From f15f3aeaad1899aecfb6f8ce50528124c4046a4a Mon Sep 17 00:00:00 2001
From: Matthew Elwell <matthew.elwell@flagsmith.com>
Date: Tue, 21 May 2024 10:43:38 +0100
Subject: [PATCH 01/17] Add test

---
 .../versioning/test_unit_versioning_views.py  | 63 +++++++++++++++++++
 1 file changed, 63 insertions(+)

diff --git a/api/tests/unit/features/versioning/test_unit_versioning_views.py b/api/tests/unit/features/versioning/test_unit_versioning_views.py
index 76d7b471840c..3d95d66197f6 100644
--- a/api/tests/unit/features/versioning/test_unit_versioning_views.py
+++ b/api/tests/unit/features/versioning/test_unit_versioning_views.py
@@ -638,3 +638,66 @@ def test_disable_v2_versioning_returns_bad_request_if_not_using_v2_versioning(
 
     # Then
     assert response.status_code == status.HTTP_400_BAD_REQUEST
+
+
+def test_create_new_version_with_changes_in_single_request(
+    environment_v2_versioning: Environment,
+    feature: Feature,
+    segment: Segment,
+    admin_client_new: APIClient,
+) -> None:
+    # Given
+    url = reverse(
+        "api-v1:versioning:environment-feature-versions-list",
+        args=[environment_v2_versioning.id, feature.id],
+    )
+
+    data = {
+        "publish": True,
+        "feature_states_to_update": [
+            {
+                "feature_segment": None,
+                "enabled": True,
+                "feature_state_value": {"type": "unicode", "string_value": "updated!"},
+            }
+        ],
+        "feature_states_to_delete": [],  # TODO: test deleting a feature state
+        "feature_states_to_create": [
+            {
+                "feature_segment": {
+                    # TODO: priorities?
+                    "segment": segment.id,
+                },
+                "enabled": True,
+                "feature_state_value": {"type": "unicode", "string_value": "foo"},
+            }
+        ],
+    }
+
+    # When
+    response = admin_client_new.post(
+        url, data=json.dumps(data), content_type="application/json"
+    )
+
+    # Then
+    assert response.status_code == status.HTTP_201_CREATED
+
+    new_version_uuid = response.json()["uuid"]
+    new_version = EnvironmentFeatureVersion.objects.get(uuid=new_version_uuid)
+
+    assert new_version.feature_states.count() == 2
+
+    new_version_environment_fs = new_version.feature_states.filter(
+        feature_segment__isnull=True
+    ).get()
+    assert new_version_environment_fs.get_feature_state_value() == "updated!"
+    assert new_version_environment_fs.enabled is True
+
+    new_version_segment_fs = new_version.feature_states.filter(
+        feature_segment__segment=segment
+    ).get()
+    assert new_version_segment_fs.get_feature_state_value() == "foo"
+    assert new_version_segment_fs.enabled is True
+
+    assert new_version.published is True
+    assert new_version.is_live is True

From 0f669158792477797c481cc8aaa73873fc36e695 Mon Sep 17 00:00:00 2001
From: Matthew Elwell <matthew.elwell@flagsmith.com>
Date: Tue, 21 May 2024 12:21:02 +0100
Subject: [PATCH 02/17] Add logic to create and publish a version in a single
 request

---
 api/features/versioning/serializers.py        | 121 ++++++++++++++++++
 api/features/versioning/views.py              |   4 +-
 .../versioning/test_unit_versioning_views.py  |  17 ++-
 3 files changed, 137 insertions(+), 5 deletions(-)

diff --git a/api/features/versioning/serializers.py b/api/features/versioning/serializers.py
index 1b91b6047a69..ac7b27180b2a 100644
--- a/api/features/versioning/serializers.py
+++ b/api/features/versioning/serializers.py
@@ -40,6 +40,127 @@ class Meta:
         )
 
 
+class EnvironmentFeatureVersionCreateSerializer(EnvironmentFeatureVersionSerializer):
+    feature_states_to_create = EnvironmentFeatureVersionFeatureStateSerializer(
+        many=True, allow_null=True, required=False
+    )
+    feature_states_to_update = EnvironmentFeatureVersionFeatureStateSerializer(
+        many=True, allow_null=True, required=False
+    )
+    segment_ids_to_delete_overrides = serializers.ListSerializer(
+        child=serializers.IntegerField(),
+        required=False,
+        allow_null=True,
+    )
+    publish = serializers.BooleanField(required=False, default=False)
+
+    class Meta(EnvironmentFeatureVersionSerializer.Meta):
+        fields = EnvironmentFeatureVersionSerializer.Meta.fields + (
+            "feature_states_to_create",
+            "feature_states_to_update",
+            "segment_ids_to_delete_overrides",
+            "publish",
+        )
+        non_model_fields = (
+            "feature_states_to_create",
+            "feature_states_to_update",
+            "segment_ids_to_delete_overrides",
+            "publish",
+        )
+
+    def create(self, validated_data):
+        for field_name in self.Meta.non_model_fields:
+            validated_data.pop(field_name, None)
+
+        version = super().create(validated_data)
+
+        for feature_state_to_create in self.initial_data.get(
+            "feature_states_to_create", []
+        ):
+            self._create_feature_state(
+                {**feature_state_to_create, "environment": version.environment_id},
+                version,
+            )
+
+        for feature_state_to_update in self.initial_data.get(
+            "feature_states_to_update", []
+        ):
+            self._update_feature_state(feature_state_to_update, version)
+
+        self._delete_feature_states(
+            self.initial_data.get("segment_ids_to_delete_overrides", []), version
+        )
+
+        if self.initial_data.get("publish", False):
+            request = self.context["request"]
+            version.publish(
+                published_by=(
+                    request.user if isinstance(request.user, FFAdminUser) else None
+                )
+            )
+
+        return version
+
+    def _create_feature_state(
+        self, feature_state: dict, version: EnvironmentFeatureVersion
+    ) -> None:
+        if not self._is_segment_override(feature_state):
+            raise serializers.ValidationError(
+                "Cannot create FeatureState objects that are not segment overrides."
+            )
+
+        segment_id = feature_state["feature_segment"]["segment"]
+        if version.feature_states.filter(
+            feature_segment__segment_id=segment_id
+        ).exists():
+            raise serializers.ValidationError(
+                "Segment override already exists for Segment %d", segment_id
+            )
+
+        fs_serializer = EnvironmentFeatureVersionFeatureStateSerializer(
+            data=feature_state,
+            context={
+                "feature": version.feature,
+                "environment": version.environment,
+                "environment_feature_version": version,
+            },
+        )
+        fs_serializer.is_valid(raise_exception=True)
+        fs_serializer.save(
+            environment_feature_version=version,
+            environment=version.environment,
+            feature=version.feature,
+        )
+
+    def _update_feature_state(
+        self, feature_state: dict, version: EnvironmentFeatureVersion
+    ) -> None:
+        if self._is_segment_override(feature_state):
+            instance = version.feature_states.get(
+                feature_segment__segment_id=feature_state["feature_segment"]["segment"]
+            )
+        else:
+            instance = version.feature_states.get(feature_segment__isnull=True)
+
+        fs_serializer = EnvironmentFeatureVersionFeatureStateSerializer(
+            instance=instance, data=feature_state
+        )
+        fs_serializer.is_valid(raise_exception=True)
+        fs_serializer.save(
+            environment_feature_version=version, environment=version.environment
+        )
+
+    def _delete_feature_states(
+        self, segment_ids: list[int], version: EnvironmentFeatureVersion
+    ) -> None:
+        version.feature_states.filter(
+            feature_segment__segment_id__in=segment_ids
+        ).delete()
+
+    def _is_segment_override(self, feature_state: dict) -> bool:
+        return feature_state.get("feature_segment") is not None
+
+
 class EnvironmentFeatureVersionPublishSerializer(serializers.Serializer):
     live_from = serializers.DateTimeField(required=False)
 
