working on merge transfer

src/backend/InvenTree/common/setting/system.py

@@ -787,6 +787,15 @@ SYSTEM_SETTINGS: dict[str, InvenTreeSettingsKeyType] = {
         'default': False,
         'validator': bool,
     },
+    'STOCK_MERGE_ON_TRANSFER': {
+        'name': _('Merge stock with existing stock on transfer'),
+        'description': _(
+            'Default: when transferring stock, merge into an existing lot at the '
+            'destination if possible (uses the same rules as manual stock merge)'
+        ),
+        'default': False,
+        'validator': bool,
+    },
     'BUILDORDER_REFERENCE_PATTERN': {
         'name': _('Build Order Reference Pattern'),
         'description': _('Required pattern for generating Build Order reference field'),

src/backend/InvenTree/stock/models.py

@@ -2179,6 +2179,34 @@ class StockItem(
 
         return True
 
+    def find_merge_target(self, location):
+        """Find an existing stock item at *location* that can absorb this item."""
+        if location is None:
+            return None
+
+        candidates = list(
+            StockItem.objects.filter(part=self.part, location=location)
+            .exclude(pk=self.pk)
+            .order_by('pk')
+        )
+
+        if not candidates:
+            return None
+
+        if self.batch:
+            batch_matches = [c for c in candidates if c.batch == self.batch]
+            search_order = batch_matches + [
+                c for c in candidates if c not in batch_matches
+            ]
+        else:
+            search_order = candidates
+
+        for target in search_order:
+            if target.can_merge(other=self, raise_error=False):
+                return target
+
+        return None
+
     @transaction.atomic
     def merge_stock_items(self, other_items, raise_error=False, **kwargs):
         """Merge another stock item into this one; the two become one!
@@ -2186,7 +2214,7 @@ class StockItem(
         *This* stock item subsumes the other, which is essentially deleted:
 
         - The quantity of this StockItem is increased
-        - Tracking history for the *other* item is deleted
+        - Tracking history for the *other* item is copied to this item
         - Any allocations (build order, sales order) are moved to this StockItem
         """
         if isinstance(other_items, StockItem):
@@ -2200,7 +2228,7 @@ class StockItem(
 
         user = kwargs.get('user')
         location = kwargs.get('location', self.location)
-        notes = kwargs.get('notes')
+        notes = kwargs.get('notes') or ''
 
         parent_id = self.parent.pk if self.parent else None
 
@@ -2242,6 +2270,18 @@ class StockItem(
                 self.parent = None
                 self.save()
 
+            self.copyHistoryFrom(other)
+
+            if other.location:
+                location_note = _('Transferred from %(location)s') % {
+                    'location': other.location.pathstring
+                }
+
+                if notes:
+                    notes = f'{notes}\n{location_note}'
+                else:
+                    notes = location_note
+
             other.delete()
 
         self.add_tracking_entry(

src/backend/InvenTree/stock/serializers.py

@@ -1829,7 +1829,7 @@ class StockTransferSerializer(StockAdjustmentSerializer):
     class Meta:
         """Metaclass options."""
 
-        fields = ['items', 'notes', 'location']
+        fields = ['items', 'notes', 'location', 'merge']
 
     items = StockAdjustmentItemSerializer(many=True, require_non_zero=True)
 
@@ -1842,6 +1842,15 @@ class StockTransferSerializer(StockAdjustmentSerializer):
         help_text=_('Destination stock location'),
     )
 
+    merge = serializers.BooleanField(
+        default=False,
+        required=False,
+        label=_('Merge into existing stock'),
+        help_text=_(
+            'Merge transferred items into existing stock items at the destination if possible'
+        ),
+    )
+
     def save(self):
         """Transfer stock."""
         request = self.context['request']
@@ -1851,6 +1860,7 @@ class StockTransferSerializer(StockAdjustmentSerializer):
         items = data['items']
         notes = data.get('notes', '')
         location = data['location']
+        merge = data.get('merge', False)
 
         with transaction.atomic():
             for item in items:
@@ -1865,6 +1875,34 @@ class StockTransferSerializer(StockAdjustmentSerializer):
                     if field_value := item.get(field_name, None):
                         kwargs[field_name] = field_value
 
+                if merge:
+                    target = stock_item.find_merge_target(location)
+
+                    if target:
+                        merge_kwargs = {
+                            'location': location,
+                            'notes': notes,
+                            'user': request.user,
+                            **kwargs,
+                        }
+
+                        if quantity < stock_item.quantity:
+                            piece = stock_item.splitStock(
+                                quantity,
+                                location,
+                                request.user,
+                                notes=notes,
+                                allow_production=True,
+                                **kwargs,
+                            )
+                            target.merge_stock_items([piece], **merge_kwargs)
+                        else:
+                            target.merge_stock_items(
+                                [stock_item], **merge_kwargs
+                            )
+
+                        continue
+
                 stock_item.move(
                     location, notes, request.user, quantity=quantity, **kwargs
                 )

src/backend/InvenTree/stock/test_api.py

@@ -2154,6 +2154,106 @@ class StocktakeTest(StockAPITestCase):
         )
 
