fix(query-builder): returnFields should be '*' on entity change / all fileds are selected (#15445)

* fix(query-builder): returnFields should be '*' on entity change
---------

Author: teodosiah

projects/igniteui-angular/src/lib/query-builder/query-builder-tree.component.ts

@@ -610,7 +610,9 @@ export class IgxQueryBuilderTreeComponent implements AfterViewInit, OnDestroy {
 
         if (this._expressionTree) {
             this._expressionTree.entity = this._entityNewValue.name;
-            this._expressionTree.returnFields = [];
+
+            this._expressionTree.returnFields = this.fields.length === this._selectedReturnFields.length ? ['*'] : this._selectedReturnFields;
+
             this._expressionTree.filteringOperands = [];
 
             this._editedExpression = null;
@@ -643,7 +645,7 @@ export class IgxQueryBuilderTreeComponent implements AfterViewInit, OnDestroy {
             this._selectedReturnFields = value;
 
             if (this._expressionTree && !this.parentExpression) {
-                this._expressionTree.returnFields = value;
+                this._expressionTree.returnFields = value.length === this.fields.length ? ['*'] : value;
                 this.expressionTreeChange.emit(this._expressionTree);
             }
         }

projects/igniteui-angular/src/lib/query-builder/query-builder.component.spec.ts

@@ -444,6 +444,56 @@ describe('IgxQueryBuilder', () => {
       expect((dropdownItems[4] as HTMLElement).innerText).toBe('Released');
     }));
 
+    it('ReturnFields should be properly calculated on entity change.', fakeAsync(() => {
+      queryBuilder.expressionTree = QueryBuilderFunctions.generateExpressionTree();
+      queryBuilder.showEntityChangeDialog = false;
+      fix.detectChanges();
+
+      // Verify the returnFields
+      let exprTreeReturnFields = JSON.stringify(fix.componentInstance.queryBuilder.expressionTree.returnFields);
+      expect(exprTreeReturnFields).toBe(`["*"]`);
+      
+      // Change the selected return fields
+      QueryBuilderFunctions.selectFieldsInEditModeExpression(fix, [1]);
+      tick(100);
+      fix.detectChanges();
+       
+      // Verify the returnFields
+      exprTreeReturnFields = JSON.stringify(fix.componentInstance.queryBuilder.expressionTree.returnFields);
+      expect(exprTreeReturnFields).toBe(`["OrderId"]`);
+      
+      // Change the entity
+      QueryBuilderFunctions.selectEntityAndClickInitialAddCondition(fix, 0);
+
+      // Verify the returnFields
+      exprTreeReturnFields = JSON.stringify(fix.componentInstance.queryBuilder.expressionTree.returnFields);
+      expect(exprTreeReturnFields).toBe(`["*"]`);
+    }));
+
+    it('ReturnFields should be properly calculated on selectAll click.', fakeAsync(() => {
+      queryBuilder.expressionTree = QueryBuilderFunctions.generateExpressionTree();
+      queryBuilder.showEntityChangeDialog = false;
+      fix.detectChanges();
+      
+      // Click selectAll button in order to deselect all fields
+      QueryBuilderFunctions.selectFieldsInEditModeExpression(fix, [0]);
+      tick(100);
+      fix.detectChanges();
+       
+      // Verify the returnFields
+      let exprTreeReturnFields = JSON.stringify(fix.componentInstance.queryBuilder.expressionTree.returnFields);
+      expect(exprTreeReturnFields).toBe(`[]`);
+      
+      // Click selectAll button in order to select all fields
+      QueryBuilderFunctions.selectFieldsInEditModeExpression(fix, [0]);
+      tick(100);
+      fix.detectChanges();
+
+      // Verify the returnFields
+      exprTreeReturnFields = JSON.stringify(fix.componentInstance.queryBuilder.expressionTree.returnFields);
+      expect(exprTreeReturnFields).toBe(`["*"]`);
+    }));
+
     it('Column dropdown should contain proper fields based on the entity.', fakeAsync(() => {
       const queryBuilderElement: HTMLElement = fix.debugElement.queryAll(By.css(`.${QueryBuilderSelectors.QUERY_BUILDER_TREE}`))[0].nativeElement;