feat(entity view): add nullsFirst option (#494)

* fix(entity view): null values are properly sorted

* fix(entity): undefined, null and empty string are properly sorted

* fix(view): naturalCompare is fixed, no need to separate undefined and null values first

packages/common/src/lib/entity/entity-table/entity-table.component.ts

@@ -76,6 +76,12 @@ export class EntityTableComponent implements OnInit, OnDestroy, OnChanges  {
   @Input()
   scrollBehavior: EntityTableScrollBehavior = EntityTableScrollBehavior.Auto;
 
+  /**
+   * Whether nulls should be first when sorting
+   */
+  @Input()
+  sortNullsFirst: boolean = false;
+
   /**
    * Event emitted when an entity (row) is clicked
    */
@@ -196,7 +202,8 @@ export class EntityTableComponent implements OnInit, OnDestroy, OnChanges  {
     if (direction === 'asc' || direction === 'desc') {
       this.store.view.sort({
         valueAccessor: (entity: object) => this.getValue(entity, column),
-        direction
+        direction,
+        nullsFirst: this.sortNullsFirst
       });
     } else {
       this.store.view.sort(undefined);

packages/common/src/lib/entity/shared/entity.interfaces.ts

@@ -36,6 +36,12 @@ export type EntityFilterClause<E = object> = (entity: E) => boolean;
 export interface EntitySortClause<E = object> {
   valueAccessor: (entity: E) => string | number;
   direction: string;
+
+  // If true, null and undefined values will be first
+  // If false, null and undefined values will be last
+  // If undefined, default to true and false when sorting in descending and
+  // ascending order, respectively
+  nullsFirst?: boolean;
 }
 
 export interface EntityJoinClause {

packages/common/src/lib/entity/shared/view.ts

@@ -255,7 +255,7 @@ export class EntityView<E extends object, V extends object = E> {
         clause.valueAccessor(v1),
         clause.valueAccessor(v2),
         clause.direction,
-        false
+        clause.nullsFirst
       );
     });
   }