[MODPYTHON-256] util.FieldStorage __setitem__/__delitem__ might affect wrong field

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 3.3.1
• Component/s: core
• Environment: Any
• Assignee: Unassigned
• Reporter: Anders Blomdell
• Created: 02/Mar/10 08:23
• Updated: 02/Mar/10 08:28

Description

When a FieldStorage has two (or more) Filed instances with the same value but
different names, the behaviour of programs like this is (more or less) undefined:

fs = util.FieldStorage(req)
fs['id1'] = 'New value'
del fs['id2']

The reason for the undefinedness, is this code in _delitem_ (and the similar
in _setitem_):

table = self.list.table()
values = table[key]
for value in values:
self.list.remove(value)

What happens is that the self.list.remove(value) will remove the first field
with a matching value, regardless of that fields name. Here is an example from
real life:

form.clear()
form['id1'] = 'x'
form['id2'] = 'x'
form['id3'] = 'x'

1. Form now contains {'id2': [Field('id2', 'x')], # 'id3': [Field('id3', 'x')], # 'id1': [Field('id1', 'x')]}

   form['id2'] = 'y'

2. Form now contains {'id2': [Field('id2', 'x'), Field('id2', 'y')], # 'id3': [Field('id3', 'x')]}
3. which is not what I would have expected