feat(table): add the ability to show a data row when no data is avail…

…able (angular#18041)

As the table is set up at the moment, there's no convenient way to show the user something when their filtered table didn't match any data. These changes add a new directive that renders out a single row when no other data is available which can be used to show a message.

src/cdk/table/row.ts

@@ -306,3 +306,11 @@ export class CdkFooterRow {
 })
 export class CdkRow {
 }
+
+/** Row that can be used to display a message when no data is shown in the table. */
+@Directive({
+  selector: 'ng-template[cdkNoDataRow]'
+})
+export class CdkNoDataRow {
+  constructor(public templateRef: TemplateRef<any>) {}
+}

src/cdk/table/table-module.ts

@@ -7,10 +7,11 @@
  */
 
 import {NgModule} from '@angular/core';
-import {HeaderRowOutlet, DataRowOutlet, CdkTable, FooterRowOutlet} from './table';
+import {HeaderRowOutlet, DataRowOutlet, CdkTable, FooterRowOutlet, NoDataRowOutlet} from './table';
 import {
   CdkCellOutlet, CdkFooterRow, CdkFooterRowDef, CdkHeaderRow, CdkHeaderRowDef, CdkRow,
-  CdkRowDef
+  CdkRowDef,
+  CdkNoDataRow
 } from './row';
 import {
   CdkColumnDef, CdkHeaderCellDef, CdkHeaderCell, CdkCell, CdkCellDef,
@@ -38,6 +39,8 @@ const EXPORTED_DECLARATIONS = [
   HeaderRowOutlet,
   FooterRowOutlet,
   CdkTextColumn,
+  CdkNoDataRow,
+  NoDataRowOutlet,
 ];
 
 @NgModule({

src/cdk/table/table.spec.ts

@@ -285,6 +285,22 @@ describe('CdkTable', () => {
         ['Footer C', 'Footer B'],
       ]);
     });
+
+    it('should be able to show a message when no data is being displayed', () => {
+      expect(tableElement.textContent!.trim()).not.toContain('No data');
+
+      const originalData = dataSource.data;
+      dataSource.data = [];
+      fixture.detectChanges();
+
+      expect(tableElement.textContent!.trim()).toContain('No data');
+
+      dataSource.data = originalData;
+      fixture.detectChanges();
+
+      expect(tableElement.textContent!.trim()).not.toContain('No data');
+    });
+
   });
 
   it('should render no rows when the data is null', fakeAsync(() => {
@@ -513,6 +529,28 @@ describe('CdkTable', () => {
     expect(innerRows.map(row => row.cells.length)).toEqual([3, 3, 3]);
   });
 
+  it('should be able to show a message when no data is being displayed in a native table', () => {
+    const thisFixture = createComponent(NativeHtmlTableApp);
+    thisFixture.detectChanges();
+
+    // Assert that the data is inside the tbody specifically.
+    const tbody = thisFixture.nativeElement.querySelector('tbody');
+    const dataSource = thisFixture.componentInstance.dataSource!;
+    const originalData = dataSource.data;
+
+    expect(tbody.textContent!.trim()).not.toContain('No data');
+
+    dataSource.data = [];
+    thisFixture.detectChanges();
+
+    expect(tbody.textContent!.trim()).toContain('No data');
+
+    dataSource.data = originalData;
+    thisFixture.detectChanges();
+
+    expect(tbody.textContent!.trim()).not.toContain('No data');
+  });
+
   it('should apply correct roles for native table elements', () => {
     const thisFixture = createComponent(NativeHtmlTableApp);
     const thisTableElement: HTMLTableElement = thisFixture.nativeElement.querySelector('table');
@@ -1490,6 +1528,8 @@ class BooleanDataSource extends DataSource<boolean> {
                *cdkRowDef="let row; columns: columnsToRender"></cdk-row>
       <cdk-footer-row class="customFooterRowClass"
                       *cdkFooterRowDef="columnsToRender"></cdk-footer-row>
+
+      <div *cdkNoDataRow>No data</div>
     </cdk-table>
   `
 })
@@ -2297,6 +2337,9 @@ class OuterTableApp {
 
