[QUESTION] List parameters in query string format

Description

Currently, only format with plain parameter name is supported when passing list of parameters https://fastapi.tiangolo.com/tutorial/query-params-str-validations/#query-parameter-list-multiple-values and only q=1&q=2&q=3 format is supported, however passing list parameters using indexed or not indexed square brackets is widely used across the web and web APIs. None of this is, unfortunately a standard defined in any RFC.

There are 3 most common ways of passing lists out there:

• q=1&q=2&q=3
• q[]=1&q[]=2&q[]=3
• q[0]=1&q[1]=2&q[2]=3

Some sdks, or clients for making requests by default send list using square brackets so there are some issues with configuration quite often.

Are there any plans to support square brackets for list parameters along with the current format?

[haynesgt]

This is what I ended up putting in my app:

@app.middleware("http")
async def fix_list_query_params(request: fastapi.Request, call_next):
    # Rails / some libs put square brackets on list parameters. FastAPI does not use the square brackets.
    def fix_key(key: str):
        if key and key.endswith("[]"):
            key = key[:-2]
        return key

    request._query_params = QueryParams(
        [(fix_key(key), value) for key, value in request.query_params.multi_items()]
    )
    request.scope["query_string"] = str(request.query_params)
    response = await call_next(request)
    return response

[haynesgt]

from fastapi.datastructures import QueryParams or from starlette.datastructures import QueryParams