diff --git a/api/features/versioning/views.py b/api/features/versioning/views.py
index 3275db292843..5f5de98d85a1 100644
--- a/api/features/versioning/views.py
+++ b/api/features/versioning/views.py
@@ -27,6 +27,7 @@
     EnvironmentFeatureVersionPermissions,
 )
 from features.versioning.serializers import (
+    EnvironmentFeatureVersionCreateSerializer,
     EnvironmentFeatureVersionFeatureStateSerializer,
     EnvironmentFeatureVersionPublishSerializer,
     EnvironmentFeatureVersionQuerySerializer,
@@ -48,7 +49,6 @@ class EnvironmentFeatureVersionViewSet(
     CreateModelMixin,
     DestroyModelMixin,
 ):
-    serializer_class = EnvironmentFeatureVersionSerializer
     permission_classes = [IsAuthenticated, EnvironmentFeatureVersionPermissions]
 
     def __init__(self, *args, **kwargs):
@@ -62,6 +62,8 @@ def get_serializer_class(self):
         match self.action:
             case "publish":
                 return EnvironmentFeatureVersionPublishSerializer
+            case "create":
+                return EnvironmentFeatureVersionCreateSerializer
             case _:
                 return EnvironmentFeatureVersionSerializer
 
diff --git a/api/tests/unit/features/versioning/test_unit_versioning_views.py b/api/tests/unit/features/versioning/test_unit_versioning_views.py
index 3d95d66197f6..74a13fcc490d 100644
--- a/api/tests/unit/features/versioning/test_unit_versioning_views.py
+++ b/api/tests/unit/features/versioning/test_unit_versioning_views.py
@@ -641,12 +641,17 @@ def test_disable_v2_versioning_returns_bad_request_if_not_using_v2_versioning(
 
 
 def test_create_new_version_with_changes_in_single_request(
-    environment_v2_versioning: Environment,
     feature: Feature,
     segment: Segment,
+    segment_featurestate: FeatureState,
     admin_client_new: APIClient,
+    environment_v2_versioning: Environment,
 ) -> None:
     # Given
+    another_segment = Segment.objects.create(
+        name="another-segment", project=feature.project
+    )
+
     url = reverse(
         "api-v1:versioning:environment-feature-versions-list",
         args=[environment_v2_versioning.id, feature.id],
@@ -661,17 +666,17 @@ def test_create_new_version_with_changes_in_single_request(
                 "feature_state_value": {"type": "unicode", "string_value": "updated!"},
             }
         ],
-        "feature_states_to_delete": [],  # TODO: test deleting a feature state
         "feature_states_to_create": [
             {
                 "feature_segment": {
                     # TODO: priorities?
-                    "segment": segment.id,
+                    "segment": another_segment.id,
                 },
                 "enabled": True,
                 "feature_state_value": {"type": "unicode", "string_value": "foo"},
             }
         ],
+        "segment_ids_to_delete_overrides": [segment.id],
     }
 
     # When
@@ -694,10 +699,14 @@ def test_create_new_version_with_changes_in_single_request(
     assert new_version_environment_fs.enabled is True
 
     new_version_segment_fs = new_version.feature_states.filter(
-        feature_segment__segment=segment
+        feature_segment__segment=another_segment
     ).get()
     assert new_version_segment_fs.get_feature_state_value() == "foo"
     assert new_version_segment_fs.enabled is True
 
+    assert not new_version.feature_states.filter(
+        feature_segment__segment=segment
+    ).exists()
+
     assert new_version.published is True
     assert new_version.is_live is True

From 9a3240cea67c4f6a5298270633c63a4270eb8f2e Mon Sep 17 00:00:00 2001
From: Matthew Elwell <matthew.elwell@flagsmith.com>
Date: Tue, 21 May 2024 12:30:02 +0100
Subject: [PATCH 03/17] Add help text to serializers

---
 api/features/versioning/serializers.py | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/api/features/versioning/serializers.py b/api/features/versioning/serializers.py
index ac7b27180b2a..918deb569899 100644
--- a/api/features/versioning/serializers.py
+++ b/api/features/versioning/serializers.py
@@ -42,17 +42,31 @@ class Meta:
 
 class EnvironmentFeatureVersionCreateSerializer(EnvironmentFeatureVersionSerializer):
     feature_states_to_create = EnvironmentFeatureVersionFeatureStateSerializer(
-        many=True, allow_null=True, required=False
+        many=True,
+        allow_null=True,
+        required=False,
+        help_text=(
+            "Array of feature states that will be created in the new version. "
+            "Note: these can only include segment overrides."
+        ),
     )
     feature_states_to_update = EnvironmentFeatureVersionFeatureStateSerializer(
-        many=True, allow_null=True, required=False
+        many=True,
+        allow_null=True,
+        required=False,
+        help_text="Array of feature states to update in the new version.",
     )
     segment_ids_to_delete_overrides = serializers.ListSerializer(
         child=serializers.IntegerField(),
         required=False,
         allow_null=True,
+        help_text="Array of segment ids for which the segment overrides will be removed in the new version.",
+    )
+    publish = serializers.BooleanField(
+        required=False,
+        default=False,
+        help_text="Boolean to confirm whether the new version should be publish immediately or not.",
     )
-    publish = serializers.BooleanField(required=False, default=False)
 
     class Meta(EnvironmentFeatureVersionSerializer.Meta):
         fields = EnvironmentFeatureVersionSerializer.Meta.fields + (

