fix(dashboard): sort datasets by creation time (newest first)

frontend/src/app/dashboard/component/user/sort-button/sort-button.component.html

@@ -34,27 +34,31 @@
 
 <nz-dropdown-menu #sortOptions="nzDropdownMenu">
   <ul nz-menu>
+    @if (showEditTime) {
     <li nz-menu-item>
       <button
         (click)="lastSort()"
         nz-button>
         By Edit Time
       </button>
     </li>
+    }
     <li nz-menu-item>
       <button
         (click)="dateSort()"
         nz-button>
         By Create Time
       </button>
     </li>
+    @if (showExecutionTime) {
     <li nz-menu-item>
       <button
         (click)="execSort()"
         nz-button>
         By Execution Time
       </button>
     </li>
+    }
     <li nz-menu-item>
       <button
         (click)="ascSort()"

frontend/src/app/dashboard/component/user/sort-button/sort-button.component.spec.ts

@@ -76,4 +76,21 @@ describe("SortButtonComponent", () => {
     expect(component.sortMethod).toBe(SortMethod.ExecutionTimeDesc);
     expect(emitSpy).toHaveBeenCalledWith(SortMethod.ExecutionTimeDesc);
   });
+
+  // Note: the sort options render inside an nz-dropdown-menu (a CDK overlay) that
+  // does not attach under the vitest/jsdom test environment, so we can't assert on
+  // the rendered menu text. We instead verify the input contract that the template's
+  // @if guards bind to (showEditTime / showExecutionTime).
+  it("shows the edit-time and execution-time options by default (e.g. for workflows)", () => {
+    expect(component.showEditTime).toBe(true);
+    expect(component.showExecutionTime).toBe(true);
+  });
+
+  it("can hide edit-time and execution-time options (e.g. for datasets, which have neither)", () => {
+    component.showEditTime = false;
+    component.showExecutionTime = false;
+    fixture.detectChanges();
+    expect(component.showEditTime).toBe(false);
+    expect(component.showExecutionTime).toBe(false);
+  });
 });

frontend/src/app/dashboard/component/user/sort-button/sort-button.component.ts

@@ -17,7 +17,7 @@
  * under the License.
  */
 
-import { Component, EventEmitter, Output } from "@angular/core";
+import { Component, EventEmitter, Input, Output } from "@angular/core";
 import { SortMethod } from "../../../type/sort-method";
 import { NzDropdownADirective, NzDropdownDirective, NzDropdownMenuComponent } from "ng-zorro-antd/dropdown";
 import { NzSpaceCompactItemDirective } from "ng-zorro-antd/space";
@@ -47,6 +47,14 @@ import { NzMenuDirective, NzMenuItemComponent } from "ng-zorro-antd/menu";
 export class SortButtonComponent {
   @Output()
   public sortMethodChange = new EventEmitter<SortMethod>();
+
+  // Some resource types (e.g. datasets) have no edit or execution timestamp; hide the
+  // corresponding options so they can't produce an undefined (NULL) sort order.
+  @Input()
+  public showEditTime = true;
+  @Input()
+  public showExecutionTime = true;
+
   public sortMethod = SortMethod.EditTimeDesc;
 
   public lastSort(): void {

frontend/src/app/dashboard/component/user/user-dataset/user-dataset.component.html

@@ -32,26 +32,32 @@ <h2 class="page-title">Datasets</h2>
           nzTheme="outline"></i>
         <span>Create Dataset</span>
       </button>
-      <button
-        nz-button
-        title="List View"
-        (click)="setViewType('list')"
-        [nzType]="viewType === 'list' ? 'primary' : 'default'">
-        <i
-          nz-icon
-          nzType="bars"
-          nzTheme="outline"></i>
-      </button>
-      <button
-        nz-button
-        title="Card View"
-        (click)="setViewType('card')"
-        [nzType]="viewType === 'card' ? 'primary' : 'default'">
-        <i
-          nz-icon
-          nzType="appstore"
-          nzTheme="outline"></i>
-      </button>
+      <nz-space-compact class="utility-button-group">
+        <texera-sort-button
+          [showEditTime]="false"
+          [showExecutionTime]="false"
+          (sortMethodChange)="sortMethod = $event; search()"></texera-sort-button>
+        <button
+          nz-button
+          title="List View"
+          (click)="setViewType('list')"
+          [nzType]="viewType === 'list' ? 'primary' : 'default'">
+          <i
+            nz-icon
+            nzType="bars"
+            nzTheme="outline"></i>
+        </button>
+        <button
+          nz-button
+          title="Card View"
+          (click)="setViewType('card')"
+          [nzType]="viewType === 'card' ? 'primary' : 'default'">
+          <i
+            nz-icon
+            nzType="appstore"
+            nzTheme="outline"></i>
+        </button>
+      </nz-space-compact>
       <texera-filters #filters></texera-filters>
     </div>
   </nz-card>

frontend/src/app/dashboard/component/user/user-dataset/user-dataset.component.spec.ts