 
+class StockTransferMergeTest(StockAPITestCase):
+    """Tests for optional merge-on-transfer behavior."""
+
+    def setUp(self):
+        """Set up stock items for merge transfer tests."""
+        super().setUp()
+
+        self.part = Part.objects.get(pk=1)
+        self.dest = StockLocation.objects.get(pk=2)
+        self.source_loc = StockLocation.objects.get(pk=5)
+        self.url = reverse('api-stock-transfer')
+
+    def test_transfer_without_merge_creates_separate_lot(self):
+        """Transfer without merge leaves multiple stock rows at destination."""
+        existing = StockItem.objects.create(
+            part=self.part, location=self.dest, quantity=100
+        )
+        incoming = StockItem.objects.create(
+            part=self.part, location=self.source_loc, quantity=50
+        )
+
+        self.post(
+            self.url,
+            {
+                'items': [{'pk': incoming.pk, 'quantity': 50}],
+                'location': self.dest.pk,
+                'merge': False,
+            },
+            expected_code=201,
+        )
+
+        self.assertEqual(
+            StockItem.objects.filter(part=self.part, location=self.dest).count(), 2
+        )
+
+        existing.refresh_from_db()
+        self.assertEqual(existing.quantity, 100)
+
+    def test_transfer_with_merge_combines_lots(self):
+        """Transfer with merge combines into an existing compatible lot."""
+        existing = StockItem.objects.create(
+            part=self.part, location=self.dest, quantity=100
+        )
+        incoming = StockItem.objects.create(
+            part=self.part, location=self.source_loc, quantity=50
+        )
+
+        self.post(
+            self.url,
+            {
+                'items': [{'pk': incoming.pk, 'quantity': 50}],
+                'location': self.dest.pk,
+                'merge': True,
+            },
+            expected_code=201,
+        )
+
+        self.assertEqual(
+            StockItem.objects.filter(part=self.part, location=self.dest).count(), 1
+        )
+
+        existing.refresh_from_db()
+        self.assertEqual(existing.quantity, 150)
+        self.assertFalse(StockItem.objects.filter(pk=incoming.pk).exists())
+
+    def test_transfer_merge_preserves_tracking(self):
+        """Transfer merge copies tracking history onto the surviving stock item."""
+        existing = StockItem.objects.create(
+            part=self.part, location=self.dest, quantity=100
+        )
+        incoming = StockItem.objects.create(
+            part=self.part, location=self.source_loc, quantity=50
+        )
+
+        incoming.add_tracking_entry(
+            StockHistoryCode.STOCK_UPDATE,
+            self.user,
+            notes='Source tracking entry',
+        )
+
+        tracking_count = existing.tracking_info.count()
+
+        self.post(
+            self.url,
+            {
+                'items': [{'pk': incoming.pk, 'quantity': 50}],
+                'location': self.dest.pk,
+                'merge': True,
+            },
+            expected_code=201,
+        )
+
+        existing.refresh_from_db()
+
+        self.assertTrue(
+            existing.tracking_info.filter(notes='Source tracking entry').exists()
+        )
+        self.assertGreater(existing.tracking_info.count(), tracking_count)
+
+
 class StockItemDeletionTest(StockAPITestCase):
     """Tests for stock item deletion via the API."""
 

src/backend/InvenTree/stock/tests.py

@@ -722,12 +722,24 @@ class StockTest(StockTestBase):
         s2 = StockItem.objects.create(part=part, quantity=20)
         s3 = StockItem.objects.create(part=part, quantity=30)
 
+        s2.add_tracking_entry(
+            StockHistoryCode.STOCK_UPDATE,
+            None,
+            notes='Merged away tracking',
+        )
+
+        tracking_before = s1.tracking_info.count()
+
         self.assertEqual(part.stock_items.count(), 3)
         s1.merge_stock_items([s2, s3])
         self.assertEqual(part.stock_items.count(), 1)
         s1.refresh_from_db()
         self.assertEqual(s1.quantity, 60)
         self.assertIsNone(s1.purchase_price)
+        self.assertTrue(
+            s1.tracking_info.filter(notes='Merged away tracking').exists()
+        )
+        self.assertGreater(s1.tracking_info.count(), tracking_before)
 
         part.stock_items.all().delete()
 

src/frontend/src/forms/StockForms.tsx

@@ -20,7 +20,14 @@ import {
   IconUsersGroup
 } from '@tabler/icons-react';
 import { useQuery, useSuspenseQuery } from '@tanstack/react-query';
-import { type JSX, Suspense, useEffect, useMemo, useState } from 'react';
+import {
+  type JSX,
+  Suspense,
+  useCallback,
+  useEffect,
+  useMemo,
+  useState
+} from 'react';
 
 import { ActionButton } from '@lib/components/ActionButton';
 import { ApiEndpoints } from '@lib/enums/ApiEndpoints';
@@ -1319,9 +1326,21 @@ export function useRemoveStockItem(props: StockOperationProps) {
 }
 
 export function useTransferStockItem(props: StockOperationProps) {
+  const globalSettings = useGlobalSettingsState();
+
+  const fieldGenerator = useCallback(
+    (items: any[]) => ({
+      ...stockTransferFields(items),
+      merge: {
+        default: globalSettings.isSet('STOCK_MERGE_ON_TRANSFER')
+      }
+    }),
+    [globalSettings]
+  );
+
   return useStockOperationModal({
     ...props,
-    fieldGenerator: stockTransferFields,
+    fieldGenerator: fieldGenerator,
     endpoint: ApiEndpoints.stock_transfer,
     title: t`Transfer Stock`,
     successMessage: t`Stock transferred`,

src/frontend/src/pages/Index/Settings/SystemSettings.tsx

@@ -259,6 +259,7 @@ export default function SystemSettings() {
                 'STOCK_SHOW_INSTALLED_ITEMS',
                 'STOCK_ENFORCE_BOM_INSTALLATION',
                 'STOCK_ALLOW_OUT_OF_STOCK_TRANSFER',
+                'STOCK_MERGE_ON_TRANSFER',
                 'TEST_STATION_DATA'
               ]}
             />

src/frontend/vite.config.ts

@@ -82,6 +82,7 @@ export default defineConfig(({ command, mode }) => {
           changeOrigin: true,
           secure: true
         }
+        
       },
       watch: {
         // Use polling only for WSL as the file system doesn't trigger notifications for Linux apps