
@app.get("/", status_code=204)
def home():
...
```
Now feel free to run with your favorite server implementation:
```bash
uvicorn main:app
```
Then use curl or any other tool to send a request:
```bash
$ curl localhost:8000
* Trying 127.0.0.1:8000...
* TCP_NODELAY set
* Connected to localhost (127.0.0.1) port 8000 (#0)
> GET / HTTP/1.1
> Host: localhost:8000
> User-Agent: curl/7.68.0
> Accept: */*
>
* Mark bundle as not supporting multiuse
< HTTP/1.1 204 No Content
< date: Sat, 24 Jul 2021 19:21:24 GMT
< server: uvicorn
< content-length: 4
< content-type: application/json
<
* Connection #0 to host localhost left intact
```
This goes against the [RFC](https://tools.ietf.org/html/rfc7231#section-6.3.5), which specifies that a 204 response should have no body.
## License
This project is licensed under the terms of the MIT license.