From c3182fedd9f7171c001cd9128cb5cd6741da8f69 Mon Sep 17 00:00:00 2001
From: igdmdimitrov <dmdimitrov@infragistics.com>
Date: Fri, 4 Jul 2025 16:52:37 +0300
Subject: [PATCH 1/2] fix(query-builder): improve isAdvancedFiltering check

---
 .../query-builder-tree.component.html         |  4 +--
 .../query-builder-tree.component.ts           |  2 +-
 .../query-builder.component.spec.ts           | 28 +++++++++++++++++++
 3 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/projects/igniteui-angular/src/lib/query-builder/query-builder-tree.component.html b/projects/igniteui-angular/src/lib/query-builder/query-builder-tree.component.html
index 7e167a243c7..ea92b146cca 100644
--- a/projects/igniteui-angular/src/lib/query-builder/query-builder-tree.component.html
+++ b/projects/igniteui-angular/src/lib/query-builder/query-builder-tree.component.html
@@ -75,7 +75,7 @@
                     (selectionChanging)="onReturnFieldSelectChanging($event)"
                     [overlaySettings]="returnFieldSelectOverlaySettings"
                     [disabled]="!selectedEntity"
-                    [ngModel]="selectedReturnFields[0]"
+                    [ngModel]="selectedReturnFields ? selectedReturnFields[0] : null"
                     [placeholder]="this.resourceStrings.igx_query_builder_select_return_field_single"
                     [style.display]="isInEditMode() ? 'block' : 'none'"
                     (opening)="exitEditAddMode()"
@@ -466,7 +466,7 @@
                 <ng-container>
                     <igx-query-builder-tree
                         [style.display]="expressionItem.inEditMode || expressionItem.expanded ? 'block' : 'none'"
-                        [entities]="(this.selectedEntity ? this.selectedEntity.childEntities : entities[0].childEntities) ?? entities"
+                        [entities]="(this.selectedEntity ? this.selectedEntity.childEntities : entities[0]?.childEntities) ?? entities"
                         [queryBuilder]="this.queryBuilder"
                         [parentExpression]="expressionItem"
                         [expectedReturnField]="this.selectedField?.field"
diff --git a/projects/igniteui-angular/src/lib/query-builder/query-builder-tree.component.ts b/projects/igniteui-angular/src/lib/query-builder/query-builder-tree.component.ts
index 7a59165e80c..f456b40dbc7 100644
--- a/projects/igniteui-angular/src/lib/query-builder/query-builder-tree.component.ts
+++ b/projects/igniteui-angular/src/lib/query-builder/query-builder-tree.component.ts
@@ -523,7 +523,7 @@ export class IgxQueryBuilderTreeComponent implements AfterViewInit, OnDestroy {
     protected isAdvancedFiltering(): boolean {
         return (this.entities?.length === 1 && !this.entities[0]?.name) ||
             this.entities?.find(e => e.childEntities?.length > 0) !== undefined ||
-            this.entities !== this.queryBuilder?.entities;
+            (this.entities?.length > 0 && this.queryBuilder?.entities?.length > 0 && this.entities !== this.queryBuilder?.entities);
     }
 
     /** @hidden */
diff --git a/projects/igniteui-angular/src/lib/query-builder/query-builder.component.spec.ts b/projects/igniteui-angular/src/lib/query-builder/query-builder.component.spec.ts
index ec9722cd1ef..894876c3423 100644
--- a/projects/igniteui-angular/src/lib/query-builder/query-builder.component.spec.ts
+++ b/projects/igniteui-angular/src/lib/query-builder/query-builder.component.spec.ts
@@ -127,6 +127,13 @@ describe('IgxQueryBuilder', () => {
         expect(field.pipeArgs).toBeUndefined();
       });
     }));
+
+    it('Should not throw error when entities are empty and expressionTree is set.', fakeAsync(() => {
+      expect(() => {
+        fix = TestBed.createComponent(IgxQueryBuilderInvalidSampleTestComponent);
+        fix.detectChanges();
+      }).not.toThrow();
+    }));
   });
 
   describe('Interactions', () => {
@@ -3234,6 +3241,27 @@ export class IgxQueryBuilderSampleTestComponent implements OnInit {
   }
 }
 
+@Component({
+  template: `
+     <igx-query-builder #queryBuilder [entities]="this.entities" [expressionTree]="this.expressionTree">
+     </igx-query-builder>
+    `,
+  standalone: true,
+  imports: [
+    IgxQueryBuilderComponent
+  ]
+})
+export class IgxQueryBuilderInvalidSampleTestComponent implements OnInit {
+  @ViewChild(IgxQueryBuilderComponent) public queryBuilder: IgxQueryBuilderComponent;
+  public entities: Array<any>;
+  public expressionTree: IExpressionTree;
+
+  public ngOnInit(): void {
+    this.entities = [];
+    this.expressionTree = QueryBuilderFunctions.generateExpressionTree();
+  }
+}
+
 @Component({
   template: `
      <igx-query-builder #queryBuilder [entities]="this.entities" [expressionTree]="this.expressionTree">

From 0b912cb553267e6b4e0f38e3f07af84526b13688 Mon Sep 17 00:00:00 2001
From: igdmdimitrov <dmdimitrov@infragistics.com>
Date: Tue, 8 Jul 2025 16:39:01 +0300
Subject: [PATCH 2/2] chore(*): add additional checks when entities is not set

---
 .../src/lib/query-builder/query-builder-tree.component.html     | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/projects/igniteui-angular/src/lib/query-builder/query-builder-tree.component.html b/projects/igniteui-angular/src/lib/query-builder/query-builder-tree.component.html
index ea92b146cca..9adc2116b0d 100644
--- a/projects/igniteui-angular/src/lib/query-builder/query-builder-tree.component.html
+++ b/projects/igniteui-angular/src/lib/query-builder/query-builder-tree.component.html
@@ -466,7 +466,7 @@
                 <ng-container>
                     <igx-query-builder-tree
                         [style.display]="expressionItem.inEditMode || expressionItem.expanded ? 'block' : 'none'"
-                        [entities]="(this.selectedEntity ? this.selectedEntity.childEntities : entities[0]?.childEntities) ?? entities"
+                        [entities]="(this.selectedEntity ? this.selectedEntity.childEntities : entities?.[0]?.childEntities) ?? (entities ?? [])"
                         [queryBuilder]="this.queryBuilder"
                         [parentExpression]="expressionItem"
                         [expectedReturnField]="this.selectedField?.field"