From 35a329b34f5cd00a2c2ab6885f10e39f0b1ea5ec Mon Sep 17 00:00:00 2001
From: Matthew Elwell <matthew.elwell@flagsmith.com>
Date: Thu, 23 May 2024 09:55:04 +0100
Subject: [PATCH 04/17] Update serializer attribute name to avoid odd DRF
 behaviour

---
 api/features/versioning/serializers.py                | 11 +++++++----
 .../features/versioning/test_unit_versioning_views.py |  2 +-
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/api/features/versioning/serializers.py b/api/features/versioning/serializers.py
index 918deb569899..b4adba78b599 100644
--- a/api/features/versioning/serializers.py
+++ b/api/features/versioning/serializers.py
@@ -62,7 +62,7 @@ class EnvironmentFeatureVersionCreateSerializer(EnvironmentFeatureVersionSeriali
         allow_null=True,
         help_text="Array of segment ids for which the segment overrides will be removed in the new version.",
     )
-    publish = serializers.BooleanField(
+    publish_immediately = serializers.BooleanField(
         required=False,
         default=False,
         help_text="Boolean to confirm whether the new version should be publish immediately or not.",
@@ -73,13 +73,13 @@ class Meta(EnvironmentFeatureVersionSerializer.Meta):
             "feature_states_to_create",
             "feature_states_to_update",
             "segment_ids_to_delete_overrides",
-            "publish",
+            "publish_immediately",
         )
         non_model_fields = (
             "feature_states_to_create",
             "feature_states_to_update",
             "segment_ids_to_delete_overrides",
-            "publish",
+            "publish_immediately",
         )
 
     def create(self, validated_data):
@@ -88,6 +88,9 @@ def create(self, validated_data):
 
         version = super().create(validated_data)
 
+        # Note that we use self.initial_data for handling the feature states here
+        # since we want the raw data to pass into the serializers in the separate
+        # private methods used for modifying the FeatureState objects.
         for feature_state_to_create in self.initial_data.get(
             "feature_states_to_create", []
         ):
@@ -105,7 +108,7 @@ def create(self, validated_data):
             self.initial_data.get("segment_ids_to_delete_overrides", []), version
         )
 
-        if self.initial_data.get("publish", False):
+        if self.validated_data.get("publish_immediately", False):
             request = self.context["request"]
             version.publish(
                 published_by=(
diff --git a/api/tests/unit/features/versioning/test_unit_versioning_views.py b/api/tests/unit/features/versioning/test_unit_versioning_views.py
index 74a13fcc490d..76ee9938a2a6 100644
--- a/api/tests/unit/features/versioning/test_unit_versioning_views.py
+++ b/api/tests/unit/features/versioning/test_unit_versioning_views.py
@@ -658,7 +658,7 @@ def test_create_new_version_with_changes_in_single_request(
     )
 
     data = {
-        "publish": True,
+        "publish_immediately": True,
         "feature_states_to_update": [
             {
                 "feature_segment": None,

From 41a0751f8dd14c8369d00cb91e66c054af804de1 Mon Sep 17 00:00:00 2001
From: Matthew Elwell <matthew.elwell@flagsmith.com>
Date: Thu, 23 May 2024 10:31:53 +0100
Subject: [PATCH 05/17] Handle segment overrides priority

---
 api/features/feature_segments/serializers.py  | 13 ++++-
 .../versioning/test_unit_versioning_views.py  | 52 ++++++++++++++-----
 2 files changed, 52 insertions(+), 13 deletions(-)

diff --git a/api/features/feature_segments/serializers.py b/api/features/feature_segments/serializers.py
index 519fe62a8c68..5a9c72181d42 100644
--- a/api/features/feature_segments/serializers.py
+++ b/api/features/feature_segments/serializers.py
@@ -37,10 +37,21 @@ def validate(self, data):
 
 
 class CreateSegmentOverrideFeatureSegmentSerializer(serializers.ModelSerializer):
+    priority = serializers.IntegerField(min_value=1, required=False)
+
     class Meta:
         model = FeatureSegment
         fields = ("id", "segment", "priority", "uuid")
-        read_only_fields = ("priority",)
+
+    def save(self, **kwargs):
+        priority: int | None = self.initial_data.pop("priority", None)
+
+        feature_segment: FeatureSegment = super().save(**kwargs)
+
+        if priority:
+            feature_segment.to(priority)
+
+        return feature_segment
 
 
 class FeatureSegmentQuerySerializer(serializers.Serializer):
diff --git a/api/tests/unit/features/versioning/test_unit_versioning_views.py b/api/tests/unit/features/versioning/test_unit_versioning_views.py
index 76ee9938a2a6..0787d3b41864 100644
--- a/api/tests/unit/features/versioning/test_unit_versioning_views.py
+++ b/api/tests/unit/features/versioning/test_unit_versioning_views.py
@@ -644,12 +644,18 @@ def test_create_new_version_with_changes_in_single_request(
     feature: Feature,
     segment: Segment,
     segment_featurestate: FeatureState,
-    admin_client_new: APIClient,
+    admin_client: APIClient,
     environment_v2_versioning: Environment,
 ) -> None:
+    # TODO: replace fixture with admin_client_new
+    admin_client_new = admin_client
+
     # Given
-    another_segment = Segment.objects.create(
-        name="another-segment", project=feature.project
+    additional_segment_1 = Segment.objects.create(
+        name="additional-segment-1", project=feature.project
+    )
+    additional_segment_2 = Segment.objects.create(
+        name="additional-segment-2", project=feature.project
     )
 
     url = reverse(
@@ -669,12 +675,26 @@ def test_create_new_version_with_changes_in_single_request(
         "feature_states_to_create": [
             {
                 "feature_segment": {
-                    # TODO: priorities?
-                    "segment": another_segment.id,
+                    "segment": additional_segment_1.id,
+                    "priority": 2,
                 },
                 "enabled": True,
-                "feature_state_value": {"type": "unicode", "string_value": "foo"},
-            }
+                "feature_state_value": {
+                    "type": "unicode",
+                    "string_value": "segment-override-1",
+                },
+            },
+            {
+                "feature_segment": {
+                    "segment": additional_segment_2.id,
+                    "priority": 1,
+                },
+                "enabled": True,
+                "feature_state_value": {
+                    "type": "unicode",
+                    "string_value": "segment-override-2",
+                },
+            },
         ],
         "segment_ids_to_delete_overrides": [segment.id],
     }
@@ -690,7 +710,7 @@ def test_create_new_version_with_changes_in_single_request(
     new_version_uuid = response.json()["uuid"]
     new_version = EnvironmentFeatureVersion.objects.get(uuid=new_version_uuid)
 