       <tr cdk-header-row *cdkHeaderRowDef="columnsToRender"></tr>
       <tr cdk-row *cdkRowDef="let row; columns: columnsToRender" class="customRowClass"></tr>
+      <tr *cdkNoDataRow>
+        <td>No data</td>
+      </tr>
     </table>
   `
 })

src/cdk/table/table.ts

@@ -35,7 +35,8 @@ import {
   TrackByFunction,
   ViewChild,
   ViewContainerRef,
-  ViewEncapsulation
+  ViewEncapsulation,
+  ContentChild
 } from '@angular/core';
 import {
   BehaviorSubject,
@@ -54,7 +55,8 @@ import {
   CdkCellOutletRowContext,
   CdkFooterRowDef,
   CdkHeaderRowDef,
-  CdkRowDef
+  CdkRowDef,
+  CdkNoDataRow
 } from './row';
 import {StickyStyler} from './sticky-styler';
 import {
@@ -106,6 +108,16 @@ export class FooterRowOutlet implements RowOutlet {
   constructor(public viewContainer: ViewContainerRef, public elementRef: ElementRef) {}
 }
 
+/**
+ * Provides a handle for the table to grab the view
+ * container's ng-container to insert the no data row.
+ * @docs-private
+ */
+@Directive({selector: '[noDataRowOutlet]'})
+export class NoDataRowOutlet implements RowOutlet {
+  constructor(public viewContainer: ViewContainerRef, public elementRef: ElementRef) {}
+}
+
 /**
  * The table template that can be used by the mat-table. Should not be used outside of the
  * material library.
@@ -119,6 +131,7 @@ export const CDK_TABLE_TEMPLATE =
   <ng-content select="colgroup, col"></ng-content>
   <ng-container headerRowOutlet></ng-container>
   <ng-container rowOutlet></ng-container>
+  <ng-container noDataRowOutlet></ng-container>
   <ng-container footerRowOutlet></ng-container>
 `;
 
@@ -293,6 +306,9 @@ export class CdkTable<T> implements AfterContentChecked, CollectionViewer, OnDes
    */
   protected stickyCssClass: string = 'cdk-table-sticky';
 
+  /** Whether the no data row is currently showing anything. */
+  private _isShowingNoDataRow = false;
+
   /**
    * Tracking function that will be used to check the differences in data changes. Used similarly
    * to `ngFor` `trackBy` function. Optimize row operations by identifying a row based on its data
@@ -379,6 +395,7 @@ export class CdkTable<T> implements AfterContentChecked, CollectionViewer, OnDes
   @ViewChild(DataRowOutlet, {static: true}) _rowOutlet: DataRowOutlet;
   @ViewChild(HeaderRowOutlet, {static: true}) _headerRowOutlet: HeaderRowOutlet;
   @ViewChild(FooterRowOutlet, {static: true}) _footerRowOutlet: FooterRowOutlet;
+  @ViewChild(NoDataRowOutlet, {static: true}) _noDataRowOutlet: NoDataRowOutlet;
 
   /**
    * The column definitions provided by the user that contain what the header, data, and footer
@@ -399,6 +416,9 @@ export class CdkTable<T> implements AfterContentChecked, CollectionViewer, OnDes
     descendants: true
   }) _contentFooterRowDefs: QueryList<CdkFooterRowDef>;
 
+  /** Row definition that will only be rendered if there's no data in the table. */
+  @ContentChild(CdkNoDataRow) _noDataRow: CdkNoDataRow;
+
   constructor(
       protected readonly _differs: IterableDiffers,
       protected readonly _changeDetectorRef: ChangeDetectorRef,
@@ -464,6 +484,7 @@ export class CdkTable<T> implements AfterContentChecked, CollectionViewer, OnDes
 
   ngOnDestroy() {
     this._rowOutlet.viewContainer.clear();
+    this._noDataRowOutlet.viewContainer.clear();
     this._headerRowOutlet.viewContainer.clear();
     this._footerRowOutlet.viewContainer.clear();
 
@@ -519,6 +540,7 @@ export class CdkTable<T> implements AfterContentChecked, CollectionViewer, OnDes
       rowView.context.$implicit = record.item.data;
     });
 
