fix(badge): allow more data types for badge content (#20331)

Currently the badge's content is limited to `string` which excludes other legitimate use cases like numbers. These changes turn it into an `string | number | undefined | null` since we aren't actually doing anything with the value, apart from forwarding it.

Fixes #20326.

Author: crisbeto

src/material/badge/badge.spec.ts

@@ -27,15 +27,34 @@ describe('MatBadge', () => {
   }));
 
   it('should update the badge based on attribute', () => {
-    let badgeContentDebugElement = badgeNativeElement.querySelector('.mat-badge-content')!;
-
-    expect(badgeContentDebugElement.textContent).toContain('1');
+    const badgeElement = badgeNativeElement.querySelector('.mat-badge-content')!;
+    expect(badgeElement.textContent).toContain('1');
 
     testComponent.badgeContent = '22';
     fixture.detectChanges();
+    expect(badgeElement.textContent).toContain('22');
+  });
+
+  it('should be able to pass in falsy values to the badge content', () => {
+    const badgeElement = badgeNativeElement.querySelector('.mat-badge-content')!;
+    expect(badgeElement.textContent).toContain('1');
+
+    testComponent.badgeContent = 0;
+    fixture.detectChanges();
+    expect(badgeElement.textContent).toContain('0');
+  });
+
+  it('should treat null and undefined as empty strings in the badge content', () => {
+    const badgeElement = badgeNativeElement.querySelector('.mat-badge-content')!;
+    expect(badgeElement.textContent).toContain('1');
 
-    badgeContentDebugElement = badgeNativeElement.querySelector('.mat-badge-content')!;
-    expect(badgeContentDebugElement.textContent).toContain('22');
+    testComponent.badgeContent = null;
+    fixture.detectChanges();
+    expect(badgeElement.textContent?.trim()).toBe('');
+
+    testComponent.badgeContent = undefined;
+    fixture.detectChanges();
+    expect(badgeElement.textContent?.trim()).toBe('');
   });
 
   it('should apply class based on color attribute', () => {
@@ -234,7 +253,7 @@ describe('MatBadge', () => {
 class BadgeTestApp {
   @ViewChild(MatBadge) badgeInstance: MatBadge;
   badgeColor: ThemePalette;
-  badgeContent: string | number = '1';
+  badgeContent: string | number | undefined | null = '1';
   badgeDirection = 'above after';
   badgeHidden = false;
   badgeSize = 'medium';

src/material/badge/badge.ts

@@ -88,7 +88,7 @@ export class MatBadge extends _MatBadgeMixinBase implements OnDestroy, OnChanges
   @Input('matBadgePosition') position: MatBadgePosition = 'above after';
 
   /** The content for the badge */
-  @Input('matBadge') content: string;
+  @Input('matBadge') content: string | number | undefined | null;
 
   /** Message used to describe the decorated element via aria-describedby */
   @Input('matBadgeDescription')
@@ -188,7 +188,7 @@ export class MatBadge extends _MatBadgeMixinBase implements OnDestroy, OnChanges
     if (!this._badgeElement) {
       this._badgeElement = this._createBadgeElement();
     } else {
-      this._badgeElement.textContent = this.content;
+      this._badgeElement.textContent = this._stringifyContent();
     }
     return this._badgeElement;
   }
@@ -203,7 +203,7 @@ export class MatBadge extends _MatBadgeMixinBase implements OnDestroy, OnChanges
     this._clearExistingBadges(contentClass);
     badgeElement.setAttribute('id', `mat-badge-content-${this._id}`);
     badgeElement.classList.add(contentClass);
-    badgeElement.textContent = this.content;
+    badgeElement.textContent = this._stringifyContent();
 
     if (this._animationMode === 'NoopAnimations') {
       badgeElement.classList.add('_mat-animation-noopable');
@@ -246,11 +246,12 @@ export class MatBadge extends _MatBadgeMixinBase implements OnDestroy, OnChanges
   /** Adds css theme class given the color to the component host */
   private _setColor(colorPalette: ThemePalette) {
     if (colorPalette !== this._color) {
+      const classList = this._elementRef.nativeElement.classList;
       if (this._color) {
-        this._elementRef.nativeElement.classList.remove(`mat-badge-${this._color}`);
+        classList.remove(`mat-badge-${this._color}`);
       }
       if (colorPalette) {
-        this._elementRef.nativeElement.classList.add(`mat-badge-${colorPalette}`);
+        classList.add(`mat-badge-${colorPalette}`);
       }
     }
   }
@@ -270,6 +271,14 @@ export class MatBadge extends _MatBadgeMixinBase implements OnDestroy, OnChanges
     }
   }
 
+  /** Gets the string representation of the badge content. */
+  private _stringifyContent(): string {
+    // Convert null and undefined to an empty string which is consistent
+    // with how Angular handles them in inside template interpolations.
+    const content = this.content;
+    return content == null ? '' : `${content}`;
+  }
+
   static ngAcceptInputType_disabled: BooleanInput;
   static ngAcceptInputType_hidden: BooleanInput;
   static ngAcceptInputType_overlap: BooleanInput;

tools/public_api_guard/material/badge.d.ts

@@ -3,7 +3,7 @@ export declare class MatBadge extends _MatBadgeMixinBase implements OnDestroy, O
     _id: number;
     get color(): ThemePalette;
     set color(value: ThemePalette);
-    content: string;
+    content: string | number | undefined | null;
     get description(): string;
     set description(newDescription: string);
     get hidden(): boolean;