-    assert new_version.feature_states.count() == 2
+    assert new_version.feature_states.count() == 3
 
     new_version_environment_fs = new_version.feature_states.filter(
         feature_segment__isnull=True
@@ -698,11 +718,19 @@ def test_create_new_version_with_changes_in_single_request(
     assert new_version_environment_fs.get_feature_state_value() == "updated!"
     assert new_version_environment_fs.enabled is True
 
-    new_version_segment_fs = new_version.feature_states.filter(
-        feature_segment__segment=another_segment
+    new_version_segment_fs_1 = new_version.feature_states.filter(
+        feature_segment__segment=additional_segment_1
+    ).get()
+    assert new_version_segment_fs_1.get_feature_state_value() == "segment-override-1"
+    assert new_version_segment_fs_1.enabled is True
+    assert new_version_segment_fs_1.feature_segment.priority == 2
+
+    new_version_segment_fs_2 = new_version.feature_states.filter(
+        feature_segment__segment=additional_segment_2
     ).get()
-    assert new_version_segment_fs.get_feature_state_value() == "foo"
-    assert new_version_segment_fs.enabled is True
+    assert new_version_segment_fs_2.get_feature_state_value() == "segment-override-2"
+    assert new_version_segment_fs_2.enabled is True
+    assert new_version_segment_fs_2.feature_segment.priority == 1
 
     assert not new_version.feature_states.filter(
         feature_segment__segment=segment

From 095754036a91e740de23b5b933784874f518dc4a Mon Sep 17 00:00:00 2001
From: Matthew Elwell <matthew.elwell@flagsmith.com>
Date: Thu, 23 May 2024 10:33:09 +0100
Subject: [PATCH 06/17] Improve help text

---
 api/features/versioning/serializers.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/api/features/versioning/serializers.py b/api/features/versioning/serializers.py
index b4adba78b599..a266dfb6fbf3 100644
--- a/api/features/versioning/serializers.py
+++ b/api/features/versioning/serializers.py
@@ -60,7 +60,7 @@ class EnvironmentFeatureVersionCreateSerializer(EnvironmentFeatureVersionSeriali
         child=serializers.IntegerField(),
         required=False,
         allow_null=True,
-        help_text="Array of segment ids for which the segment overrides will be removed in the new version.",
+        help_text="List of segment ids for which the segment overrides will be removed in the new version.",
     )
     publish_immediately = serializers.BooleanField(
         required=False,

From a439242238bcc5bf5b3c59693384d89763e480ec Mon Sep 17 00:00:00 2001
From: Matthew Elwell <matthew.elwell@flagsmith.com>
Date: Thu, 23 May 2024 10:33:53 +0100
Subject: [PATCH 07/17] Re-add admin_client_new fixture

---
 .../unit/features/versioning/test_unit_versioning_views.py   | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/api/tests/unit/features/versioning/test_unit_versioning_views.py b/api/tests/unit/features/versioning/test_unit_versioning_views.py
index 0787d3b41864..0d67d4a638d9 100644
--- a/api/tests/unit/features/versioning/test_unit_versioning_views.py
+++ b/api/tests/unit/features/versioning/test_unit_versioning_views.py
@@ -644,12 +644,9 @@ def test_create_new_version_with_changes_in_single_request(
     feature: Feature,
     segment: Segment,
     segment_featurestate: FeatureState,
-    admin_client: APIClient,
+    admin_client_new: APIClient,
     environment_v2_versioning: Environment,
 ) -> None:
-    # TODO: replace fixture with admin_client_new
-    admin_client_new = admin_client
-
     # Given
     additional_segment_1 = Segment.objects.create(
         name="additional-segment-1", project=feature.project

From 0fd8ef3d3fab4c29ce37899694dd3fde4fed9ea3 Mon Sep 17 00:00:00 2001
From: Matthew Elwell <matthew.elwell@flagsmith.com>
Date: Thu, 23 May 2024 11:01:28 +0100
Subject: [PATCH 08/17] Add test for updating and creating segment overrides
 simultaneously

---
 api/features/versioning/serializers.py        | 11 ++-
 .../versioning/test_unit_versioning_views.py  | 79 +++++++++++++++++++
 2 files changed, 89 insertions(+), 1 deletion(-)

diff --git a/api/features/versioning/serializers.py b/api/features/versioning/serializers.py
index a266dfb6fbf3..bbc28e93c958 100644
--- a/api/features/versioning/serializers.py
+++ b/api/features/versioning/serializers.py
@@ -156,11 +156,20 @@ def _update_feature_state(
             instance = version.feature_states.get(
                 feature_segment__segment_id=feature_state["feature_segment"]["segment"]
             )
+            # Patch the id of the feature segment onto the feature state data so that
+            # the serializer knows to update rather than try and create a new one.
+            feature_state["feature_segment"]["id"] = instance.feature_segment_id
         else:
             instance = version.feature_states.get(feature_segment__isnull=True)
 
         fs_serializer = EnvironmentFeatureVersionFeatureStateSerializer(
-            instance=instance, data=feature_state
+            instance=instance,
+            data=feature_state,
+            context={
+                "feature": version.feature,
+                "environment": version.environment,
+                "environment_feature_version": version,
+            },
         )
         fs_serializer.is_valid(raise_exception=True)
         fs_serializer.save(
diff --git a/api/tests/unit/features/versioning/test_unit_versioning_views.py b/api/tests/unit/features/versioning/test_unit_versioning_views.py
index 0d67d4a638d9..b759322c64ea 100644
--- a/api/tests/unit/features/versioning/test_unit_versioning_views.py
+++ b/api/tests/unit/features/versioning/test_unit_versioning_views.py
@@ -735,3 +735,82 @@ def test_create_new_version_with_changes_in_single_request(
 