+    this._updateNoDataRow();
     this.updateStickyColumnStyles();
   }
 
@@ -1017,15 +1039,19 @@ export class CdkTable<T> implements AfterContentChecked, CollectionViewer, OnDes
   private _applyNativeTableSections() {
     const documentFragment = this._document.createDocumentFragment();
     const sections = [
-      {tag: 'thead', outlet: this._headerRowOutlet},
-      {tag: 'tbody', outlet: this._rowOutlet},
-      {tag: 'tfoot', outlet: this._footerRowOutlet},
+      {tag: 'thead', outlets: [this._headerRowOutlet]},
+      {tag: 'tbody', outlets: [this._rowOutlet, this._noDataRowOutlet]},
+      {tag: 'tfoot', outlets: [this._footerRowOutlet]},
     ];
 
     for (const section of sections) {
       const element = this._document.createElement(section.tag);
       element.setAttribute('role', 'rowgroup');
-      element.appendChild(section.outlet.elementRef.nativeElement);
+
+      for (const outlet of section.outlets) {
+        element.appendChild(outlet.elementRef.nativeElement);
+      }
+
       documentFragment.appendChild(element);
     }
 
@@ -1094,6 +1120,19 @@ export class CdkTable<T> implements AfterContentChecked, CollectionViewer, OnDes
     return items.filter(item => !item._table || item._table === this);
   }
 
+  /** Creates or removes the no data row, depending on whether any data is being shown. */
+  private _updateNoDataRow() {
+    if (this._noDataRow) {
+      const shouldShow = this._rowOutlet.viewContainer.length === 0;
+
+      if (shouldShow !== this._isShowingNoDataRow) {
+        const container = this._noDataRowOutlet.viewContainer;
+        shouldShow ? container.createEmbeddedView(this._noDataRow.templateRef) : container.clear();
+        this._isShowingNoDataRow = shouldShow;
+      }
+    }
+  }
+
   static ngAcceptInputType_multiTemplateDataRows: BooleanInput;
 }
 

src/components-examples/material/table/table-filtering/table-filtering-example.html

@@ -1,6 +1,6 @@
 <mat-form-field>
   <mat-label>Filter</mat-label>
-  <input matInput (keyup)="applyFilter($event)" placeholder="Ex. ium">
+  <input matInput (keyup)="applyFilter($event)" placeholder="Ex. ium" #input>
 </mat-form-field>
 
 <table mat-table [dataSource]="dataSource" class="mat-elevation-z8">
@@ -31,4 +31,9 @@
 
   <tr mat-header-row *matHeaderRowDef="displayedColumns"></tr>
   <tr mat-row *matRowDef="let row; columns: displayedColumns;"></tr>
+
+  <!-- Row shown when there is no matching data. -->
+  <tr class="mat-row" *matNoDataRow>
+    <td class="mat-cell" colspan="4">No data matching the filter "{{input.value}}"</td>
+  </tr>
 </table>

src/components-examples/material/table/table-overview/table-overview-example.html

@@ -1,6 +1,6 @@
 <mat-form-field>
   <mat-label>Filter</mat-label>
-  <input matInput (keyup)="applyFilter($event)" placeholder="Ex. Mia">
+  <input matInput (keyup)="applyFilter($event)" placeholder="Ex. Mia" #input>
 </mat-form-field>
 
 <div class="mat-elevation-z8">
@@ -31,7 +31,11 @@
     </ng-container>
 
     <tr mat-header-row *matHeaderRowDef="displayedColumns"></tr>
-    <tr mat-row *matRowDef="let row; columns: displayedColumns;">
+    <tr mat-row *matRowDef="let row; columns: displayedColumns;"></tr>
+
+    <!-- Row shown when there is no matching data. -->
+    <tr class="mat-row" *matNoDataRow>
+      <td class="mat-cell" colspan="4">No data matching the filter "{{input.value}}"</td>
     </tr>
   </table>
 

src/material-experimental/mdc-table/module.ts

@@ -25,7 +25,8 @@ import {
   MatHeaderRow,
   MatHeaderRowDef,
   MatRow,
-  MatRowDef
+  MatRowDef,
+  MatNoDataRow
 } from './row';
 
 const EXPORTED_DECLARATIONS = [
@@ -50,6 +51,7 @@ const EXPORTED_DECLARATIONS = [
   MatHeaderRow,
   MatRow,
   MatFooterRow,
+  MatNoDataRow,
 ];
 
