<!--
Thank you for contributing to Ruff/ty! To help us out with reviewing,
please consider the following:
- Does this pull request include a summary of the change? (See below.)
- Does this pull request include a descriptive title? (Please prefix
with `[ty]` for ty pull
requests.)
- Does this pull request include references to any relevant issues?
-->
## Summary
Closes#17226.
This PR updates the `FAST003` rule to correctly handle [FastAPI class
dependencies](https://fastapi.tiangolo.com/tutorial/dependencies/classes-as-dependencies/).
Specifically, if a path parameter is declared in either:
- a `pydantic.BaseModel` used as a dependency, or
- the `__init__` method of a class used as a dependency,
then `FAST003` will no longer incorrectly report it as unused.
FastAPI allows a shortcut when using annotated class dependencies -
`Depends` can be called without arguments, e.g.:
```python
class MyParams(BaseModel):
my_id: int
@router.get("/{my_id}")
def get_id(params: Annotated[MyParams, Depends()]): ...
```
This PR ensures that such usage is properly supported by the linter.
Note: Support for dataclasses is not included in this PR. Let me know if
you’d like it to be added.
## Test Plan
Added relevant test cases to the `FAST003.py` fixture.
## Summary
The initial purpose was to fix#15043, where code like this:
```python
from fastapi import FastAPI, Query
app = FastAPI()
@app.get("/test")
def handler(echo: str = Query("")):
return echo
```
was being fixed to the invalid code below:
```python
from typing import Annotated
from fastapi import FastAPI, Query
app = FastAPI()
@app.get("/test")
def handler(echo: Annotated[str, Query("")]): # changed
return echo
```
As @MichaReiser pointed out, the correct fix is:
```python
from typing import Annotated
from fastapi import FastAPI, Query
app = FastAPI()
@app.get("/test")
def handler(echo: Annotated[str, Query()] = ""): # changed
return echo
```
After fixing the issue for `Query`, I realized that other classes like
`Path`, `Body`, `Cookie`, `Header`, `File`, and `Form` also looked
susceptible to this issue. The last few commits should handle these too,
which I think means this will also close#12913.
I had to reorder the arguments to the `do_stuff` test case because the
new fix removes some default argument values (eg for `Path`:
`some_path_param: str = Path()` becomes `some_path_param: Annotated[str,
Path()]`).
There's also #14484 related to this rule. I'm happy to take a stab at
that here or in a follow up PR too.
## Test Plan
`cargo test`
I also checked the fixed output with `uv run --with fastapi
FAST002_0.py`, but it required making a bunch of additional changes to
the test file that I wasn't sure we wanted in this PR.
---------
Co-authored-by: Micha Reiser <micha@reiser.io>
This adds the `fast-api-unused-path-parameter` lint rule, as described
in #12632.
I'm still pretty new to rust, so the code can probably be improved, feel
free to tell me if there's any changes i should make.
Also, i needed to add the `add_parameter` edit function, not sure if it
was in the scope of the PR or if i should've made another one.
