Enable existing_image on PATCH requests (#6126)

* Enable existing_image on PATCH requests

* Fix CI problems

* Solution

* Change check to whitelist and add unit tests

InvenTree/part/serializers.py

@@ -617,7 +617,10 @@ class PartSerializer(
 
         if not create:
             # These fields are only used for the LIST API endpoint
-            for f in self.skip_create_fields()[1:]:
+            for f in self.skip_create_fields():
+                # Fields required for certain operations, but are not part of the model
+                if f in ["remote_image", "existing_image"]:
+                    continue
                 self.fields.pop(f)
 
         if not pricing:

InvenTree/part/test_api.py

@@ -1575,6 +1575,64 @@ class PartDetailTests(PartAPITestBase):
 
         self.assertEqual(response.data['image'], image_name)
 
+    def test_update_existing_image(self):
+        """Test that we can update the image of an existing part with an already existing image"""
+        # First, upload an image for an existing part
+        p = Part.objects.first()
+
+        fn = 'part_image_123abc.png'
+
+        img = PIL.Image.new('RGB', (128, 128), color='blue')
+        img.save(fn)
+
+        # Upload the image to a part
+        with open(fn, 'rb') as img_file:
+            response = self.upload_client.patch(
+                reverse('api-part-detail', kwargs={'pk': p.pk}),
+                {
+                    'image': img_file,
+                },
+            )
+
+            self.assertEqual(response.status_code, 200)
+            image_name = response.data['image']
+            self.assertTrue(image_name.startswith('/media/part_images/part_image'))
+
+        # Create a new part without an image
+        response = self.post(
+            reverse('api-part-list'),
+            {
+                'name': 'Some New Part',
+                'description': 'Description of the part',
+                'category': 1
+            },
+            expected_code=201
+        )
+
+        self.assertEqual(response.data['image'], None)
+        part_pk = response.data['pk']
+
+        # Add image from the first part to the new part
+        response = self.patch(
+            reverse('api-part-detail', kwargs={'pk': part_pk}),
+            {
+                'existing_image': image_name
+            },
+            expected_code=200
+        )
+
+        self.assertEqual(response.data['image'], image_name)
+
+        # Attempt to add a non-existent image to an existing part
+        last_p = Part.objects.last()
+        response = self.patch(
+            reverse('api-part-detail', kwargs={'pk': last_p.pk}),
+            {
+                'existing_image': 'bogus_image.jpg'
+            },
+            expected_code=400
+        )
+
     def test_details(self):
         """Test that the required details are available."""
         p = Part.objects.get(pk=1)