 @NgModule({

src/material-experimental/mdc-table/row.ts

@@ -14,7 +14,8 @@ import {
   CdkHeaderRow,
   CdkHeaderRowDef,
   CdkRow,
-  CdkRowDef
+  CdkRowDef,
+  CdkNoDataRow
 } from '@angular/cdk/table';
 import {ChangeDetectionStrategy, Component, Directive, ViewEncapsulation} from '@angular/core';
 
@@ -110,3 +111,11 @@ export class MatFooterRow extends CdkFooterRow {
 })
 export class MatRow extends CdkRow {
 }
+
+/** Row that can be used to display a message when no data is shown in the table. */
+@Directive({
+  selector: 'ng-template[matNoDataRow]',
+  providers: [{provide: CdkNoDataRow, useExisting: MatNoDataRow}],
+})
+export class MatNoDataRow extends CdkNoDataRow {
+}

src/material-experimental/mdc-table/table.spec.ts

@@ -96,6 +96,27 @@ describe('MDC-based MatTable', () => {
       expect(innerRows.map(row => row.cells.length)).toEqual([3, 3, 3, 3]);
     });
 
+    it('should be able to show a message when no data is being displayed', () => {
+      const fixture = TestBed.createComponent(MatTableApp);
+      fixture.detectChanges();
+
+      // Assert that the data is inside the tbody specifically.
+      const tbody = fixture.nativeElement.querySelector('tbody')!;
+      const initialData = fixture.componentInstance.dataSource!.data;
+
+      expect(tbody.textContent.trim()).not.toContain('No data');
+
+      fixture.componentInstance.dataSource!.data = [];
+      fixture.detectChanges();
+
+      expect(tbody.textContent.trim()).toContain('No data');
+
+      fixture.componentInstance.dataSource!.data = initialData;
+      fixture.detectChanges();
+
+      expect(tbody.textContent.trim()).not.toContain('No data');
+    });
+
   });
 
   it('should render with MatTableDataSource and sort', () => {
@@ -555,6 +576,9 @@ class FakeDataSource extends DataSource<TestData> {
       <tr mat-header-row *matHeaderRowDef="columnsToRender"></tr>
       <tr mat-row *matRowDef="let row; columns: columnsToRender"></tr>
       <tr mat-row *matRowDef="let row; columns: ['special_column']; when: isFourthRow"></tr>
+      <tr *matNoDataRow>
+        <td>No data</td>
+      </tr>
       <tr mat-footer-row *matFooterRowDef="columnsToRender"></tr>
     </table>
   `

src/material/table/row.ts

@@ -14,7 +14,8 @@ import {
   CdkHeaderRow,
   CdkHeaderRowDef,
   CdkRow,
-  CdkRowDef
+  CdkRowDef,
+  CdkNoDataRow
 } from '@angular/cdk/table';
 import {ChangeDetectionStrategy, Component, Directive, ViewEncapsulation} from '@angular/core';
 
@@ -110,3 +111,11 @@ export class MatFooterRow extends CdkFooterRow {
 })
 export class MatRow extends CdkRow {
 }
+
+/** Row that can be used to display a message when no data is shown in the table. */
+@Directive({
+  selector: 'ng-template[matNoDataRow]',
+  providers: [{provide: CdkNoDataRow, useExisting: MatNoDataRow}],
+})
+export class MatNoDataRow extends CdkNoDataRow {
+}

src/material/table/table-module.ts

@@ -24,7 +24,8 @@ import {
   MatHeaderRow,
   MatHeaderRowDef,
   MatRow,
-  MatRowDef
+  MatRowDef,
+  MatNoDataRow
 } from './row';
 import {MatTextColumn} from './text-column';
 import {MatCommonModule} from '@angular/material/core';
@@ -51,6 +52,7 @@ const EXPORTED_DECLARATIONS = [
   MatHeaderRow,
   MatRow,
   MatFooterRow,
+  MatNoDataRow,
 
   MatTextColumn,
 ];