Fix: backwards-compatible versioned API response for custom field select fields (#8912)

src/documents/serialisers.py

@@ -496,6 +496,15 @@ class StoragePathField(serializers.PrimaryKeyRelatedField):
 
 
 class CustomFieldSerializer(serializers.ModelSerializer):
+    def __init__(self, *args, **kwargs):
+        context = kwargs.get("context")
+        self.api_version = int(
+            context.get("request").version
+            if context.get("request")
+            else settings.REST_FRAMEWORK["DEFAULT_VERSION"],
+        )
+        super().__init__(*args, **kwargs)
+
     data_type = serializers.ChoiceField(
         choices=CustomField.FieldDataType,
         read_only=False,
@@ -575,6 +584,38 @@ class CustomFieldSerializer(serializers.ModelSerializer):
             )
         return super().validate(attrs)
 
+    def to_internal_value(self, data):
+        ret = super().to_internal_value(data)
+
+        if (
+            self.api_version < 7
+            and ret.get("data_type", "") == CustomField.FieldDataType.SELECT
+            and isinstance(ret.get("extra_data", {}).get("select_options"), list)
+        ):
+            ret["extra_data"]["select_options"] = [
+                {
+                    "label": option,
+                    "id": get_random_string(length=16),
+                }
+                for option in ret["extra_data"]["select_options"]
+            ]
+
+        return ret
+
+    def to_representation(self, instance):
+        ret = super().to_representation(instance)
+
+        if (
+            self.api_version < 7
+            and instance.data_type == CustomField.FieldDataType.SELECT
+        ):
+            # Convert the select options with ids to a list of strings
+            ret["extra_data"]["select_options"] = [
+                option["label"] for option in ret["extra_data"]["select_options"]
+            ]
+
+        return ret
+
 
 class ReadWriteSerializerMethodField(serializers.SerializerMethodField):
     """
@@ -682,6 +723,50 @@ class CustomFieldInstanceSerializer(serializers.ModelSerializer):
 
         return data
 
+    def get_api_version(self):
+        return int(
+            self.context.get("request").version
+            if self.context.get("request")
+            else settings.REST_FRAMEWORK["DEFAULT_VERSION"],
+        )
+
+    def to_internal_value(self, data):
+        ret = super().to_internal_value(data)
+
+        if (
+            self.get_api_version() < 7
+            and ret.get("field").data_type == CustomField.FieldDataType.SELECT
+            and ret.get("value") is not None
+        ):
+            # Convert the index of the option in the field.extra_data["select_options"]
+            # list to the options unique id
+            ret["value"] = ret.get("field").extra_data["select_options"][ret["value"]][
+                "id"
+            ]
+
+        return ret
+
+    def to_representation(self, instance):
+        ret = super().to_representation(instance)
+
+        if (
+            self.get_api_version() < 7
+            and instance.field.data_type == CustomField.FieldDataType.SELECT
+        ):
+            # return the index of the option in the field.extra_data["select_options"] list
+            ret["value"] = next(
+                (
+                    idx
+                    for idx, option in enumerate(
+                        instance.field.extra_data["select_options"],
+                    )
+                    if option["id"] == instance.value
+                ),
+                None,
+            )
+
+        return ret
+
     def reflect_doclinks(
         self,
         document: Document,