FormRequest.formdata with GET method duplicates same key in query string

[skynetbinary]

>>> from scrapy import FormRequest
>>> FormRequest('http://example.com/?id=9', method='GET', formdata={'id': '8'}).url
'http://example.com/?id=9&id=8'

Notice how id is being duplicated in query string. It must replace the value if same key is found. I believe this can be handled in form.py#L36.

[kmike]

Yes, this looks like a bug.

[jslay88]

Hopefully that works for you. First time making a PR, so please excuse any errors.

I would like some advice on how to build a good unit test for this, as I will admit, my testing experience is not great.

[keremgocen]

anyone working on this?

[Gallaecio]

I’m not sure this should be considered a bug. Specially after giving some thought to #4730.

Maybe we should simply raise a ValueError exception in this scenario, where formdata needs to be defined as a URL query string and the specified URL already has a query string.

[Gallaecio]

Fixed by #3579