[#351] ✨ Use JSON Merge Patch when doing a partial update on records

src/objects/api/serializers.py

@@ -10,6 +10,7 @@
 
 from .fields import ObjectSlugRelatedField, ObjectTypeField, ObjectUrlField
 from .validators import GeometryValidator, IsImmutableValidator, JsonSchemaValidator
+from .utils import merge_patch
 
 
 class ObjectRecordSerializer(serializers.ModelSerializer):
@@ -129,6 +130,11 @@ def update(self, instance, validated_data):
         # in case of PATCH
         if "version" not in validated_data:
             validated_data["version"] = instance.version
+            if "data" in validated_data:
+                # Apply JSON Merge Patch for record data
+                validated_data["data"] = merge_patch(
+                    instance.data, validated_data["data"]
+                )
 
         record = super().create(validated_data)
         return record

src/objects/api/utils.py

@@ -1,5 +1,5 @@
 from datetime import date
-from typing import Union
+from typing import Any, Dict, Union
 
 from djchoices import DjangoChoices
 
@@ -43,3 +43,22 @@ def display_choice_values_for_help_text(choices: DjangoChoices) -> str:
         items.append(item)
 
     return "\n".join(items)
+
+
+def merge_patch(target: Any, patch: Any) -> Dict[str, Any]:
+    """An implementation of https://datatracker.ietf.org/doc/html/rfc7396 - JSON Merge Patch"""
+    if not isinstance(patch, dict):
+        return patch
+
+    if not isinstance(target, dict):
+        # Ignore the contents and set it to an empty dict
+        target = {}
+    for k, v in patch.items():
+        if v is None:
+            if k in target:
+                # remove the key/value pair from target
+                del target[k]
+        else:
+            target[k] = merge_patch(target.get(k), v)
+
+    return target

src/objects/tests/test_merge_patch.py

@@ -0,0 +1,29 @@
+from unittest import TestCase
+
+from objects.api.utils import merge_patch
+
+
+class MergePatchTests(TestCase):
+    def test_merge_patch(self):
+
+        test_data = [
+            ({"a": "b"}, {"a": "c"}, {"a": "c"}),
+            ({"a": "b"}, {"b": "c"}, {"a": "b", "b": "c"}),
+            ({"a": "b"}, {"a": None}, {}),
+            ({"a": "b", "b": "c"}, {"a": None}, {"b": "c"}),
+            ({"a": ["b"]}, {"a": "c"}, {"a": "c"}),
+            ({"a": "c"}, {"a": ["b"]}, {"a": ["b"]}),
+            ({"a": {"b": "c"}}, {"a": {"b": "d", "c": None}}, {"a": {"b": "d"}}),
+            ({"a": [{"b": "c"}]}, {"a": [1]}, {"a": [1]}),
+            (["a", "b"], ["c", "d"], ["c", "d"]),
+            ({"a": "b"}, ["c"], ["c"]),
+            ({"a": "foo"}, None, None),
+            ({"a": "foo"}, "bar", "bar"),
+            ({"e": None}, {"a": 1}, {"e": None, "a": 1}),
+            ([1, 2], {"a": "b", "c": None}, {"a": "b"}),
+            ({}, {"a": {"bb": {"ccc": None}}}, {"a": {"bb": {}}}),
+        ]
+
+        for target, patch, expected in test_data:
+            with self.subTest():
+                self.assertEqual(merge_patch(target, patch), expected)

src/objects/tests/v1/test_object_api.py

@@ -205,7 +205,10 @@ def test_patch_object_record(self, m):
         )
 
         initial_record = ObjectRecordFactory.create(
-            version=1, object__object_type=self.object_type, start_at=date.today()
+            version=1,
+            object__object_type=self.object_type,
+            start_at=date.today(),
+            data={"name": "Name", "diameter": 20},
         )
         object = initial_record.object
 
@@ -229,8 +232,10 @@ def test_patch_object_record(self, m):
         current_record = object.current_record
 
         self.assertEqual(current_record.version, initial_record.version)
+        # The actual behavior of the data merging is in test_merge_patch.py:
         self.assertEqual(
-            current_record.data, {"plantDate": "2020-04-12", "diameter": 30}
+            current_record.data,
+            {"plantDate": "2020-04-12", "diameter": 30, "name": "Name"},
         )
         self.assertEqual(current_record.start_at, date(2020, 1, 1))
         self.assertEqual(current_record.registration_at, date(2020, 8, 8))

src/objects/tests/v2/test_object_api.py

@@ -227,7 +227,10 @@ def test_patch_object_record(self, m):
         )
 
         initial_record = ObjectRecordFactory.create(
-            version=1, object__object_type=self.object_type, start_at=date.today()
+            version=1,
+            object__object_type=self.object_type,
+            start_at=date.today(),
+            data={"name": "Name", "diameter": 20},
         )
         object = initial_record.object
 
@@ -251,8 +254,10 @@ def test_patch_object_record(self, m):
         current_record = object.current_record
 
         self.assertEqual(current_record.version, initial_record.version)
+        # The actual behavior of the data merging is in test_merge_patch.py:
         self.assertEqual(
-            current_record.data, {"plantDate": "2020-04-12", "diameter": 30}
+            current_record.data,
+            {"plantDate": "2020-04-12", "diameter": 30, "name": "Name"},
         )
         self.assertEqual(current_record.start_at, date(2020, 1, 1))
         self.assertEqual(current_record.registration_at, date(2020, 8, 8))