feat(cdk/table): add optional footer to cdk-text-column/mat-text-column

Added two new inputs to CdkTextColumn:
`footerText` (string) and `footerTextTransform` (function), automatically
inherited by MatTextColumn.

If the table does not define a footer, the column footer will be ignored.

Additionally, TextColumnOptions includes a new default function called
`defaultFooterTextTransform`, used when neither `footerTextTransform` nor
`footerText` are provided.

Fixes #24532

src/cdk/table/text-column.spec.ts

@@ -16,7 +16,13 @@ describe('CdkTextColumn', () => {
 
   beforeEach(waitForAsync(() => {
     TestBed.configureTestingModule({
-      imports: [CdkTableModule, BasicTextColumnApp, MissingTableApp, TextColumnWithoutNameApp],
+      imports: [
+        CdkTableModule,
+        BasicTextColumnApp,
+        MissingTableApp,
+        TextColumnWithoutNameApp,
+        TextColumnWithFooter,
+      ],
     }).compileComponents();
   }));
 
@@ -148,12 +154,104 @@ describe('CdkTextColumn', () => {
       ]);
     });
   });
+
+  describe('with footer', () => {
+    const expectedDefaultTableHeaderAndData = [
+      ['PropertyA', 'PropertyB', 'PropertyC', 'PropertyD'],
+      ['Laptop', 'Electronics', 'New', '999.99'],
+      ['Charger', 'Accessories', 'Used', '49.99'],
+    ];
+
+    function createTestComponent(options: TextColumnOptions<any>) {
+      TestBed.resetTestingModule();
+      TestBed.configureTestingModule({
+        imports: [CdkTableModule, TextColumnWithFooter],
+        providers: [{provide: TEXT_COLUMN_OPTIONS, useValue: options}],
+      });
+
+      fixture = TestBed.createComponent(TextColumnWithFooter);
+      component = fixture.componentInstance;
+      fixture.detectChanges();
+
+      tableElement = fixture.nativeElement.querySelector('.cdk-table');
+    }
+
+    it('should be able to provide a default footer text transformation (function)', () => {
+      const expectedFooterPropertyA = 'propertyA!';
+      const expectedFooterPropertyB = 'propertyB!';
+      const expectedFooterPropertyC = '';
+      const expectedFooterPropertyD = '';
+      const defaultFooterTextTransform = (name: string) => `${name}!`;
+      createTestComponent({defaultFooterTextTransform});
+
+      expectTableToMatchContent(tableElement, [
+        ...expectedDefaultTableHeaderAndData,
+        [
+          expectedFooterPropertyA,
+          expectedFooterPropertyB,
+          expectedFooterPropertyC,
+          expectedFooterPropertyD,
+        ],
+      ]);
+    });
+
+    it('should be able to provide a footer text transformation (function)', () => {
+      createTestComponent({});
+      const expectedFooterPropertyA = '';
+      const expectedFooterPropertyB = '';
+      const expectedFooterPropertyC = '';
+      const expectedFooterPropertyD = '1049.98';
+      // footer text transformation function
+      component.getTotal = (): string => {
+        const total = component.data
+          .map(t => t.propertyD)
+          .reduce((acc, value) => (acc || 0) + (value || 0), 0);
+        return total ? total.toString() : '';
+      };
+
+      fixture.changeDetectorRef.markForCheck();
+      fixture.detectChanges();
+
+      expectTableToMatchContent(tableElement, [
+        ...expectedDefaultTableHeaderAndData,
+        [
+          expectedFooterPropertyA,
+          expectedFooterPropertyB,
+          expectedFooterPropertyC,
+          expectedFooterPropertyD,
+        ],
+      ]);
+    });
+
+    it('should be able to provide a plain footer text', () => {
+      createTestComponent({});
+      const expectedFooterPropertyA = '';
+      const expectedFooterPropertyB = '';
+      const expectedFooterPropertyC = 'Total';
+      const expectedFooterPropertyD = '';
+
+      component.footerTextPropertyC = 'Total';
+      fixture.changeDetectorRef.markForCheck();
+      fixture.detectChanges();
+
+      expectTableToMatchContent(tableElement, [
+        ...expectedDefaultTableHeaderAndData,
+        [
+          expectedFooterPropertyA,
+          expectedFooterPropertyB,
+          expectedFooterPropertyC,
+          expectedFooterPropertyD,
+        ],
+      ]);
+    });
+  });
 });
 
 interface TestData {
   propertyA: string;
   propertyB: string;
   propertyC: string;
+  propertyD?: number;
 }
 