     assert new_version.published is True
     assert new_version.is_live is True
+
+
+def test_update_and_create_segment_override_in_single_request(
+    feature: Feature,
+    segment: Segment,
+    segment_featurestate: FeatureState,
+    admin_client: APIClient,
+    environment_v2_versioning: Environment,
+) -> None:
+    # Given
+    additional_segment = Segment.objects.create(
+        name="additional-segment", project=feature.project
+    )
+
+    url = reverse(
+        "api-v1:versioning:environment-feature-versions-list",
+        args=[environment_v2_versioning.id, feature.id],
+    )
+
+    data = {
+        "publish_immediately": True,
+        "feature_states_to_update": [
+            {
+                "feature_segment": {"segment": segment.id, "priority": 2},
+                "enabled": True,
+                "feature_state_value": {
+                    "type": "unicode",
+                    "string_value": "updated-segment-override",
+                },
+            }
+        ],
+        "feature_states_to_create": [
+            {
+                "feature_segment": {
+                    "segment": additional_segment.id,
+                    "priority": 1,
+                },
+                "enabled": True,
+                "feature_state_value": {
+                    "type": "unicode",
+                    "string_value": "additional-segment-override",
+                },
+            },
+        ],
+    }
+
+    # When
+    response = admin_client.post(
+        url, data=json.dumps(data), content_type="application/json"
+    )
+
+    # Then
+    assert response.status_code == status.HTTP_201_CREATED
+
+    new_version_uuid = response.json()["uuid"]
+    new_version = EnvironmentFeatureVersion.objects.get(uuid=new_version_uuid)
+
+    assert new_version.feature_states.count() == 3
+
+    updated_segment_override = new_version.feature_states.filter(
+        feature_segment__segment=segment
+    ).get()
+    assert (
+        updated_segment_override.get_feature_state_value() == "updated-segment-override"
+    )
+    assert updated_segment_override.enabled is True
+    assert updated_segment_override.feature_segment.priority == 2
+
+    new_segment_override = new_version.feature_states.filter(
+        feature_segment__segment=additional_segment
+    ).get()
+    assert (
+        new_segment_override.get_feature_state_value() == "additional-segment-override"
+    )
+    assert new_segment_override.enabled is True
+    assert new_segment_override.feature_segment.priority == 1
+
+    assert new_version.published is True
+    assert new_version.is_live is True

From 055a85e6f26442aa957064a98f865a3221e0456d Mon Sep 17 00:00:00 2001
From: Matthew Elwell <matthew.elwell@flagsmith.com>
Date: Thu, 23 May 2024 11:04:21 +0100
Subject: [PATCH 09/17] Add another comment

---
 api/features/feature_segments/serializers.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/api/features/feature_segments/serializers.py b/api/features/feature_segments/serializers.py
index 5a9c72181d42..541cfaf353fe 100644
--- a/api/features/feature_segments/serializers.py
+++ b/api/features/feature_segments/serializers.py
@@ -37,6 +37,9 @@ def validate(self, data):
 
 
 class CreateSegmentOverrideFeatureSegmentSerializer(serializers.ModelSerializer):
+    # Since the `priority` field on the FeatureSegment model is set to editable=False
+    # (to adhere to the django-ordered-model functionality), we redefine the priority
+    # field here, and use it manually in the save method.
     priority = serializers.IntegerField(min_value=1, required=False)
 
     class Meta:

From 26b4c8fa3c8a37955dad41f792492c356e34817b Mon Sep 17 00:00:00 2001
From: Matthew Elwell <matthew.elwell@flagsmith.com>
Date: Thu, 23 May 2024 11:05:18 +0100
Subject: [PATCH 10/17] Update comment

---
 api/features/versioning/serializers.py | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/api/features/versioning/serializers.py b/api/features/versioning/serializers.py
index bbc28e93c958..d3661b592ffe 100644
--- a/api/features/versioning/serializers.py
+++ b/api/features/versioning/serializers.py
@@ -89,8 +89,9 @@ def create(self, validated_data):
         version = super().create(validated_data)
 
         # Note that we use self.initial_data for handling the feature states here
-        # since we want the raw data to pass into the serializers in the separate
-        # private methods used for modifying the FeatureState objects.
+        # since we want the raw data (rather than the serialized ORM objects) to
+        # pass into the serializers in the separate private methods used for modifying
+        # the FeatureState objects.
         for feature_state_to_create in self.initial_data.get(
             "feature_states_to_create", []
         ):

From 640a9364983a9d1df5d6ba949a3f87a769402e77 Mon Sep 17 00:00:00 2001
From: Matthew Elwell <matthew.elwell@flagsmith.com>
Date: Thu, 23 May 2024 11:44:18 +0100
Subject: [PATCH 11/17] Increase coverage by testing failure paths

---
 api/features/versioning/serializers.py        |  9 ++-
 .../versioning/test_unit_versioning_views.py  | 76 +++++++++++++++++++
 2 files changed, 83 insertions(+), 2 deletions(-)

diff --git a/api/features/versioning/serializers.py b/api/features/versioning/serializers.py
index 186db3c7467d..af72834859c5 100644
--- a/api/features/versioning/serializers.py
+++ b/api/features/versioning/serializers.py
@@ -148,7 +148,9 @@ def _create_feature_state(
     ) -> None:
         if not self._is_segment_override(feature_state):
             raise serializers.ValidationError(
-                "Cannot create FeatureState objects that are not segment overrides."
+                {
+                    "feature_states_to_create": "Cannot create FeatureState objects that are not segment overrides."
+                }
             )
 
         segment_id = feature_state["feature_segment"]["segment"]
@@ -156,7 +158,10 @@ def _create_feature_state(
             feature_segment__segment_id=segment_id
         ).exists():
             raise serializers.ValidationError(
-                "Segment override already exists for Segment %d", segment_id
+                {
+                    "feature_states_to_create": "Segment override already exists for Segment %d"
+                    % segment_id
+                }
             )
 
         fs_serializer = EnvironmentFeatureVersionFeatureStateSerializer(
diff --git a/api/tests/unit/features/versioning/test_unit_versioning_views.py b/api/tests/unit/features/versioning/test_unit_versioning_views.py
index b759322c64ea..a3188db5930d 100644
--- a/api/tests/unit/features/versioning/test_unit_versioning_views.py
+++ b/api/tests/unit/features/versioning/test_unit_versioning_views.py
@@ -814,3 +814,79 @@ def test_update_and_create_segment_override_in_single_request(
 
     assert new_version.published is True
     assert new_version.is_live is True
+
+
+def test_create_environment_default_when_creating_new_version_fails(
+    environment_v2_versioning: Environment,
+    feature: Feature,
+    admin_client_new: APIClient,
+) -> None:
+    # Given
+    data = {
+        "feature_states_to_create": [
+            {
+                "feature_segment": None,
+                "enabled": True,
+                "feature_state_value": {
+                    "type": "unicode",
+                    "string_value": "some new value",
+                },
+            }
+        ]
+    }
+
+    url = reverse(
+        "api-v1:versioning:environment-feature-versions-list",
+        args=[environment_v2_versioning.id, feature.id],
+    )
+
+    # When
+    response = admin_client_new.post(
+        url, data=json.dumps(data), content_type="application/json"
+    )
+
+    # Then
+    assert response.status_code == status.HTTP_400_BAD_REQUEST
+
+    assert response.json() == {
+        "feature_states_to_create": "Cannot create FeatureState objects that are not segment overrides."
+    }
+
+
+def test_create_segment_override_for_existing_override_when_creating_new_version_fails(
+    feature: Feature,
+    admin_client_new: APIClient,
+    segment: Segment,
+    segment_featurestate: FeatureState,
+    environment_v2_versioning: Environment,
+) -> None:
+    # Given
+    data = {
+        "feature_states_to_create": [
+            {
+                "feature_segment": {"segment": segment.id},
+                "enabled": True,
+                "feature_state_value": {
+                    "type": "unicode",
+                    "string_value": "some new value",
+                },
+            }
+        ]
+    }
+
+    url = reverse(
+        "api-v1:versioning:environment-feature-versions-list",
+        args=[environment_v2_versioning.id, feature.id],
+    )
+
+    # When
+    response = admin_client_new.post(
+        url, data=json.dumps(data), content_type="application/json"
+    )
+
+    # Then
+    assert response.status_code == status.HTTP_400_BAD_REQUEST
+    assert response.json() == {
+        "feature_states_to_create": "Segment override already exists for Segment %d"
+        % segment.id
+    }

