RedirectView(query_string=True) produces double '?' when both destination URL and request have query parameters

[Ethan Jucovy]

When using the generic RedirectView(query_string=True) with a query string in the destination URL, the view always appends query string parameters from the incoming request with a ? separator. It should use & if there's also an existing query string in the incoming URL.

Currently, requests that come in with a query string end up redirected to a URL containing two question marks, e.g.:

path("redirect-me/", RedirectView.as_view(url="/destination/?pork=spam", query_string=True))

GET /redirect-me/?utm_source=foo

Currently results in:

Location: /destination/?pork=spam?utm_source=foo

Expected:

Location: /destination/?pork=spam&utm_source=foo

[Ethan Jucovy]

PR: ​https://github.com/django/django/pull/19610

[Natalia Bidart]

Hello Ethan Jucovy, thank you for taking the time to create this ticket and the PR. I think your report makes sense, I would also expect ? and & to be properly handled. Having said that, the current url manipulation logic feels somehow brittle and I wonder if we should consider a more robust implementation using urlparse. Have your given this some thought?

[Samriddha Kumar Tripathi]

Hi everyone, I see this ticket is still open and marked 'easy pickings'. Following Natalia's suggestion, I'd like to work on a new patch that uses urllib.parse for a more robust solution. Please let me know if it's okay for me to take this on

[Samriddha Kumar Tripathi]

Proposed fix in PR: ​https://github.com/django/django/pull/19833

[Sarah Boyce <42296566+sarahboyce@…>]

In a36df68:

Fixed #36488 -- Fixed merging of query strings in RedirectView.

Co-authored-by: Ethan Jucovy <ethan.jucovy@…>
Co-authored-by: Natalia <124304+nessita@…>

[Sarah Boyce <42296566+sarahboyce@…>]

In 359c1c6:

[6.0.x] Fixed #36488 -- Fixed merging of query strings in RedirectView.

Co-authored-by: Ethan Jucovy <ethan.jucovy@…>
Co-authored-by: Natalia <124304+nessita@…>

Backport of a36df6890d8995480f2e95ba556b77cef975d4f6 from main.