[DataGridPro] Data source: Allow expanding groups with unknown children (@MBilalShafi) (#17149)

Signed-off-by: Bilal Shafi <bilalshafidev@gmail.com>
Co-authored-by: Bilal Shafi <bilalshafidev@gmail.com>

Author: github-actions[bot]

packages/x-data-grid-premium/src/components/GridDataSourceGroupingCriteriaCell.tsx

@@ -73,7 +73,7 @@ function GridGroupingCriteriaCellIcon(props: GridGroupingCriteriaCellIconProps)
     );
   }
 
-  return descendantCount > 0 ? (
+  return descendantCount === -1 || descendantCount > 0 ? (
     <rootProps.slots.baseIconButton
       size="small"
       onClick={handleClick}
@@ -105,7 +105,7 @@ export function GridDataSourceGroupingCriteriaCell(props: GridGroupingCriteriaCe
 
   let descendantCount = 0;
   if (row) {
-    descendantCount = Math.max(rootProps.unstable_dataSource?.getChildrenCount?.(row) ?? 0, 0);
+    descendantCount = rootProps.unstable_dataSource?.getChildrenCount?.(row) ?? 0;
   }
 
   let cellContent: React.ReactNode;

packages/x-data-grid-pro/src/components/GridDataSourceTreeDataGroupingCell.tsx

@@ -80,7 +80,8 @@ function GridTreeDataGroupingCellIcon(props: GridTreeDataGroupingCellIconProps)
       </div>
     );
   }
-  return descendantCount > 0 ? (
+
+  return descendantCount === -1 || descendantCount > 0 ? (
     <rootProps.slots.baseIconButton
       size="small"
       onClick={handleClick}
@@ -112,7 +113,7 @@ export function GridDataSourceTreeDataGroupingCell(props: GridTreeDataGroupingCe
 
   let descendantCount = 0;
   if (row) {
-    descendantCount = Math.max(rootProps.unstable_dataSource?.getChildrenCount?.(row) ?? 0, 0);
+    descendantCount = rootProps.unstable_dataSource?.getChildrenCount?.(row) ?? 0;
   }
 
   return (