 @Component({
@@ -179,8 +277,12 @@ class BasicTextColumnApp {
   ];
 
   headerTextB: string;
+  footerTextPropertyC: string = '';
   dataAccessorA: (data: TestData) => string;
-  justifyC = 'start';
+  justifyC: 'start' = 'start';
+  getTotal() {
+    return '';
+  }
 }
 
 @Component({
@@ -205,3 +307,27 @@ class MissingTableApp {}
   imports: [CdkTableModule],
 })
 class TextColumnWithoutNameApp extends BasicTextColumnApp {}
+
+@Component({
+  template: `
+    <cdk-table [dataSource]="data">
+      <cdk-text-column name="propertyA"/>
+      <cdk-text-column name="propertyB"/>
+      <cdk-text-column name="propertyC" [footerText]="footerTextPropertyC"/>
+      <cdk-text-column name="propertyD" [footerTextTransform]="getTotal"/>
+
+      <cdk-header-row *cdkHeaderRowDef="displayedColumns"/>
+      <cdk-row *cdkRowDef="let row; columns: displayedColumns"/>
+      <cdk-footer-row *cdkFooterRowDef="displayedColumns"/>
+    </cdk-table>
+  `,
+  standalone: true,
+  imports: [CdkTableModule],
+})
+class TextColumnWithFooter extends BasicTextColumnApp {
+  override displayedColumns = ['propertyA', 'propertyB', 'propertyC', 'propertyD'];
+  override data = [
+    {propertyA: 'Laptop', propertyB: 'Electronics', propertyC: 'New', propertyD: 999.99},
+    {propertyA: 'Charger', propertyB: 'Accessories', propertyC: 'Used', propertyD: 49.99},
+  ];
+}

src/cdk/table/text-column.ts

@@ -17,7 +17,15 @@ import {
   ViewChild,
   ViewEncapsulation,
 } from '@angular/core';
-import {CdkCellDef, CdkColumnDef, CdkHeaderCellDef, CdkHeaderCell, CdkCell} from './cell';
+import {
+  CdkCellDef,
+  CdkColumnDef,
+  CdkHeaderCellDef,
+  CdkHeaderCell,
+  CdkCell,
+  CdkFooterCellDef,
+  CdkFooterCell,
+} from './cell';
 import {CdkTable} from './table';
 import {
   getTableTextColumnMissingParentTableError,
@@ -26,13 +34,15 @@ import {
 import {TEXT_COLUMN_OPTIONS, TextColumnOptions} from './tokens';
 
 /**
- * Column that simply shows text content for the header and row cells. Assumes that the table
- * is using the native table implementation (`<table>`).
+ * Column that simply shows text content for the header, row cells, and optionally for the footer.
+ * Assumes that the table is using the native table implementation (`<table>`).
  *
  * By default, the name of this column will be the header text and data property accessor.
  * The header text can be overridden with the `headerText` input. Cell values can be overridden with
- * the `dataAccessor` input. Change the text justification to the start or end using the `justify`
- * input.
+ * the `dataAccessor` input. If the table has a footer definition, the default footer text for this
+ * column will be empty. The footer text can be overridden with the `footerText` or
+ * `footerDataAccessor` input. Change the text justification to the start or end using the
+ * `justify` input.
  */
 @Component({
   selector: 'cdk-text-column',
@@ -44,6 +54,9 @@ import {TEXT_COLUMN_OPTIONS, TextColumnOptions} from './tokens';
       <td cdk-cell *cdkCellDef="let data" [style.text-align]="justify">
         {{dataAccessor(data, name)}}
       </td>
+      <td cdk-footer-cell *cdkFooterCellDef [style.text-align]="justify">
+        {{footerTextTransform(name)}}
+      </td>
     </ng-container>
   `,
   encapsulation: ViewEncapsulation.None,
@@ -55,7 +68,15 @@ import {TEXT_COLUMN_OPTIONS, TextColumnOptions} from './tokens';
   // tslint:disable-next-line:validate-decorators
   changeDetection: ChangeDetectionStrategy.Default,
   standalone: true,
-  imports: [CdkColumnDef, CdkHeaderCellDef, CdkHeaderCell, CdkCellDef, CdkCell],
+  imports: [
+    CdkCell,
+    CdkCellDef,
+    CdkColumnDef,
+    CdkFooterCell,
+    CdkFooterCellDef,
+    CdkHeaderCell,
+    CdkHeaderCellDef,
+  ],
 })
 export class CdkTextColumn<T> implements OnDestroy, OnInit {
   /** Column name that should be used to reference this column. */
@@ -86,6 +107,20 @@ export class CdkTextColumn<T> implements OnDestroy, OnInit {
    */
   @Input() dataAccessor: (data: T, name: string) => string;
 
