newforms-admin: Fixed #6964 -- Implemented FileInput._has_changed. Before it was comparing the wrong values and causing it to trip up.

git-svn-id: http://code.djangoproject.com/svn/django/branches/newforms-admin@7506 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/newforms/widgets.py

@@ -262,6 +262,11 @@ class FileInput(Input):
     def value_from_datadict(self, data, files, name):
         "File widgets take data from FILES, not POST"
         return files.get(name, None)
+    
+    def _has_changed(self, initial, data):
+        if data is None:
+            return False
+        return True
 
 class Textarea(Widget):
     def __init__(self, attrs=None):

tests/regressiontests/forms/widgets.py

@@ -202,6 +202,30 @@ u'<input type="file" class="fun" name="email" />'
 >>> w.render('email', 'ŠĐĆŽćžšđ', attrs={'class': 'fun'})
 u'<input type="file" class="fun" name="email" />'
 
+Test for the behavior of _has_changed for FileInput. The value of data will
+more than likely come from request.FILES. The value of initial data will
+likely be a filename stored in the database. Since its value is of no use to
+a FileInput it is ignored.
+
+>>> w = FileInput()
+
+# No file was uploaded and no initial data.
+>>> w._has_changed(u'', None)
+False
+
+# A file was uploaded and no initial data.
+>>> w._has_changed(u'', {'filename': 'resume.txt', 'content': 'My resume'})
+True
+
+# A file was not uploaded, but there is initial data
+>>> w._has_changed(u'resume.txt', None)
+False
+
+# A file was uploaded and there is initial data (file identity is not dealt
+# with here)
+>>> w._has_changed('resume.txt', {'filename': 'resume.txt', 'content': 'My resume'})
+True
+
 # Textarea Widget #############################################################
 
 >>> w = Textarea()