[FEATURE] Query string flags

Is your feature request related to a problem? Please describe.

It is valid in HTML to have a query string parameter which has no value. For example: ?my-flag.

I usually think of this as a shorthand for writing ?my-flag=true.

FastAPI ignores these.

Describe the solution you’d like

FastAPI should not ignore these flags.

It could set their value to be:

• True.
• Empty string '' (I think this is bad idea - in intent these are usually for turning features on/off).
• Some constant like FastAPI.params.EmptyFlag.

Alternatively, you could make some special type which marks a query string parameter as present or not.

[GlennS]

Thanks for the good advice. I will bear that in mind next time I make something with FastAPI.

[tiangolo]

Here’s the thing, what is now supported in Starlette is to have empty query param flags. So, they are in the request.query_params dict, but with a value of None, because actually nothing was provided.

So, you could extract them if you use the request directly and check if the query parameter exists and if it is None: https://fastapi.tiangolo.com/advanced/using-request-directly/

But it wouldn’t make sense to make them used by default and take them as True implicitly, as that would be inconsistent with all the other cases.

For example, all these would make q have a value False`:

http://example.com?q=false http://example.com?q=0 http://example.com?q="" http://example.com?q=

But if then suddenly this made q to have a value True:

http://example.com?q

That would probably be quite unexpected.

So, yes, you can implement it by using the request directly, but it wouldn’t make sense as a default in FastAPI.