Validate uniqueness for StockItems

- If the Part is a variant of a template, ensure that the serial numbers are unique across all instances of the template
- Prevent instantiation of a StockItem for a part which has variants

InvenTree/stock/migrations/0003_auto_20190525_2303.py

@@ -0,0 +1,19 @@
+# Generated by Django 2.2 on 2019-05-25 13:03
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('stock', '0002_auto_20190525_2226'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='stockitem',
+            name='part',
+            field=models.ForeignKey(help_text='Base part', limit_choices_to={'active': True, 'has_variants': False}, on_delete=django.db.models.deletion.CASCADE, related_name='stock_items', to='part.Part'),
+        ),
+    ]

InvenTree/stock/models.py

@@ -115,6 +115,23 @@ class StockItem(models.Model):
                 system=True
             )
 
+    def validate_unique(self, exclude=None):
+        super(StockItem, self).validate_unique(exclude)
+
+        # If the Part object is a variant (of a template part),
+        # ensure that the serial number is unique
+        # across all variants of the same template part
+
+
+        try:
+            if self.serial is not None and self.part.variant_of is not None:
+                if StockItem.objects.filter(part__variant_of=self.part.variant_of, serial=self.serial).exclude(id=self.id).exists():
+                    raise ValidationError({
+                        'serial': _('A part with this serial number already exists for template part {part}'.format(part=self.part.variant_of))
+                    })
+        except Part.DoesNotExist:
+            pass
+
     def clean(self):
         """ Validate the StockItem object (separate to field validation)
 
@@ -196,7 +213,7 @@ class StockItem(models.Model):
     part = models.ForeignKey('part.Part', on_delete=models.CASCADE,
                             related_name='stock_items', help_text='Base part',
                             limit_choices_to={
-                                'has_variants': True,
+                                'has_variants': False,
                                 'active': True,
                             })
 

InvenTree/stock/views.py

@@ -208,13 +208,19 @@ class StockItemCreate(AjaxCreateView):
 
             try:
                 part = Part.objects.get(id=part_id)
-                parts = form.fields['supplier_part'].queryset
+                # Hide the 'part' field (as a valid part is selected)
-                parts = parts.filter(part=part.id)
+                form.fields['part'].widget = HiddenInput()
+                
 
                 # If the part is NOT purchaseable, hide the supplier_part field
                 if not part.purchaseable:
                     form.fields['supplier_part'].widget = HiddenInput()
 
+                else:
+                    # Pre-select the allowable SupplierPart options
+                    parts = form.fields['supplier_part'].queryset
+                    parts = parts.filter(part=part.id)
+
                     form.fields['supplier_part'].queryset = parts
 
                     # If there is one (and only one) supplier part available, pre-select it
@@ -227,9 +233,6 @@ class StockItemCreate(AjaxCreateView):
             except Part.DoesNotExist:
                 pass
 
-            # Hide the 'part' field
-            form.fields['part'].widget = HiddenInput()
-
         # Otherwise if the user has selected a SupplierPart, we know what Part they meant!
         elif form['supplier_part'].value() is not None:
             pass