Merge pull request #49 from plone/frisi/fix-upload-on-validation-errors

bugfix: do not lose file-upload after validation error

news/46.bugfix

@@ -0,0 +1 @@
+Fix issue where already uploaded images were lost when file validation error occurs (https://github.com/plone/plone.formwidget.namedfile/issues/46)  [fRiSi]

plone/formwidget/namedfile/converter.py

@@ -27,7 +27,8 @@ def toWidgetValue(self, value):
 
     def toFieldValue(self, value):
         action = self.widget.request.get("%s.action" % self.widget.name, None)
-        if action == 'nochange':
+        file_upload_id = self.widget.request.get("%s.file_upload_id" % self.widget.name, None) or 0
+        if action == 'nochange' and not file_upload_id:
             return NOT_CHANGED
 
         if value is None or value == '':

plone/formwidget/namedfile/widget.rst

@@ -543,6 +543,20 @@ and the converter will always set the value to z3c.form.interfaces.NOT_CHANGED::
   >>> image_converter.toFieldValue(u'') is NOT_CHANGED
   True
 
+On validation errors, file uploads are stored in a temporary storage. The id of the temporarily stored file is given
+by file_upload_id and action is set to 'nochange'.
+The widget returns the temporary file on `extract` as Named[Blob](File|Image) and the dataconverter will simply use it
+
+    >>> file_widget.request.form['widget.name.file.action'] = 'nochange'
+    >>> file_widget.request.form['widget.name.file.file_upload_id'] = '5c6cc90ce82941919daaeb62700e079a'
+    >>> file_converter.toFieldValue(NamedFile(data=b'testfile', filename=u'test.txt'))
+    <plone.namedfile.file.NamedFile object at ...>
+
+    >>> image_widget.request.form['widget.name.file.action'] = 'nochange'
+    >>> image_widget.request.form['widget.name.file.file_upload_id'] = '5c6cc90ce82941919daaeb62700e079a'
+    >>> file_converter.toFieldValue(NamedImage(data=b'testimage', filename=u'test.jpg'))
+    <plone.namedfile.file.NamedImage object at ...>
+
 
 The Base64Converter for Bytes fields
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