From fd058f95ff0af165f29bd74f37ff19cc534a0d49 Mon Sep 17 00:00:00 2001
From: Matthew Elwell <matthew.elwell@flagsmith.com>
Date: Thu, 23 May 2024 12:05:21 +0100
Subject: [PATCH 12/17] Make new fields write only

---
 api/features/versioning/serializers.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/api/features/versioning/serializers.py b/api/features/versioning/serializers.py
index af72834859c5..92025b2c1f14 100644
--- a/api/features/versioning/serializers.py
+++ b/api/features/versioning/serializers.py
@@ -73,23 +73,27 @@ class EnvironmentFeatureVersionCreateSerializer(EnvironmentFeatureVersionSeriali
             "Array of feature states that will be created in the new version. "
             "Note: these can only include segment overrides."
         ),
+        write_only=True,
     )
     feature_states_to_update = EnvironmentFeatureVersionFeatureStateSerializer(
         many=True,
         allow_null=True,
         required=False,
         help_text="Array of feature states to update in the new version.",
+        write_only=True,
     )
     segment_ids_to_delete_overrides = serializers.ListSerializer(
         child=serializers.IntegerField(),
         required=False,
         allow_null=True,
         help_text="List of segment ids for which the segment overrides will be removed in the new version.",
+        write_only=True,
     )
     publish_immediately = serializers.BooleanField(
         required=False,
         default=False,
         help_text="Boolean to confirm whether the new version should be publish immediately or not.",
+        write_only=True,
     )
 
     class Meta(EnvironmentFeatureVersionSerializer.Meta):

From 1ca8adec66a32f0f904d9e2b3a5b3f2912defb01 Mon Sep 17 00:00:00 2001
From: Matthew Elwell <matthew.elwell@flagsmith.com>
Date: Thu, 23 May 2024 17:54:01 +0100
Subject: [PATCH 13/17] PR feedback

---
 api/features/feature_segments/serializers.py  |  4 ++-
 api/features/versioning/serializers.py        | 25 ++++++++++---------
 .../versioning/test_unit_versioning_views.py  | 25 +++++++++++--------
 3 files changed, 31 insertions(+), 23 deletions(-)

diff --git a/api/features/feature_segments/serializers.py b/api/features/feature_segments/serializers.py
index 541cfaf353fe..017fcdac487d 100644
--- a/api/features/feature_segments/serializers.py
+++ b/api/features/feature_segments/serializers.py
@@ -1,3 +1,5 @@
+import typing
+
 from rest_framework import serializers
 from rest_framework.exceptions import PermissionDenied
 
@@ -46,7 +48,7 @@ class Meta:
         model = FeatureSegment
         fields = ("id", "segment", "priority", "uuid")
 
-    def save(self, **kwargs):
+    def save(self, **kwargs: typing.Any) -> FeatureSegment:
         priority: int | None = self.initial_data.pop("priority", None)
 
         feature_segment: FeatureSegment = super().save(**kwargs)
diff --git a/api/features/versioning/serializers.py b/api/features/versioning/serializers.py
index 92025b2c1f14..7f55a817f760 100644
--- a/api/features/versioning/serializers.py
+++ b/api/features/versioning/serializers.py
@@ -1,3 +1,5 @@
+import typing
+
 from rest_framework import serializers
 
 from features.serializers import CreateSegmentOverrideFeatureStateSerializer
@@ -110,7 +112,9 @@ class Meta(EnvironmentFeatureVersionSerializer.Meta):
             "publish_immediately",
         )
 
-    def create(self, validated_data):
+    def create(
+        self, validated_data: dict[str, typing.Any]
+    ) -> EnvironmentFeatureVersion:
         for field_name in self.Meta.non_model_fields:
             validated_data.pop(field_name, None)
 
@@ -168,23 +172,20 @@ def _create_feature_state(
                 }
             )
 
+        save_kwargs = {
+            "feature": version.feature,
+            "environment": version.environment,
+            "environment_feature_version": version,
+        }
         fs_serializer = EnvironmentFeatureVersionFeatureStateSerializer(
             data=feature_state,
-            context={
-                "feature": version.feature,
-                "environment": version.environment,
-                "environment_feature_version": version,
-            },
+            context=save_kwargs,
         )
         fs_serializer.is_valid(raise_exception=True)
-        fs_serializer.save(
-            environment_feature_version=version,
-            environment=version.environment,
-            feature=version.feature,
-        )
+        fs_serializer.save(**save_kwargs)
 
     def _update_feature_state(
-        self, feature_state: dict, version: EnvironmentFeatureVersion
+        self, feature_state: dict[str, typing.Any], version: EnvironmentFeatureVersion
     ) -> None:
         if self._is_segment_override(feature_state):
             instance = version.feature_states.get(
diff --git a/api/tests/unit/features/versioning/test_unit_versioning_views.py b/api/tests/unit/features/versioning/test_unit_versioning_views.py
index a3188db5930d..ccf74ebf475f 100644
--- a/api/tests/unit/features/versioning/test_unit_versioning_views.py
+++ b/api/tests/unit/features/versioning/test_unit_versioning_views.py
@@ -10,7 +10,10 @@
 from rest_framework.test import APIClient
 
 from environments.models import Environment
-from environments.permissions.constants import VIEW_ENVIRONMENT
+from environments.permissions.constants import (
+    UPDATE_FEATURE_STATE,
+    VIEW_ENVIRONMENT,
+)
 from features.models import Feature, FeatureSegment, FeatureState
 from features.versioning.models import EnvironmentFeatureVersion
 from projects.permissions import VIEW_PROJECT
@@ -70,25 +73,30 @@ def test_get_versions_for_a_feature_and_environment(
 
 
 def test_create_new_feature_version(
-    admin_user: FFAdminUser,
-    admin_client: APIClient,
+    staff_user: FFAdminUser,
+    staff_client: APIClient,
     environment_v2_versioning: Environment,
     feature: Feature,
+    with_environment_permissions: WithEnvironmentPermissionsCallable,
+    with_project_permissions: WithProjectPermissionsCallable,
 ) -> None:
     # Given
+    with_environment_permissions([VIEW_ENVIRONMENT, UPDATE_FEATURE_STATE])
+    with_project_permissions([VIEW_PROJECT])
+
     url = reverse(
         "api-v1:versioning:environment-feature-versions-list",
         args=[environment_v2_versioning.id, feature.id],
     )
 
