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IObjectModifiedEvent always shows namedfile has changed #41

flipmcf opened this issue Nov 20, 2019 · 1 comment · Fixed by #42

IObjectModifiedEvent always shows namedfile has changed #41

flipmcf opened this issue Nov 20, 2019 · 1 comment · Fixed by #42


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@flipmcf flipmcf commented Nov 20, 2019

If I have a simple namedblobfile in my dexterity type:

class IVideo(model.Schema)
    video_file = NamedBlobFile(
        title=_('video file'),

Then register an event handler when a Video is modified:


And try to see if the video file was modified:

def modifyVideo(context, event)
    file_changed = False
    if hasattr(event, 'descriptions') and event.descriptions:
        for d in event.descriptions:
            if d.interface is IVideo and 'video_file' in d.attributes:
                file_changed = True

the field 'video_file' will always be present in the list.

When "Keep Existing File" is chosen in the widget, the widget should (??) set the new value to z3c.form.interfaces.NOT_CHANGED according to z3c.form.form 'applyChanges' function.

I'm not sure at all how to fix this myself. I hope I can get some help, if I analyzed the bug properly.

I don't see any documentation for the NOT_CHANGED interface flag - only code and a comment:

    # If the value is NOT_CHANGED, ignore it, since the widget/converter
    # sent a strong message not to do so.


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@flipmcf flipmcf commented Nov 20, 2019

I'm willing to work on this issue, if it is an issue, but at the time of this writing I have zero experience in widgets. Help would be appreciated

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