Filter out duplicate Contributors in submissions admin

scipost/managers.py

@@ -28,6 +28,12 @@ class ContributorQuerySet(models.QuerySet):
         """Return all validated and vetted Contributors."""
         return self.filter(user__is_active=True, status=NORMAL_CONTRIBUTOR)
 
+    def nonduplicates(self):
+        """
+        Filter out duplicate Contributors.
+        """
+        return self.exclude(duplicate_of__isnull=False)
+
     def available(self):
         """Filter out the Contributors that have active unavailability periods."""
         today = timezone.now().date()

submissions/admin.py

@@ -25,13 +25,13 @@ admin.site.register(iThenticateReport)
 class SubmissionAdminForm(forms.ModelForm):
     authors = forms.ModelMultipleChoiceField(
         required=False,
-        queryset=Contributor.objects.order_by('user__last_name'))
+        queryset=Contributor.objects.nonduplicates().order_by('user__last_name'))
     authors_claims = forms.ModelMultipleChoiceField(
         required=False,
-        queryset=Contributor.objects.order_by('user__last_name'))
+        queryset=Contributor.objects.nonduplicates().order_by('user__last_name'))
     authors_false_claims = forms.ModelMultipleChoiceField(
         required=False,
-        queryset=Contributor.objects.order_by('user__last_name'))
+        queryset=Contributor.objects.nonduplicates().order_by('user__last_name'))
     is_resubmission_of = forms.ModelChoiceField(
         required=False,
         queryset=Submission.objects.order_by('-preprint__identifier_w_vn_nr'))