Created PartCategoryParameterTemplate model and admin interface

InvenTree/part/admin.py

@@ -12,6 +12,7 @@ from .models import PartCategory, Part
 from .models import PartAttachment, PartStar
 from .models import BomItem
 from .models import PartParameterTemplate, PartParameter
+from .models import PartCategoryParameterTemplate
 from .models import PartTestTemplate
 from .models import PartSellPriceBreak
 
@@ -269,6 +270,18 @@ class ParameterAdmin(ImportExportModelAdmin):
     list_display = ('part', 'template', 'data')
 
 
+class PartCategoryParameterAdmin(admin.ModelAdmin):
+
+    def get_form(self, request, obj=None, **kwargs):
+        """ Display only parent categories as choices for category field """
+
+        form = super().get_form(request, obj, **kwargs)
+
+        form.base_fields['category'].choices = PartCategory.get_parent_categories()
+
+        return form
+
+
 class PartSellPriceBreakAdmin(admin.ModelAdmin):
 
     class Meta:
@@ -284,5 +297,6 @@ admin.site.register(PartStar, PartStarAdmin)
 admin.site.register(BomItem, BomItemAdmin)
 admin.site.register(PartParameterTemplate, ParameterTemplateAdmin)
 admin.site.register(PartParameter, ParameterAdmin)
+admin.site.register(PartCategoryParameterTemplate, PartCategoryParameterAdmin)
 admin.site.register(PartTestTemplate, PartTestTemplateAdmin)
 admin.site.register(PartSellPriceBreak, PartSellPriceBreakAdmin)

InvenTree/part/migrations/0053_partcategoryparametertemplate.py

@@ -0,0 +1,27 @@
+# Generated by Django 3.0.7 on 2020-10-30 18:04
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('part', '0052_auto_20201027_1557'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='PartCategoryParameterTemplate',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('default_value', models.CharField(blank=True, help_text='Default Parameter Value', max_length=500)),
+                ('category', models.ForeignKey(help_text='Part Category', on_delete=django.db.models.deletion.CASCADE, related_name='parameter_templates', to='part.PartCategory')),
+                ('parameter_template', models.ForeignKey(help_text='Parameter Template', on_delete=django.db.models.deletion.CASCADE, related_name='part_categories', to='part.PartParameterTemplate')),
+            ],
+        ),
+        migrations.AddConstraint(
+            model_name='partcategoryparametertemplate',
+            constraint=models.UniqueConstraint(fields=('category', 'parameter_template'), name='unique_category_parameter_template_pair'),
+        ),
+    ]

InvenTree/part/models.py

@@ -12,7 +12,7 @@ from django.core.exceptions import ValidationError
 from django.urls import reverse
 
 from django.db import models, transaction
-from django.db.models import Sum
+from django.db.models import Sum, UniqueConstraint
 from django.db.models.functions import Coalesce
 from django.core.validators import MinValueValidator
 
@@ -163,6 +163,22 @@ class PartCategory(InvenTreeTree):
 
         return category_parameters
 
+    @classmethod
+    def get_parent_categories(cls):
+        """ Return tuple list of parent (root) categories """
+
+        # Store parent categories (add empty label)
+        parent_categories = [
+            ('', '-' * 10)
+        ]
+        # Get root nodes
+        root_categories = cls.objects.filter(level=0)
+
+        for category in root_categories:
+            parent_categories.append((category.id, category.name))
+
+        return parent_categories
+
 
 @receiver(pre_delete, sender=PartCategory, dispatch_uid='partcategory_delete_log')
 def before_delete_part_category(sender, instance, using, **kwargs):
@@ -1550,6 +1566,48 @@ class PartParameter(models.Model):
         return part_parameter
 
 
+class PartCategoryParameterTemplate(models.Model):
+    """
+    A PartCategoryParameterTemplate creates a unique relationship between a PartCategory
+    and a PartParameterTemplate.
+    Multiple PartParameterTemplate instances can be associated to a PartCategory to drive
+    a default list of parameter templates attached to a Part instance upon creation.
+
+    Attributes:
+        category: Reference to a single PartCategory object
+        parameter_template: Reference to a single PartParameterTemplate object
+        default_value: The default value for the parameter in the context of the selected
+                       category
+    """
+
+    class Meta:
+        constraints = [
+            UniqueConstraint(fields=['category', 'parameter_template'],
+                             name='unique_category_parameter_template_pair')
+        ]
+
+    def __str__(self):
+        """ String representation of a PartCategoryParameterTemplate (admin interface) """
+        if self.default_value:
+            return f'{self.category.name} | {self.parameter_template.name} | {self.default_value}'
+        else:
+            return f'{self.category.name} | {self.parameter_template.name}'
+
+    category = models.ForeignKey(PartCategory,
+                                 on_delete=models.CASCADE,
+                                 related_name='parameter_templates',
+                                 help_text=_('Part Category'))
+
+    parameter_template = models.ForeignKey(PartParameterTemplate,
+                                           on_delete=models.CASCADE,
+                                           related_name='part_categories',
+                                           help_text=_('Parameter Template'))
+
+    default_value = models.CharField(max_length=500,
+                                     blank=True,
+                                     help_text=_('Default Parameter Value'))
+
+
 class BomItem(models.Model):
     """ A BomItem links a part to its component items.
     A part can have a BOM (bill of materials) which defines