+  /**
+   * Text label that should be used for the column footer. If this property is not
+   * set, the footer won't be displayed unless `footerDataAccessor` is set.
+   */
+  @Input() footerText: string;
+
+  /**
+   * Footer data accessor function. If this property is set, it will take precedence over the
+   * footerText property. If footerText is set and footerDataAccessor is not, footerText will be
+   * used. If neither is set, and the table has a footer defined, the footer cells will render an
+   * empty string.
+   */
+  @Input() footerTextTransform: (name: string) => string;
+
   /** Alignment of the cell values. */
   @Input() justify: 'start' | 'end' | 'center' = 'start';
 
@@ -110,12 +145,18 @@ export class CdkTextColumn<T> implements OnDestroy, OnInit {
    */
   @ViewChild(CdkHeaderCellDef, {static: true}) headerCell: CdkHeaderCellDef;
 
+  /**
+   * The column footerCell is provided to the column during `ngOnInit` with a static query.
+   * @docs-private
+   */
+  @ViewChild(CdkFooterCellDef, {static: true}) footerCell: CdkFooterCellDef;
+
   constructor(
     // `CdkTextColumn` is always requiring a table, but we just assert it manually
     // for better error reporting.
     // tslint:disable-next-line: lightweight-tokens
-    @Optional() private _table: CdkTable<T>,
-    @Optional() @Inject(TEXT_COLUMN_OPTIONS) private _options: TextColumnOptions<T>,
+    @Optional() private readonly _table: CdkTable<T>,
+    @Optional() @Inject(TEXT_COLUMN_OPTIONS) private readonly _options: TextColumnOptions<T>,
   ) {
     this._options = _options || {};
   }
@@ -132,12 +173,15 @@ export class CdkTextColumn<T> implements OnDestroy, OnInit {
         this._options.defaultDataAccessor || ((data: T, name: string) => (data as any)[name]);
     }
 
+    this._defineFooterTextTransform();
+
     if (this._table) {
       // Provide the cell and headerCell directly to the table with the static `ViewChild` query,
       // since the columnDef will not pick up its content by the time the table finishes checking
       // its content and initializing the rows.
       this.columnDef.cell = this.cell;
       this.columnDef.headerCell = this.headerCell;
+      this.columnDef.footerCell = this.footerCell;
       this._table.addColumnDef(this.columnDef);
     } else if (typeof ngDevMode === 'undefined' || ngDevMode) {
       throw getTableTextColumnMissingParentTableError();
@@ -154,7 +198,7 @@ export class CdkTextColumn<T> implements OnDestroy, OnInit {
    * Creates a default header text. Use the options' header text transformation function if one
    * has been provided. Otherwise simply capitalize the column name.
    */
-  _createDefaultHeaderText() {
+  _createDefaultHeaderText(): string {
     const name = this.name;
 
     if (!name && (typeof ngDevMode === 'undefined' || ngDevMode)) {
@@ -169,9 +213,27 @@ export class CdkTextColumn<T> implements OnDestroy, OnInit {
   }
 
   /** Synchronizes the column definition name with the text column name. */
-  private _syncColumnDefName() {
+  private _syncColumnDefName(): void {
     if (this.columnDef) {
       this.columnDef.name = this.name;
     }
   }
+
+  /**
+   * Defines the function to transform the footer text for the column.
+   * If `footerTextTransform` is not set, it will:
+   * - Use `footerText` if defined, or
+   * - Use `defaultFooterTextTransform` from options, or
+   * - Default to an empty string.
+   */
+  private _defineFooterTextTransform(): void {
+    if (!this.footerTextTransform) {
+      // footerText can just be an empty string
+      if (this.footerText !== undefined) {
+        this.footerTextTransform = () => this.footerText;
+      } else {
+        this.footerTextTransform = this._options.defaultFooterTextTransform || (() => '');
+      }
+    }
+  }
 }

src/cdk/table/tokens.ts

@@ -24,6 +24,9 @@ export interface TextColumnOptions<T> {
 
   /** Default data accessor to use if one is not provided. */
   defaultDataAccessor?: (data: T, name: string) => string;
+
+  /** Default footer text transform to use if one is not provided. */
+  defaultFooterTextTransform?: (name: string) => string;
 }
 