     # When
-    response = admin_client.post(url)
+    response = staff_client.post(url)
 
     # Then
     assert response.status_code == status.HTTP_201_CREATED
 
     response_json = response.json()
-    assert response_json["created_by"] == admin_user.id
+    assert response_json["created_by"] == staff_user.id
     assert response_json["uuid"]
 
 
@@ -383,7 +391,6 @@ def test_update_environment_feature_version_feature_state(
 
 def test_cannot_update_feature_state_in_published_environment_feature_version(
     admin_client: APIClient,
-    admin_user: FFAdminUser,
     environment_v2_versioning: Environment,
     feature: Feature,
 ) -> None:
@@ -428,7 +435,6 @@ def test_cannot_update_feature_state_in_published_environment_feature_version(
 
 def test_delete_environment_feature_version_feature_state(
     admin_client: APIClient,
-    admin_user: FFAdminUser,
     environment_v2_versioning: Environment,
     segment: Segment,
     feature: Feature,
@@ -519,7 +525,6 @@ def test_cannot_delete_feature_state_in_published_environment_feature_version(
 
 def test_cannot_delete_environment_default_feature_state_for_unpublished_environment_feature_version(
     admin_client: APIClient,
-    admin_user: FFAdminUser,
     environment_v2_versioning: Environment,
     feature: Feature,
 ) -> None:
@@ -741,7 +746,7 @@ def test_update_and_create_segment_override_in_single_request(
     feature: Feature,
     segment: Segment,
     segment_featurestate: FeatureState,
-    admin_client: APIClient,
+    admin_client_new: APIClient,
     environment_v2_versioning: Environment,
 ) -> None:
     # Given
@@ -782,7 +787,7 @@ def test_update_and_create_segment_override_in_single_request(
     }
 
     # When
-    response = admin_client.post(
+    response = admin_client_new.post(
         url, data=json.dumps(data), content_type="application/json"
     )
 

From e624c6a57a1e2e7de5078d72555b33bb1f498329 Mon Sep 17 00:00:00 2001
From: Matthew Elwell <matthew.elwell@flagsmith.com>
Date: Wed, 29 May 2024 18:08:48 +0100
Subject: [PATCH 14/17] Set min priority to 0

---
 api/features/feature_segments/serializers.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/api/features/feature_segments/serializers.py b/api/features/feature_segments/serializers.py
index 017fcdac487d..ff0b58ced4a8 100644
--- a/api/features/feature_segments/serializers.py
+++ b/api/features/feature_segments/serializers.py
@@ -42,7 +42,7 @@ class CreateSegmentOverrideFeatureSegmentSerializer(serializers.ModelSerializer)
     # Since the `priority` field on the FeatureSegment model is set to editable=False
     # (to adhere to the django-ordered-model functionality), we redefine the priority
     # field here, and use it manually in the save method.
-    priority = serializers.IntegerField(min_value=1, required=False)
+    priority = serializers.IntegerField(min_value=0, required=False)
 
     class Meta:
         model = FeatureSegment

From 29a80abc1edd8b399e9dc3d6ca9f6b669b4da796 Mon Sep 17 00:00:00 2001
From: Matthew Elwell <matthew.elwell@flagsmith.com>
Date: Wed, 29 May 2024 18:25:24 +0100
Subject: [PATCH 15/17] Fix issue updating multivariate feature values

---
 api/conftest.py                               |  7 +++
 api/features/versioning/serializers.py        | 16 +++++
 .../versioning/test_unit_versioning_views.py  | 62 +++++++++++++++++++
 3 files changed, 85 insertions(+)

diff --git a/api/conftest.py b/api/conftest.py
index 31bda86c3a84..e852094cdd22 100644
--- a/api/conftest.py
+++ b/api/conftest.py
@@ -446,6 +446,13 @@ def multivariate_feature(project):
     return feature
 
 
+@pytest.fixture()
+def multivariate_options(
+    multivariate_feature: Feature,
+) -> list[MultivariateFeatureOption]:
+    return list(multivariate_feature.multivariate_options.all())
+
+
 @pytest.fixture()
 def identity_matching_segment(project, trait):
     segment = Segment.objects.create(name="Matching segment", project=project)
diff --git a/api/features/versioning/serializers.py b/api/features/versioning/serializers.py
index 7f55a817f760..ef80898cd358 100644
--- a/api/features/versioning/serializers.py
+++ b/api/features/versioning/serializers.py
@@ -197,6 +197,22 @@ def _update_feature_state(
         else:
             instance = version.feature_states.get(feature_segment__isnull=True)
 
+        # TODO: can this be simplified at all?
+        for existing_mvfsv in instance.multivariate_feature_state_values.all():
+            updated_mvfsv_dicts = feature_state.get(
+                "multivariate_feature_state_values", []
+            )
+            updated_mvfsv_dict = next(
+                filter(
+                    lambda d: d["multivariate_feature_option"]
+                    == existing_mvfsv.multivariate_feature_option_id,
+                    updated_mvfsv_dicts,
+                ),
+                None,
+            )
+            if updated_mvfsv_dict:
+                updated_mvfsv_dict["id"] = existing_mvfsv.id
+
         fs_serializer = EnvironmentFeatureVersionFeatureStateSerializer(
             instance=instance,
             data=feature_state,
diff --git a/api/tests/unit/features/versioning/test_unit_versioning_views.py b/api/tests/unit/features/versioning/test_unit_versioning_views.py
index ccf74ebf475f..9197f5dd2322 100644
--- a/api/tests/unit/features/versioning/test_unit_versioning_views.py
+++ b/api/tests/unit/features/versioning/test_unit_versioning_views.py
@@ -3,6 +3,7 @@
 from datetime import datetime, timedelta
 
