Maybe hack-y but working custom field serialization

src/documents/migrations/1040_customfield_customfieldboolean_customfielddate_and_more.py

@@ -1,4 +1,4 @@
-# Generated by Django 4.2.5 on 2023-10-28 02:54
+# Generated by Django 4.2.5 on 2023-10-31 17:28
 
 import django.db.models.deletion
 import django.utils.timezone
@@ -92,16 +92,6 @@ class Migration(migrations.Migration):
                         to="documents.customfield",
                     ),
                 ),
-                (
-                    "owner",
-                    models.ForeignKey(
-                        blank=True,
-                        null=True,
-                        on_delete=django.db.models.deletion.SET_NULL,
-                        to=settings.AUTH_USER_MODEL,
-                        verbose_name="owner",
-                    ),
-                ),
             ],
             options={
                 "verbose_name": "custom field instance",
@@ -229,4 +219,11 @@ class Migration(migrations.Migration):
                 ),
             ],
         ),
+        migrations.AddConstraint(
+            model_name="customfieldinstance",
+            constraint=models.UniqueConstraint(
+                fields=("document", "field"),
+                name="documents_customfieldinstance_unique_document_field",
+            ),
+        ),
     ]

src/documents/models.py

@@ -4,6 +4,7 @@ import os
 import re
 from collections import OrderedDict
 from pathlib import Path
+from typing import Any
 from typing import Final
 from typing import Optional
 
@@ -920,7 +921,7 @@ class CustomField(models.Model):
         return f"{self.name} : {self.data_type}"
 
 
-class CustomFieldInstance(ModelWithOwner):
+class CustomFieldInstance(models.Model):
     """
     A single instance of a field, attached to a CustomField for the name and type
     and attached to a single Document to be metadata for it
@@ -952,6 +953,12 @@ class CustomFieldInstance(ModelWithOwner):
         ordering = ("created",)
         verbose_name = _("custom field instance")
         verbose_name_plural = _("custom field instances")
+        constraints = [
+            models.UniqueConstraint(
+                fields=["document", "field"],
+                name="%(app_label)s_%(class)s_unique_document_field",
+            ),
+        ]
 
     def __str__(self) -> str:
         return str(self.field) + f" : {self.value}"
@@ -1002,17 +1009,19 @@ class CustomFieldInstance(ModelWithOwner):
     @staticmethod
     def from_json(
         document: Document,
-        field: CustomField,
-        data,
+        field: OrderedDict,
+        value: Any,
     ) -> "CustomFieldInstance":
-        instance = CustomFieldInstance.objects.create(
+        instance, _ = CustomFieldInstance.objects.get_or_create(
             document=document,
-            field=field,
-            data_type=data["type"],
+            field=CustomField.objects.get(id=field["id"]),
+        )
+        instance.field_type.objects.update_or_create(
+            parent=instance,
+            defaults={"value": value},
         )
-        instance.field_type.objects.create(value=data["value"], parent=instance)
 
-        return field
+        return instance
 
 
 class CustomFieldShortText(models.Model):

src/documents/serialisers.py

@@ -2,6 +2,7 @@ import datetime
 import math
 import re
 import zoneinfo
+from typing import Any
 
 import magic
 from celery import states
@@ -406,26 +407,16 @@ class CustomFieldSerializer(serializers.ModelSerializer):
         ]
 
 
-class CustomFieldInstanceSerializer(serializers.ModelSerializer):
-    parent = CustomFieldSerializer()
+class CustomFieldInstanceSerializer(serializers.Serializer):
+    field = CustomFieldSerializer(required=True)
     value = SerializerMethodField()
 
     def get_value(self, obj: CustomFieldInstance):
         return obj.value
 
-    def create(self, validated_data):
-        parent_data = validated_data.pop("parent")
-        parent = CustomField.objects.get(id=parent_data["id"])
-        instance = CustomFieldInstance.objects.create(parent=parent)
-        return instance
-
-    def update(self, instance: CustomFieldInstance):
-        return instance
-
     class Meta:
-        model = CustomFieldInstance
         fields = [
-            "parent",
+            "field",
             "value",
         ]
 
@@ -463,7 +454,25 @@ class DocumentSerializer(OwnedObjectSerializer, DynamicFieldsModelSerializer):
             doc["content"] = doc.get("content")[0:550]
         return doc
 
+    def to_internal_value(self, data: Any) -> Any:
+        # hack-y
+        values = super().to_internal_value(data)
+        if "custom_fields" in values:
+            for index, field_instance in enumerate(values["custom_fields"]):
+                data_custom_field = data["custom_fields"][index]
+                field_instance["field"]["id"] = data_custom_field["field"]["id"]
+                field_instance["value"] = data_custom_field["value"]
+        return values
+
     def update(self, instance, validated_data):
+        if "custom_fields" in validated_data:
+            custom_fields = validated_data.pop("custom_fields")
+            for field_data in custom_fields:
+                CustomFieldInstance.from_json(
+                    document=instance,
+                    field=field_data["field"],
+                    value=field_data["value"],
+                )
         if "created_date" in validated_data and "created" not in validated_data:
             new_datetime = datetime.datetime.combine(
                 validated_data.get("created_date"),