 /** Injection token that can be used to specify the text column options. */

src/components-examples/material/table/index.ts

@@ -29,3 +29,4 @@ export {TableDynamicArrayDataExample} from './table-dynamic-array-data/table-dyn
 export {TableDynamicObservableDataExample} from './table-dynamic-observable-data/table-dynamic-observable-data-example';
 export {TableGeneratedColumnsExample} from './table-generated-columns/table-generated-columns-example';
 export {TableFlexLargeRowExample} from './table-flex-large-row/table-flex-large-row-example';
+export {TableTextColumnWithFooterExample} from './table-text-column-with-footer/table-text-column-with-footer-example';

src/components-examples/material/table/table-text-column-with-footer/table-text-column-with-footer-example.css

@@ -0,0 +1,3 @@
+table {
+  width: 100%;
+}

src/components-examples/material/table/table-text-column-with-footer/table-text-column-with-footer-example.html

@@ -0,0 +1,10 @@
+<table mat-table [dataSource]="dataSource" class="mat-elevation-z8">
+  <mat-text-column name="name" [footerText]="nameFooterText"></mat-text-column>
+  <mat-text-column name="price" [footerTextTransform]="getTotal" justify="end"></mat-text-column>
+  <mat-text-column name="insurance" [footerTextTransform]="getTotal" justify="end"></mat-text-column>
+  <mat-text-column name="category"></mat-text-column>
+
+  <tr mat-header-row *matHeaderRowDef="displayedColumns"></tr>
+  <tr mat-row *matRowDef="let row; columns: displayedColumns;"></tr>
+  <tr mat-footer-row *matFooterRowDef="displayedColumns"></tr>
+</table>

src/components-examples/material/table/table-text-column-with-footer/table-text-column-with-footer-example.ts

@@ -0,0 +1,47 @@
+import {Component} from '@angular/core';
+import {MatTableDataSource, MatTableModule} from '@angular/material/table';
+import {DecimalPipe} from '@angular/common';
+
+export interface Product {
+  name: string;
+  price: number;
+  insurance: number;
+  category: string;
+}
+
+const PRODUCT_DATA: Product[] = [
+  {name: 'Laptop', price: 999.99, insurance: 100.5, category: 'Electronics'},
+  {name: 'Phone', price: 699.99, insurance: 50.5, category: 'Electronics'},
+  {name: 'Tablet', price: 399.99, insurance: 25.5, category: 'Electronics'},
+  {name: 'Headphones', price: 199.99, insurance: 15, category: 'Accessories'},
+  {name: 'Charger', price: 49.99, insurance: 0, category: 'Accessories'},
+];
+
+/**
+ * @title Demonstrates the use of `mat-text-column` with footer cells. This example includes a fixed
+ * footer text for the 'name' column. The 'price' and 'insurance' columns use a text transformation
+ * function to determine their footer text. The 'category' column has a default empty footer text.
+ */
+@Component({
+  selector: 'table-text-column-with-footer-example',
+  styleUrl: 'table-text-column-with-footer-example.css',
+  templateUrl: 'table-text-column-with-footer-example.html',
+  standalone: true,
+  imports: [MatTableModule],
+})
+export class TableTextColumnWithFooterExample {
+  nameFooterText = 'Total';
+  displayedColumns: string[] = ['name', 'price', 'insurance', 'category'];
+  dataSource = new MatTableDataSource(PRODUCT_DATA);
+
+  decimalPipe = new DecimalPipe('en-US');
+
+  /** Function to sum the values of a given column.  */
+  getTotal = (column: string): string => {
+    const total = PRODUCT_DATA.map(t => t[column as keyof Product] as number).reduce(
+      (acc, value) => acc + value,
+      0,
+    );
+    return this.decimalPipe.transform(total, '1.2-2') || '';
+  };
+}