Fix for parametric part table

- Only display parameters for which we know there is a value

src/backend/InvenTree/common/api.py

@@ -27,6 +27,7 @@ from rest_framework.exceptions import NotAcceptable, NotFound, PermissionDenied
 from rest_framework.permissions import IsAdminUser, IsAuthenticated
 from rest_framework.response import Response
 from rest_framework.views import APIView
+from sql_util.utils import SubqueryCount
 
 import common.filters
 import common.models
@@ -820,6 +821,27 @@ class ParameterTemplateFilter(FilterSet):
             queryset, 'model_type', value, allow_null=True
         )
 
+    exists_for_model = rest_filters.CharFilter(
+        method='filter_exists_for_model', label='Exists For Model'
+    )
+
+    def filter_exists_for_model(self, queryset, name, value):
+        """Filter queryset to include only ParameterTemplates which have at least one Parameter for the given model type."""
+        content_type = common.filters.determine_content_type(value)
+
+        if not content_type:
+            return queryset.none()
+
+        # Annotate the queryset to determine which ParameterTemplates have at least one Parameter for the given model type
+        queryset = queryset.annotate(
+            parameter_count=SubqueryCount(
+                'parameters', filter=Q(model_type=content_type)
+            )
+        )
+
+        # Return only those ParameterTemplates which have at least one Parameter for the given model type
+        return queryset.filter(parameter_count__gt=0)
+
 
 class ParameterTemplateMixin:
     """Mixin class for ParameterTemplate views."""

src/backend/InvenTree/common/filters.py

@@ -21,22 +21,17 @@ import InvenTree.conversion
 import InvenTree.helpers
 
 
-def filter_content_type(
-    queryset, field_name: str, content_type: str | int | None, allow_null: bool = True
-):
-    """Filter a queryset by content type.
+def determine_content_type(content_type: str | int | None) -> ContentType | None:
+    """Determine a ContentType instance from a string or integer input.
 
     Arguments:
-        queryset: The queryset to filter.
-        field_name: The name of the content type field within the current model context.
-        content_type: The content type to filter by (name or ID).
-        allow_null: If True, include entries with null content type.
+        content_type: The content type to resolve (name or ID).
 
     Returns:
-        Filtered queryset.
+        ContentType instance if found, else None.
     """
     if content_type is None:
-        return queryset
+        return None
 
     ct = None
 
@@ -59,6 +54,28 @@ def filter_content_type(
         # Next, try to resolve the content type via a model name
         ct = ContentType.objects.filter(model__iexact=content_type).first()
 
+    return ct
+
+
+def filter_content_type(
+    queryset, field_name: str, content_type: str | int | None, allow_null: bool = True
+):
+    """Filter a queryset by content type.
+
+    Arguments:
+        queryset: The queryset to filter.
+        field_name: The name of the content type field within the current model context.
+        content_type: The content type to filter by (name or ID).
+        allow_null: If True, include entries with null content type.
+
+    Returns:
+        Filtered queryset.
+    """
+    if content_type is None:
+        return queryset
+
+    ct = determine_content_type(content_type)
+
     if ct is None:
         raise ValueError(f'Invalid content type: {content_type}')