From e1e04329637d5d1b410911108dcc3389c267ea61 Mon Sep 17 00:00:00 2001
From: Oliver <oliver.henry.walters@gmail.com>
Date: Tue, 26 Apr 2022 10:57:43 +1000
Subject: [PATCH 1/3] Adds 'variant_of' filter back into Part API

---
 InvenTree/InvenTree/api_version.py |  5 ++++-
 InvenTree/part/api.py              | 12 ++++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/InvenTree/InvenTree/api_version.py b/InvenTree/InvenTree/api_version.py
index 7851efd8dd..f767148199 100644
--- a/InvenTree/InvenTree/api_version.py
+++ b/InvenTree/InvenTree/api_version.py
@@ -4,11 +4,14 @@ InvenTree API version information
 
 
 # InvenTree API version
-INVENTREE_API_VERSION = 40
+INVENTREE_API_VERSION = 41
 
 """
 Increment this API version number whenever there is a significant change to the API that any clients need to know about
 
+v41 -> 2022-04-26
+    - Fixes 'variant_of' filter for Part list endpoint
+
 v40 -> 2022-04-19
     - Adds ability to filter StockItem list by "tracked" parameter
         - This checks the serial number or batch code fields
diff --git a/InvenTree/part/api.py b/InvenTree/part/api.py
index de6cd4a974..e394efae7e 100644
--- a/InvenTree/part/api.py
+++ b/InvenTree/part/api.py
@@ -1175,6 +1175,18 @@ class PartList(generics.ListCreateAPIView):
             except (ValueError, Part.DoesNotExist):
                 pass
 
+        # Filter by 'variant_of'
+        # Note that this is subtly different from 'ancestor' filter (above)
+        variant_of = params.get('variant_of', None)
+
+        if variant_of is not None:
+            try:
+                template = Part.objects.get(pk=variant_of)
+                variants = template.get_children()
+                queryset = queryset.filter(pk__in=[v.pk for v in variants])
+            except (ValueError, Part.DoesNotExist):
+                pass
+
         # Filter only parts which are in the "BOM" for a given part
         in_bom_for = params.get('in_bom_for', None)
 

From 693e47ab891328357d355e1932b58f7b2d9d93ea Mon Sep 17 00:00:00 2001
From: Oliver <oliver.henry.walters@gmail.com>
Date: Tue, 26 Apr 2022 11:02:22 +1000
Subject: [PATCH 2/3] Remove outdated filter_fields variable

---
 InvenTree/part/api.py | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/InvenTree/part/api.py b/InvenTree/part/api.py
index e394efae7e..b025791a7f 100644
--- a/InvenTree/part/api.py
+++ b/InvenTree/part/api.py
@@ -1351,10 +1351,6 @@ class PartList(generics.ListCreateAPIView):
         filters.OrderingFilter,
     ]
 
-    filter_fields = [
-        'variant_of',
-    ]
-
     ordering_fields = [
         'name',
         'creation_date',

From 70d4960fa30ae26afdb342931532f2a07bc70828 Mon Sep 17 00:00:00 2001
From: Oliver <oliver.henry.walters@gmail.com>
Date: Tue, 26 Apr 2022 11:43:34 +1000
Subject: [PATCH 3/3] Add new unit tests for part API filters

---
 InvenTree/part/fixtures/part.yaml |  1 +
 InvenTree/part/test_api.py        | 91 +++++++++++++++++++++++++++++++
 2 files changed, 92 insertions(+)

diff --git a/InvenTree/part/fixtures/part.yaml b/InvenTree/part/fixtures/part.yaml
index d0a2d949b1..fd38036fa9 100644
--- a/InvenTree/part/fixtures/part.yaml
+++ b/InvenTree/part/fixtures/part.yaml
@@ -177,6 +177,7 @@
   fields:
     name: 'Green chair variant'
     variant_of: 10003
+    is_template: true
     category: 7
     trackable: true
     tree_id: 1
diff --git a/InvenTree/part/test_api.py b/InvenTree/part/test_api.py
index 5a8acbecd9..ddfaa44e94 100644
--- a/InvenTree/part/test_api.py
+++ b/InvenTree/part/test_api.py
@@ -567,6 +567,97 @@ class PartAPITest(InvenTreeAPITestCase):
         self.assertEqual(response.data['name'], name)
         self.assertEqual(response.data['description'], description)
 
+    def test_template_filters(self):
+        """
+        Unit tests for API filters related to template parts:
+
+        - variant_of : Return children of specified part
+        - ancestor : Return descendants of specified part
+
+        Uses the 'chair template' part (pk=10000)
+        """
+
+        # Rebuild the MPTT structure before running these tests
+        Part.objects.rebuild()
+
+        url = reverse('api-part-list')
+
+        response = self.get(
+            url,
+            {
+                'variant_of': 10000,
+            },
+            expected_code=200
+        )
+
+        # 3 direct children of template part
+        self.assertEqual(len(response.data), 3)
+
+        response = self.get(
+            url,
+            {
+                'ancestor': 10000,
+            },
+            expected_code=200,
+        )
+
+        # 4 total descendants
+        self.assertEqual(len(response.data), 4)
+
+        # Use the 'green chair' as our reference
+        response = self.get(
+            url,
+            {
+                'variant_of': 10003,
+            },
+            expected_code=200,
+        )
+
+        self.assertEqual(len(response.data), 1)
+
+        response = self.get(
+            url,
+            {
+                'ancestor': 10003,
+            },
+            expected_code=200,
+        )
+
+        self.assertEqual(len(response.data), 1)
+
+        # Add some more variants
+
+        p = Part.objects.get(pk=10004)
+
+        for i in range(100):
+            Part.objects.create(
+                name=f'Chair variant {i}',
+                description='A new chair variant',
+                variant_of=p,
+            )
+
+        # There should still be only one direct variant
+        response = self.get(
+            url,
+            {
+                'variant_of': 10003,
+            },
+            expected_code=200,
+        )
+
+        self.assertEqual(len(response.data), 1)
+
+        # However, now should be 101 descendants
+        response = self.get(
+            url,
+            {
+                'ancestor': 10003,
+            },
+            expected_code=200,
+        )
+
+        self.assertEqual(len(response.data), 101)
+
 
 class PartDetailTests(InvenTreeAPITestCase):
     """