On Jun 27, 2007, at 2:49 AM, Christian Zagrodnick wrote:

On 2007-06-26 22:41:25 +0200, Gary Poster <[EMAIL PROTECTED]> said:

On Jun 23, 2007, at 6:38 AM, Christian Zagrodnick wrote:
Log message for revision 76975:
FileWidget tries to be smarter about not deleting the currently stored content when the user did not upload a new file.
Modified: zope.app.form/trunk/src/zope/app/form/browser/ textwidgets.py
--- zope.app.form/trunk/src/zope/app/form/browser/textwidgets.py 2007-06-23 10:25:23 UTC (rev 76974) +++ zope.app.form/trunk/src/zope/app/form/browser/textwidgets.py 2007-06-23 10:38:37 UTC (rev 76975)
@@ -475,6 +475,11 @@
     def _toFieldValue(self, input):
         if input is None or input == '':
+ # There was no input. With File-Upload this usually means that the + # value should *not* change. Let's try to get the old value.
+            content = self.context.context
+            if self.context.interface.providedBy(content):
+                return self.context.get(content)
             return self.context.missing_value
             seek = input.seek
Hey. This has a couple of bugs, IMO. It might also be a misfeature, but I'm less sure about that. First, "return self.context.get(content)" assumes that this widget will be used on an edit form (not true for us). Second, "if self.context.interface.providedBy(content):" assumes that the schema field is part of an interface (not true for us).

Hum. From that I make that there are not enough tests. :/

Heh, yeah.

I suspect z3c.form is the way forward for us eventually. One never has enough tests, and 100% line coverage is only one way to count things, but the z3c.form story seems improved in many ways, importantly including its testing story.

I figure that the .interface attribute doesn't seem to be part of any interface anyway. So in fact this is not a nice thing to do.


Neither of these are valid assumptions generally for a form field, IMO. I'm also not sure about the semantics. Shouldn't this be handled more at the form level? I can see why you want to do this here, but it seems pretty gray, and I'm not sure how to solve the bugs in a sane and reliable way.

No, thinking about it it's not the right way I did it. Basically I wasn't aware about the different conexts. In general I know that, but sometimes you're just blind :)

I relate.

I agree that this is a tricky problem, and it would be nice to solve it, but your solution is not correct for a generic form widget. The only suggestion I have ATM is to revert this, unfortunately, but I welcome other approaches that solve the issues I raised.

Solving it on form level is of course possible but not really the thing you want to think about.

Right, I definitely understood your goal.

I suspect there should be some 'i have not changed' marker value.

There is some strange thing in zope.formlib.form.applyChanges preventing updates of the value already:

def applyChanges(context, form_fields, data, adapters=None):
   for form_field in form_fields:
       name = form_field.__name__
newvalue = data.get(name, form_field) # using form_field as marker if (newvalue is not form_field) and (field.get(adapter) != newvalue):
           changed = True
           field.set(adapter, newvalue)

   return changed

newvalue is not formfield? To me this does not make much sense. Why would I return self.context to indicate the value has not changed?

As the comment says, looks like form_field is being used as a marker--.get should (hopefully) never return form_field, which is precisely the point: that way, if get returns form_field, that means that there is not a new value of any sort.

Anyway, to the original problem. As I said, I don't know what to do except suggest that you revert here. Are you willing and able?

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