On Aug 29, 2005, at 4:24 PM, Garrett Smith wrote:
To ease our own development, I forked the schema and widgets code a
while back. I don't think we've deviated too severely, but I've
added whatever 2 cents based on my experience below.
1 Flesh out the 'source' design and implementation so it can replace
and deprecate vocabularies. Specifically, to match the capabilities
of vocabularies, we'll add an interface that a source can implement
if they want to be bound to a context; and we will make it possible
to have iterable sources (for small collections as would be
appropriate for selections, radio button groups, checkbox groups,
etc.). This will reduce the potential for confusion by letting
sources be the 'one true way' to describe possible options for a
choice, instead of the current overlap of vocabularies and sources.
The primary advantage to sources over vocabularies are that
is cleaner; the only additional feature is the ability to configure
different tokens for a given source.
This sounds good. The one main hassle I've faced with vocabularies
is the seeming complexity of the queriables UI scheme. I've spent
much time tracking down how everything fits together, but
unfortunately never spent the time to figure out a simpler
approach. If it's already as simple as possible, fine -- sometimes
stuff's just hard to simplify.
It isn't the easiest thing to grok, no. We don't have any ideas to
improve it either, except to add more documentation, which is still
lacking AFAIK. Maybe writing more documentation will reveal other
2 Clean up the exceptions widget framework. The use of the widget
input error is quite messy: see collector issue 273. The idea would
be to make the use of the errors argument more consistent and more
restricted, and make the 'doc' implementation simpler.
I have a ValidationError that looks like this:
def __init__(self, msg, *args):
self.msg = msg
This was to workaround the strangeness of displaying a class-level
description, rather than the specific msg provided with the error.
Cool: yes, that's very, very similar to our internal one, except I
have an optional mapping arg (for values to be placed in the
i18n.Message) and no *args.
3 Make the arbitrary constraints in the schema framework more
powerful: specifically, allow a field to accept more than one
constraint, and have the constraints raise errors (with an i18n doc,
if desired) rather than return an uninformative Boolean.
This can be
done in a backwards (and deprecation) compatible way by keeping the
constraint argument and adding a constraints argument wit the new
semantics; or with another approach. *would need small proposal*
4 Recognize and document that the 'default' field argument is
actually 'initial value'. That is, if you set a field with a
to the missing_value, the default does not become the field's value:
the 'default' value is only used if the value has never been set
(i.e., during creation or when there is no previous state of the
value). Possibly rename to 'initial_value' (with deprecation
support). *would need proposal*
Our version of IField has an 'initial' attribute. We don't use
default. I prefer 'initial' to 'initial_value'.
That sounds good to me. I don't feel strongly about "initial_value":
short is good.
5 Allow fields to accept a default (or initial_value, as above) *or*
a default_getter (or initial_value_getter, as above).
initial_value_getter would be a callable passed the field's
It should return the desired initial value. Use cases include
initializing to now, today, the current user, etc. *would
proposal* *code exists*
Couldn't 'initial_getter' just be implemented using a property
version of 'initial'?
Yes, it could. The only downside is that it wouldn't be usable as an
initialization argument. I don't feel very strongly about it one way
or the other. It sounds like Jim is a definite -1 (as I thought he
might be :-) so I'm happy to drop it.
6 Add union field and widget to schema and form, respectively. A
union field allows a user to fill in one of several types of
Use cases include faux combo boxes (i.e., a choice or a text line),
date/duration choices, etc. Widget is reasonable and has been used
by ZC for more than a year. *would need small proposal* *code
7 add combination field and widget to schema and form,
A combination field allows a user to fill in multiple values
simultaneously, and returns a tuple of the combined values. Use
cases overlap somewhat with object field/widget, but this is simpler
to use for simple use cases. Use cases include range fields.
need small proposal* *code exists*
Cool. I don't know if this is the same thing, but we have a widget
that handles editing two related fields. One field is a boolean
that, when False, renders the other field not-applicable. E.g. when
the user unselects a checkbox, a list box becomes disabled. Our
implementation is a bit of a hack, since the widget has to cheat
and get access to additional fields.
Huh, interesting. It sounds different. What is the typical use for
this sort of field?
8 Add suggestion and MRU (Most Recently Used) widgets. These
provide a drop down of suggested (specifically most recently
the MRU widget) values for a choice field. They really make using
choice widgets much nicer in many cases. *code exists* *proposal
needed for also adding another of our packages to the core, on which
9 Add standard timezone source and widget. *code exists* for
something that should really be a shared community effort.
suggestion widget and MRU widget, above.
This would be super to have, consdering the proliferation of tzinfos.
10 The big restructuring of schema: divide up schema into interface
values and usage relationships. This is too big to explain in this
email, and probably too big to even adequately begin in two days.
This is the direction Jim wants to take schema, though, and I'm +1.
11 Brainstorm current state of the widget API and base classes and
start some significant cleanup of the zope/app/form/browser code.
Jim has been complaining vociferously about SimpleInputWidget. It's
probably time to nuke it (fine, deprecrete) and replace it with
helper functions ala utility.py.
There's quite a bit on the plate here. I'd be inclined to flesh out
in more detail the infrastructural pieces (vocab -> source,
constraints, widget API refactor) and leave new fields and widgets
That does make sense (though I'd love to finally get those fields and
widgets out the door). I don't expect the vocab or constraints stuff
to take too much time, actually, unless there is disagreement, but
plans for the widget API might be good to use focused "face time" on.
I can probably free up some time to look at SimpleInputWidget.
That would be great--you mean, during the same time as the sprint, or
before, or after? If before or during, we should probably coordinate.
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