 import pytest
+from core.constants import STRING
 from django.urls import reverse
 from django.utils import timezone
 from freezegun import freeze_time
@@ -15,6 +16,7 @@
     VIEW_ENVIRONMENT,
 )
 from features.models import Feature, FeatureSegment, FeatureState
+from features.multivariate.models import MultivariateFeatureOption
 from features.versioning.models import EnvironmentFeatureVersion
 from projects.permissions import VIEW_PROJECT
 from segments.models import Segment
@@ -895,3 +897,63 @@ def test_create_segment_override_for_existing_override_when_creating_new_version
         "feature_states_to_create": "Segment override already exists for Segment %d"
         % segment.id
     }
+
+
+def test_create_new_version_for_multivariate_feature(
+    multivariate_feature: Feature,
+    multivariate_options: list[MultivariateFeatureOption],
+    environment_v2_versioning: Environment,
+    staff_client: APIClient,
+    with_environment_permissions: WithEnvironmentPermissionsCallable,
+    with_project_permissions: WithProjectPermissionsCallable,
+) -> None:
+    # Given
+    with_environment_permissions(
+        [VIEW_ENVIRONMENT, UPDATE_FEATURE_STATE], environment_v2_versioning.id
+    )
+    with_project_permissions([VIEW_PROJECT])
+
+    create_version_url = reverse(
+        "api-v1:versioning:environment-feature-versions-list",
+        args=[environment_v2_versioning.id, multivariate_feature.id],
+    )
+
+    data = {
+        "feature_states_to_update": [
+            {
+                "feature_segment": None,
+                "enabled": True,
+                "feature_state_value": {
+                    "type": STRING,
+                    "string_value": multivariate_feature.initial_value,
+                },
+                "multivariate_feature_state_values": [
+                    {
+                        "multivariate_feature_option": mvfo.id,
+                        "percentage_allocation": 10,
+                    }
+                    for mvfo in multivariate_options
+                ],
+            }
+        ]
+    }
+
+    # When
+    response = staff_client.post(
+        create_version_url, data=json.dumps(data), content_type="application/json"
+    )
+
+    # Then
+    assert response.status_code == status.HTTP_201_CREATED
+
+    version_uuid = response.json()["uuid"]
+    new_version = EnvironmentFeatureVersion.objects.get(uuid=version_uuid)
+
+    assert all(
+        [
+            mvfsv.percentage_allocation == 10
+            for mvfsv in new_version.feature_states.get(
+                feature=multivariate_feature
+            ).multivariate_feature_state_values.all()
+        ]
+    )

From 3dfa2a67069735c7e88231d2445e10a8651f23f4 Mon Sep 17 00:00:00 2001
From: Matthew Elwell <matthew.elwell@flagsmith.com>
Date: Mon, 3 Jun 2024 19:32:38 +0100
Subject: [PATCH 16/17] Delete the feature segments (which cascade to the
 feature states) instead of feature states

---
 api/features/versioning/serializers.py        |  4 +-
 .../versioning/test_unit_versioning_views.py  | 39 +++++++++++++++++++
 2 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/api/features/versioning/serializers.py b/api/features/versioning/serializers.py
index 14d14466061e..d4442c916c11 100644
--- a/api/features/versioning/serializers.py
+++ b/api/features/versioning/serializers.py
@@ -254,9 +254,7 @@ def _update_feature_state(
     def _delete_feature_states(
         self, segment_ids: list[int], version: EnvironmentFeatureVersion
     ) -> None:
-        version.feature_states.filter(
-            feature_segment__segment_id__in=segment_ids
-        ).delete()
+        version.feature_segments.filter(segment_id__in=segment_ids).delete()
 
     def _is_segment_override(self, feature_state: dict) -> bool:
         return feature_state.get("feature_segment") is not None
diff --git a/api/tests/unit/features/versioning/test_unit_versioning_views.py b/api/tests/unit/features/versioning/test_unit_versioning_views.py
index f96fd6aacd83..09e42cfc2552 100644
--- a/api/tests/unit/features/versioning/test_unit_versioning_views.py
+++ b/api/tests/unit/features/versioning/test_unit_versioning_views.py
@@ -1085,3 +1085,42 @@ def test_create_new_version_for_multivariate_feature(
             ).multivariate_feature_state_values.all()
         ]
     )
+
+
+def test_create_new_version_delete_segment_override_updates_overrides_immediately(
+    feature: Feature,
+    segment: Segment,
+    feature_segment: FeatureSegment,
+    segment_featurestate: FeatureState,
+    environment_v2_versioning: Environment,
+    admin_client: APIClient,
+) -> None:
+    # Given
+    create_version_url = reverse(
+        "api-v1:versioning:environment-feature-versions-list",
+        args=[environment_v2_versioning.id, feature.id],
+    )
+
+    data = {
+        "segment_ids_to_delete_overrides": [segment.id],
+        "publish_immediately": True,
+    }
+
+    # When
+    response = admin_client.post(
+        create_version_url,
+        data=json.dumps(data),
+        content_type="application/json",
+    )
+
+    # Then
+    assert response.status_code == status.HTTP_201_CREATED
+
+    get_feature_segments_url = "%s?environment=%d&feature=%d" % (
+        reverse("api-v1:features:feature-segment-list"),
+        environment_v2_versioning.id,
+        feature.id,
+    )
+    get_feature_segments_response = admin_client.get(get_feature_segments_url)
+    assert get_feature_segments_response.status_code == status.HTTP_200_OK
+    assert get_feature_segments_response.json()["count"] == 0

From ce87fe034d93cdaf58cb498d4fe30324ac47bc35 Mon Sep 17 00:00:00 2001
From: Matthew Elwell <matthew.elwell@flagsmith.com>
Date: Mon, 24 Jun 2024 11:45:12 +0100
Subject: [PATCH 17/17] Move / improve comment

---
 api/features/versioning/serializers.py | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/api/features/versioning/serializers.py b/api/features/versioning/serializers.py
index d4442c916c11..9774961b4274 100644
--- a/api/features/versioning/serializers.py
+++ b/api/features/versioning/serializers.py
@@ -139,15 +139,16 @@ class Meta(EnvironmentFeatureVersionSerializer.Meta):
     def create(
         self, validated_data: dict[str, typing.Any]
     ) -> EnvironmentFeatureVersion:
+        # Note that we use self.initial_data below for handling the feature states
+        # since we want the raw data (rather than the serialized ORM objects) to pass
+        # into the serializers in the separate private methods used for modifying the
+        # FeatureState objects. As such, we just want to blindly remove the non-model
+        # attribute keys from the validated before calling super to create the version.
         for field_name in self.Meta.non_model_fields:
             validated_data.pop(field_name, None)
 
         version = super().create(validated_data)
 
-        # Note that we use self.initial_data for handling the feature states here
-        # since we want the raw data (rather than the serialized ORM objects) to
-        # pass into the serializers in the separate private methods used for modifying
-        # the FeatureState objects.
         for feature_state_to_create in self.initial_data.get(
             "feature_states_to_create", []
         ):