Tests and documentation about passing data and files to browser._request() via kwargs arg

[MartinDlry]

The function _request(self, form, url=None, **kwargs) from the Browser class retrieves data and files from kwargs argument :

data = kwargs.pop("data", dict())
files = kwargs.pop("files", dict())

However, this way of submitting data or files is not tested nor documented.

[MartinDlry]

I tried writing tests for this, but I've found a new issue.

After retrieving fields from kwargs["data"], the function processes fields inside form argument.
But, when processing these fields, it does not check if they were already filled with kwargs["data"], and the final request contains more than one value for the field. This could be considered as a normal behavior, except when the concerned fields are empty in the form argument.

For example, with a text input field named "test" , if we leave it empty, then call browser._request(data={"test": "mytext"}) ,
the resulting request will contain both "" and "mytext" for "test"field value.

To avoid this we could choose that kwargs["data] is priority, and, for each key in kwargs["data"], we will ignore the the corresponding field value in the form argument.

Do i have to open a new issue for this ?