Add get_first_or_create method for CIVs (#3602)

There can be multiple CIVs with the same interface and value/image/file
in the DB. Retrieve the first of those if that's the case rather than
throwing an error.

Closes #3594

app/grandchallenge/algorithms/models.py

@@ -666,21 +666,21 @@ def retrieve_existing_civs(*, civ_data):
                 continue
             elif civ.image:
                 try:
-                    civ = ComponentInterfaceValue.objects.filter(
+                    civs = ComponentInterfaceValue.objects.filter(
                         interface__slug=civ.interface_slug, image=civ.image
-                    ).get()
-                    existing_civs.append(civ)
+                    ).all()
+                    existing_civs.extend(civs)
                 except ObjectDoesNotExist:
                     continue
             elif civ.file_civ:
                 existing_civs.append(civ.file_civ)
             else:
                 # values can be of different types, including None and False
                 try:
-                    civ = ComponentInterfaceValue.objects.filter(
+                    civs = ComponentInterfaceValue.objects.filter(
                         interface__slug=civ.interface_slug, value=civ.value
-                    ).get()
-                    existing_civs.append(civ)
+                    ).all()
+                    existing_civs.extend(civs)
                 except ObjectDoesNotExist:
                     continue
 

app/grandchallenge/components/models.py

@@ -1171,6 +1171,15 @@ def component_interface_value_path(instance, filename):
     )
 
 
+class ComponentInterfaceValueManager(models.Manager):
+
+    def get_first_or_create(self, **kwargs):
+        try:
+            return self.get_or_create(**kwargs)
+        except MultipleObjectsReturned:
+            return self.filter(**kwargs).first(), False
+
+
 class ComponentInterfaceValue(models.Model):
     """Encapsulates the value of an interface at a certain point in the graph."""
 
@@ -1238,6 +1247,8 @@ class ComponentInterfaceValue(models.Model):
 
     _user_upload_validated = False
 
+    objects = ComponentInterfaceValueManager()
+
     @property
     def title(self):
         if self.value is not None:
@@ -2249,7 +2260,7 @@ def create_civ_for_value(
     ):
         current_value = current_civ.value if current_civ else None
 
-        civ, created = ComponentInterfaceValue.objects.get_or_create(
+        civ, created = ComponentInterfaceValue.objects.get_first_or_create(
             interface=ci, value=new_value
         )
 
@@ -2290,9 +2301,10 @@ def create_civ_for_image(  # noqa: C901
     ):
         current_image = current_civ.image if current_civ else None
         if image and current_image != image:
-            civ, created = ComponentInterfaceValue.objects.get_or_create(
+            civ, created = ComponentInterfaceValue.objects.get_first_or_create(
                 interface=ci, image=image
             )
+
             if created:
                 try:
                     civ.full_clean()

app/grandchallenge/components/tasks.py

@@ -1203,7 +1203,7 @@ def add_image_to_object(
         interface=interface, upload_session=upload_session
     )
 
-    civ, created = ComponentInterfaceValue.objects.get_or_create(
+    civ, created = ComponentInterfaceValue.objects.get_first_or_create(
         interface=interface, image=image
     )
 

app/tests/components_tests/test_models.py

@@ -6,7 +6,7 @@
 from unittest.mock import call
 
 import pytest
-from django.core.exceptions import ValidationError
+from django.core.exceptions import MultipleObjectsReturned, ValidationError
 from django.core.files.base import ContentFile
 from django.utils import timezone
 from panimg.models import MAXIMUM_SEGMENTS_LENGTH
@@ -1581,3 +1581,23 @@ def test_all_examples_present():
     assert set(INTERFACE_TYPE_JSON_EXAMPLES.keys()) == set(
         InterfaceKind.interface_type_json()
     )
+
+
+@pytest.mark.django_db
+def test_component_interface_value_manager():
+    ci = ComponentInterfaceFactory(kind=InterfaceKindChoices.STRING)
+    civ1, civ2 = ComponentInterfaceValueFactory.create_batch(
+        2, interface=ci, value="Foo"
+    )
+
+    with pytest.raises(MultipleObjectsReturned):
+        ComponentInterfaceValue.objects.get_or_create(
+            interface=ci, value="Foo"
+        )
+
+    civ, created = ComponentInterfaceValue.objects.get_first_or_create(
+        interface=ci, value="Foo"
+    )
+
+    assert civ == civ1
+    assert not created