FastAPI Query with dataclass not working with alias - python-3.x

Question

the following FastAPI code is producing unexpected behaviour to me:
import uvicorn
from fastapi import FastAPI, Depends, Query
from typing import Optional
from pydantic.dataclasses import dataclass
app = FastAPI()
#dataclass
class Catz:
qqq: Optional[str] = Query(None, alias="q")
#app.get("/productz/")
def search_products(query: Catz = Depends(Catz) ):
products = [{"name": "Computer"}, {"name": "HDD"}]
if not query.qqq:
query.qqq = ""
return {"query": query, "results": [product for product in products if query.qqq in product["name"]]}
#dataclass
class Cats:
qqq: Optional[str] = Query(None )
#app.get("/products/")
def search_products(query: Cats = Depends(Cats) ):
products = [{"name": "Computer"}, {"name": "HDD"}]
if not query.qqq:
query.qqq = ""
return {"query": query, "results": [product for product in products if query.qqq in product["name"]]}
if __name__ == "__main__":
uvicorn.run("main:app", port=11978, log_level="info", reload=True)
when I use the service via curl, I get the following outputs:
the expected behaviour with the endpoint /products/ that has no aliases
>> curl -X 'GET' 'http://localhost:11978/products/?qqq=H' -H 'accept: application/json' -H 'api-version: 1.0' ; echo
{"query":{"qqq":"H"},"results":[{"name":"HDD"}]}
not the expected behaviour with the endpoint /productz/ that has no aliases (regardless of me using a query parameter with its own name or with the alias I have in the code)
>> curl -X 'GET' 'http://localhost:11978/productz/?qqq=H' -H 'accept: application/json' -H 'api-version: 1.0' ; echo
{"query":{"qqq":""},"results":[{"name":"Computer"},{"name":"HDD"}]}
>> curl -X 'GET' 'http://localhost:11978/productz/?q=H' -H 'accept: application/json' -H 'api-version: 1.0' ; echo
{"query":{"qqq":""},"results":[{"name":"Computer"},{"name":"HDD"}]}
any idea why that would be?

Answer 1

Do not import dataclass from pydantic.dataclasses - it should be imported from Python's own built-in dataclasses module:
from fastapi import FastAPI, Depends, Query
from fastapi.exceptions import RequestValidationError
from dataclasses import dataclass
from typing import Optional
app = FastAPI()
#dataclass
class Catz:
qqq: Optional[str] = Query(None, alias="q")
#app.get("/productz/")
def search_products(query: Catz = Depends()):
products = [{"name": "Computer"}, {"name": "HDD"}]
if not query.qqq:
query.qqq = ""
return {"query": query, "results": [product for product in products if query]}
Outputs for /productz?q=123:
{"query":{"qqq":"123"},"results":[{"name":"Computer"},{"name":"HDD"}]}