fix(igxGrid): Reset autogenerated columns in case Ivy triggers a ContentChildren re-evaluation that clears them.

Author: MKirova

projects/igniteui-angular/src/lib/grids/grid-base.directive.ts

@@ -2468,6 +2468,7 @@ export class IgxGridBaseDirective extends DisplayDensityBase implements
     private _unpinnedWidth = NaN;
     private _visibleColumns = [];
     private _columnGroups = false;
+    private _autoGeneratedCols = [];
     protected _headerFeaturesWidth = NaN;
 
     private _columnWidth: string;
@@ -4543,10 +4544,16 @@ export class IgxGridBaseDirective extends DisplayDensityBase implements
      */
     protected onColumnsChanged(change: QueryList<IgxColumnComponent>) {
         const diff = this.columnListDiffer.diff(change);
+        if (this.autoGenerate && this.columnList.length === 0 && this._autoGeneratedCols.length > 0) {
+            // In Ivy if there are nested conditional templates the content children are re-evaluated
+            // hence autogenerated columns are cleared and need to be reset.
+            this.columnList.reset(this._autoGeneratedCols);
+            return;
+        }
         if (diff) {
             let added = false;
             let removed = false;
-
+            
             this.initColumns(this.columnList);
 
 
@@ -4772,6 +4779,7 @@ export class IgxGridBaseDirective extends DisplayDensityBase implements
             ref.changeDetectorRef.detectChanges();
             columns.push(ref.instance);
         });
+        this._autoGeneratedCols = columns;
 
         this.columnList.reset(columns);
         if (data && data.length > 0) {

projects/igniteui-angular/src/lib/grids/hierarchical-grid/hierarchical-grid.component.ts

@@ -417,7 +417,7 @@ export class IgxHierarchicalGridComponent extends IgxHierarchicalGridBaseDirecti
     protected onColumnsChanged(change: QueryList<IgxColumnComponent>) {
         this.updateColumnList();
         const cols = change.filter(c => c.gridAPI.grid === this);
-        if (cols.length > 0) {
+        if (cols.length > 0 || this.autoGenerate) {
             this.columnList.reset(cols);
             super.onColumnsChanged(this.columnList);
         }

projects/igniteui-angular/src/lib/grids/hierarchical-grid/hierarchical-grid.spec.ts

@@ -1080,8 +1080,7 @@ describe('IgxHierarchicalGrid Runtime Row Island change Scenarios #hGrid', () =>
         hierarchicalGrid = fixture.componentInstance.hgrid;
     }));
 
-    xit('should allow changing row islands runtime in root grid.', () => {
-        pending('Related to issue #6731');
+    it('should allow changing row islands runtime in root grid.', () => {
         const row = hierarchicalGrid.getRowByIndex(0) as IgxHierarchicalRowComponent;
         UIInteractions.clickElement(row.expander);
         fixture.detectChanges();