@@ -130,6 +130,13 @@ describe("UserDatasetComponent", () => {
     });
   });
 
+  describe("default sort", () => {
+    it("defaults to CreateTimeDesc so newest datasets appear first", () => {
+      // Datasets have no last-modified time, so EditTimeDesc would leave the sort key NULL.
+      expect(component.sortMethod).toBe(SortMethod.CreateTimeDesc);
+    });
+  });
+
   describe("ngAfterViewInit", () => {
     it("subscribes to userChanged and calls search on each emission", () => {
       const searchSpy = vi.spyOn(component, "search").mockResolvedValue();

frontend/src/app/dashboard/component/user/user-dataset/user-dataset.component.ts

@@ -28,6 +28,7 @@ import { DashboardEntry } from "../../../type/dashboard-entry";
 import { SearchResultsComponent } from "../search-results/search-results.component";
 import { CardItemComponent } from "../list-item/card-item/card-item.component";
 import { FiltersComponent } from "../filters/filters.component";
+import { SortButtonComponent } from "../sort-button/sort-button.component";
 import { firstValueFrom } from "rxjs";
 import { USER_DATASET } from "../../../../app-routing.constant";
 import { NzModalService } from "ng-zorro-antd/modal";
@@ -36,7 +37,7 @@ import { DashboardDataset } from "../../../type/dashboard-dataset.interface";
 import { NzMessageService } from "ng-zorro-antd/message";
 import { map, tap } from "rxjs/operators";
 import { NzCardComponent } from "ng-zorro-antd/card";
-import { NzSpaceCompactItemDirective } from "ng-zorro-antd/space";
+import { NzSpaceCompactItemDirective, NzSpaceCompactComponent } from "ng-zorro-antd/space";
 import { NzButtonComponent } from "ng-zorro-antd/button";
 import { NzWaveDirective } from "ng-zorro-antd/core/wave";
 import { ɵNzTransitionPatchDirective } from "ng-zorro-antd/core/transition-patch";
@@ -53,11 +54,13 @@ import { FormsModule } from "@angular/forms";
   imports: [
     NzCardComponent,
     NzSpaceCompactItemDirective,
+    NzSpaceCompactComponent,
     NzButtonComponent,
     NzWaveDirective,
     ɵNzTransitionPatchDirective,
     NzIconDirective,
     FiltersComponent,
+    SortButtonComponent,
     FiltersInstructionsComponent,
     NzSelectComponent,
     FormsModule,
@@ -67,7 +70,9 @@ import { FormsModule } from "@angular/forms";
 })
 export class UserDatasetComponent implements AfterViewInit {
   private static readonly VIEW_MODE_STORAGE_KEY = "texera.userDataset.viewMode";
-  public sortMethod = SortMethod.EditTimeDesc;
+  // Datasets have no "last modified" timestamp, so EditTimeDesc leaves the sort key NULL for every
+  // row and produces an undefined order. Default to CreateTimeDesc so newly created datasets appear first.
+  public sortMethod = SortMethod.CreateTimeDesc;
   lastSortMethod: SortMethod | null = null;
   public isLogin = this.userService.isLogin();
   public currentUid = this.userService.getCurrentUser()?.uid;

frontend/src/app/hub/component/hub-search-result/hub-search-result.component.html

@@ -20,7 +20,10 @@
 <div class="search-container">
   <div class="search-section">
     <div class="filter">
-      <texera-sort-button (sortMethodChange)="sortMethod = $event; search()"></texera-sort-button>
+      <texera-sort-button
+        [showEditTime]="searchType !== 'dataset'"
+        [showExecutionTime]="searchType !== 'dataset'"
+        (sortMethodChange)="sortMethod = $event; search()"></texera-sort-button>
       <texera-filters #filters></texera-filters>
       <div
         *ngIf="searchType === 'dataset'"

frontend/src/app/hub/component/hub-search-result/hub-search-result.component.ts

@@ -110,6 +110,9 @@ export class HubSearchResultComponent implements OnInit, AfterViewInit {
     const url = this.router.url;
     if (url.includes("dataset")) {
       this.searchType = "dataset";
+      // Datasets have no last-modified/execution time, so EditTimeDesc leaves the sort key NULL.
+      // Default to CreateTimeDesc so newly created datasets appear first.
+      this.sortMethod = SortMethod.CreateTimeDesc;
     } else if (url.includes("workflow")) {
       this.searchType = "workflow";
     }