[web2py] writable=False cause error with primary key

[Omi Chiba]

Tested with MSSQL 2008 and DB2

If you connect existing table with primarykey and use writable=False
to any of the field on the form, it will show the following error.

Traceback (most recent call last):
  File "C:\web2py\gluon\restricted.py", line 194, in restricted
    exec ccode in environment
  File "C:/web2py/applications/otwitter/controllers/default.py", line
91, in <module>
  File "C:\web2py\gluon\globals.py", line 149, in <lambda>
    self._caller = lambda f: f()
  File "C:/web2py/applications/otwitter/controllers/default.py", line
33, in test
    if form.process().accepted:
  File "C:\web2py\gluon\html.py", line 1950, in process
    self.validate(**kwargs)
  File "C:\web2py\gluon\html.py", line 1898, in validate
    if self.accepts(**kwargs):
  File "C:\web2py\gluon\sqlhtml.py", line 1238, in accepts
    fields[field.name] = self.record[field.name]
TypeError: 'NoneType' object is not subscriptable


This is really critical for my project because I cannot use
writable=False to the fields I want to protect.


Table definition
--------------------------------
db.define_table('test',
    Field('mykey'),
    Field('field1'),
    Field('field2'),
    primarykey=['mykey'],
    migrate=False)

controller
---------------------------------
def test():
    db.test.field2.writable=False
    form = SQLFORM(db.test)
    if form.process().accepted:
        response.flash = 'form accepted'
    elif form.errors:
        response.flash = 'form has errors'
    return dict(form=form)

view
----------------------------------
{{extend 'layout.html'}}
<h1>test</h1>
{{=form}}