The urljoin() implementation cuts off the last base URL
character if the URL to join starts with a semicolon.
Expected output is no cut off characters.

$ python2.6
Python 2.6.6 (r266:84292, Aug 29 2010, 12:36:23) 
[GCC 4.4.5 20100824 (prerelease)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import urlparse
>>> print urlparse.urljoin('http://localhost:8080/feedback', ';jsessionid=XXX')
http://localhost:8080/feedbac;jsessionid=XXX
>>> 

... same in Python 3.1.2:

$ python3.1
Python 3.1.2 (release31-maint, Aug 29 2010, 18:45:17) 
[GCC 4.4.5 20100824 (prerelease)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import urllib.parse
>>> urllib.parse.urljoin('http://localhost:8080/feedback', ';jsessionid=XXX')
'http://localhost:8080/feedbac;jsessionid=XXX'
>>>

... in Python 2.5 the last path segment is cut off.
$ python2.5
Python 2.5.5 (r255:77872, Aug 23 2010, 02:55:15) 
[GCC 4.4.5 20100816 (prerelease)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
m>>> import urlparse
>>> print urlparse.urljoin('http://localhost:8080/feedback', ';jsessionid=XXX')
http://localhost:8080/;jsessionid=XXX
>>>

Update: the python2.5 behaviour is the expected and what I think the correct output.

The problem was be here:

path = path[:-1] # This is not needed and cuts last character
return urlunparse((scheme, netloc, path,
                  params, query, fragment))

I sent a patch.

PS. Sorry if I`m doing something wrong but it is my first patch and activity in the Python project.

The versions getting bug fixes are 2.7, 3.1 (stable versions) and 3.2 (active). 2.6 is in security mode now.

Can someone write a test (as a standalone script or a diff against Lib/test/test_urlparse.py) and tell if 3.1 and 3.2 have the bug too?

More importantly, can someone quote the latest URI RFC about that? The semicolon is related to the mysterious param component IIRC.

Simply applying the patch would break the testsuite of urlparse ( test_RFC3986 case of urljoin for ';' starting joinurls). The expected behavior should be trim off all receding chars until a '/'  and then join the semi-colon starting url. 2.5 behavior is the correct one.

Here's a patch for 3.2 which fixes this problem I believe. There does exist a test case that should have produced an error, except that the last path segment in RFC3986_BASE is only one character long. Had it been more than one character long, RFC3986 checks would have failed.

Also in the supplied patch is a test to catch this specific bug.

New patch (urlparse-9721-3.2.patch) against 3.2 which fixes the erroneous test.

Patch against 2.7 (urlparse-9721-2.7.patch).

Fixed in r87329, r87330 and r87331. Thanks for the patch Wes, that was proper.