Check for (and reduce) overallocated stock when editing build orders. (#3237)

* Check for (and reduce) overallocated stock when editing build orders.

After a build order is edited, check whether any bom items are now
overallocated to the build, and if they are find appropriate build items to
reduce the quantity of or remove from the build.

Fixes: #3236

* Only trim overallocated stock if requested

Turns the complete with overallocated stock option into a choice, so the
user can reject (default), continue (existing option in the bool), or
now additionally instead choose to have the overallocated stock removed
before the build is completed.

* fix style errors

* Another style fix.

* Add tests for overallocation handling API logic

* Capitalize overallocation options.

InvenTree/build/test_api.py

@@ -717,6 +717,105 @@ class BuildAllocationTest(BuildAPITest):
         self.assertEqual(allocation.stock_item.pk, 2)
 
 
+class BuildOverallocationTest(BuildAPITest):
+    """Unit tests for over allocation of stock items against a build order.
+
+    Using same Build ID=1 as allocation test above.
+    """
+
+    def setUp(self):
+        """Basic operation as part of test suite setup"""
+        super().setUp()
+
+        self.assignRole('build.add')
+        self.assignRole('build.change')
+
+        self.build = Build.objects.get(pk=1)
+        self.url = reverse('api-build-finish', kwargs={'pk': self.build.pk})
+
+        StockItem.objects.create(part=Part.objects.get(pk=50), quantity=30)
+
+        # Keep some state for use in later assertions, and then overallocate
+        self.state = {}
+        self.allocation = {}
+        for i, bi in enumerate(self.build.part.bom_items.all()):
+            rq = self.build.required_quantity(bi, None) + i + 1
+            si = StockItem.objects.filter(part=bi.sub_part, quantity__gte=rq).first()
+
+            self.state[bi.sub_part] = (si, si.quantity, rq)
+            BuildItem.objects.create(
+                build=self.build,
+                stock_item=si,
+                quantity=rq,
+            )
+
+        # create and complete outputs
+        self.build.create_build_output(self.build.quantity)
+        outputs = self.build.build_outputs.all()
+        self.build.complete_build_output(outputs[0], self.user)
+
+        # Validate expected state after set-up.
+        self.assertEqual(self.build.incomplete_outputs.count(), 0)
+        self.assertEqual(self.build.complete_outputs.count(), 1)
+        self.assertEqual(self.build.completed, self.build.quantity)
+
+    def test_overallocated_requires_acceptance(self):
+        """Test build order cannot complete with overallocated items."""
+        # Try to complete the build (it should fail due to overallocation)
+        response = self.post(
+            self.url,
+            {},
+            expected_code=400
+        )
+        self.assertTrue('accept_overallocated' in response.data)
+
+        # Check stock items have not reduced at all
+        for si, oq, _ in self.state.values():
+            si.refresh_from_db()
+            self.assertEqual(si.quantity, oq)
+
+        # Accept overallocated stock
+        self.post(
+            self.url,
+            {
+                'accept_overallocated': 'accept',
+            },
+            expected_code=201,
+        )
+
+        self.build.refresh_from_db()
+
+        # Build should have been marked as complete
+        self.assertTrue(self.build.is_complete)
+
+        # Check stock items have reduced in-line with the overallocation
+        for si, oq, rq in self.state.values():
+            si.refresh_from_db()
+            self.assertEqual(si.quantity, oq - rq)
+
+    def test_overallocated_can_trim(self):
+        """Test build order will trim/de-allocate overallocated stock when requested."""
+        self.post(
+            self.url,
+            {
+                'accept_overallocated': 'trim',
+            },
+            expected_code=201,
+        )
+
+        self.build.refresh_from_db()
+
+        # Build should have been marked as complete
+        self.assertTrue(self.build.is_complete)
+
+        # Check stock items have reduced only by bom requirement (overallocation trimmed)
+        for bi in self.build.part.bom_items.all():
+            si, oq, _ = self.state[bi.sub_part]
+            rq = self.build.required_quantity(bi, None)
+            si.refresh_from_db()
+            self.assertEqual(si.quantity, oq - rq)
+
+
 class BuildListTest(BuildAPITest):
     """Tests for the BuildOrder LIST API."""