feat(selection-list): support specifying theme color

Currently the selection list always uses the `accent` color for the underlying
pseudo checkbox of list options. In order to make this configurable by the
user, we add a `color` input that matches our other usages of the `color`
input in order to be consistent.

Since we want to allow that a color can be specified for the `<mat-selection-list>` and
that it's possible to overwrite the color for an individual list option, we don't use the
color mixin as it brings in a lot of overhead and also doesn't make it easy to provide
the desired precedence for individual options. Also we **can't** set the color class
on the `<mat-selection-list>` as the pseudo checkbox will then ignore the color class
set for the individual list option.

Closes #15234

Author: devversion

src/dev-app/list/list-demo.html

@@ -120,13 +120,14 @@ <h2>Selection list</h2>
                         (ngModelChange)="onSelectedOptionsChange($event)"
                         (change)="changeEventCount = changeEventCount + 1"
                         [disabled]="selectionListDisabled"
-                        [disableRipple]="selectionListRippleDisabled">
+                        [disableRipple]="selectionListRippleDisabled"
+                        color="primary">
       <h3 mat-subheader>Groceries</h3>
 
       <mat-list-option value="bananas" checkboxPosition="before">Bananas</mat-list-option>
       <mat-list-option selected value="oranges">Oranges</mat-list-option>
-      <mat-list-option value="apples">Apples</mat-list-option>
-      <mat-list-option value="strawberries">Strawberries</mat-list-option>
+      <mat-list-option value="apples" color="accent">Apples</mat-list-option>
+      <mat-list-option value="strawberries" color="warn">Strawberries</mat-list-option>
     </mat-selection-list>
 
     <mat-selection-list [disableRipple]="selectionListRippleDisabled">

src/lib/list/selection-list.spec.ts

@@ -14,7 +14,7 @@ import {
   ViewChildren,
 } from '@angular/core';
 import {async, ComponentFixture, fakeAsync, TestBed, tick, flush} from '@angular/core/testing';
-import {MatRipple, defaultRippleAnimationConfig} from '@angular/material/core';
+import {MatRipple, defaultRippleAnimationConfig, ThemePalette} from '@angular/material/core';
 import {By} from '@angular/platform-browser';
 import {
   MatListModule,
@@ -123,6 +123,31 @@ describe('MatSelectionList without forms', () => {
       expect(listOptions[2].nativeElement.getAttribute('aria-disabled')).toBe('false');
     });
 
+    it('should be able to specify a color for list options', () => {
+      expect(listOptions.map(option => option.nativeElement)
+          .every(option => !option.classList.contains('mat-primary'))).toBe(true);
+      expect(listOptions.map(option => option.nativeElement)
+        .every(option => !option.classList.contains('mat-warn'))).toBe(true);
+
+      // All options will be set to the "warn" color.
+      fixture.componentInstance.selectionListColor = 'warn';
+      fixture.detectChanges();
+
+      expect(listOptions.map(option => option.nativeElement)
+        .every(option => !option.classList.contains('mat-primary'))).toBe(true);
+      expect(listOptions.map(option => option.nativeElement)
+        .every(option => option.classList.contains('mat-warn'))).toBe(true);
+
+      // Color will be set explicitly for an option and should take precedence.
+      fixture.componentInstance.firstOptionColor = 'primary';
+      fixture.detectChanges();
+
+      expect(listOptions[0].nativeElement.classList).toContain('mat-primary');
+      expect(listOptions[0].nativeElement.classList).not.toContain('mat-warn');
+      expect(listOptions.slice(1).map(option => option.nativeElement)
+        .every(option => option.classList.contains('mat-warn'))).toBe(true);
+    });
+
     it('should be able to deselect an option', () => {
       let testListItem = listOptions[2].injector.get<MatListOption>(MatListOption);
       let selectList =
@@ -1122,8 +1147,10 @@ describe('MatSelectionList with forms', () => {
   <mat-selection-list
     id="selection-list-1"
     (selectionChange)="onValueChange($event)"
-    [disableRipple]="listRippleDisabled">
-    <mat-list-option checkboxPosition="before" disabled="true" value="inbox">
+    [disableRipple]="listRippleDisabled"
+    [color]="selectionListColor">
+    <mat-list-option checkboxPosition="before" disabled="true" value="inbox"
+                     [color]="firstOptionColor">
       Inbox (disabled selection-option)
     </mat-list-option>
     <mat-list-option id="testSelect" checkboxPosition="before" class="test-native-focus"
@@ -1140,6 +1167,8 @@ describe('MatSelectionList with forms', () => {
 class SelectionListWithListOptions {
   showLastOption: boolean = true;
   listRippleDisabled = false;
+  selectionListColor: ThemePalette;
+  firstOptionColor: ThemePalette;
 
   onValueChange(_change: MatSelectionListChange) {}
 }

src/lib/list/selection-list.ts

@@ -46,6 +46,7 @@ import {
   MatLine,
   setLines,
   mixinDisableRipple,
+  ThemePalette,
 } from '@angular/material/core';
 import {ControlValueAccessor, NG_VALUE_ACCESSOR} from '@angular/forms';
 import {Subscription} from 'rxjs';
@@ -97,6 +98,11 @@ export class MatSelectionListChange {
     'tabindex': '-1',
     '[class.mat-list-item-disabled]': 'disabled',
     '[class.mat-list-item-with-avatar]': '_avatar || _icon',
+    // Manually set the "primary" or "warn" class if the color has been explicitly
+    // set to "primary" or "warn". The pseudo checkbox picks up these classes for
+    // its theme. The accent theme palette is the default and doesn't need to be set.
+    '[class.mat-primary]': 'color === "primary"',
+    '[class.mat-warn]': 'color === "warn"',
     '[attr.aria-selected]': 'selected.toString()',
     '[attr.aria-disabled]': 'disabled.toString()',
   },
@@ -121,6 +127,12 @@ export class MatListOption extends _MatListOptionMixinBase
   /** Whether the label should appear before or after the checkbox. Defaults to 'after' */
   @Input() checkboxPosition: 'before' | 'after' = 'after';
 
+  /** Theme color of the list option. This sets the color of the checkbox. */
+  @Input()
+  get color(): ThemePalette { return this._color || this.selectionList.color; }
+  set color(newValue: ThemePalette) { this._color = newValue; }
+  private _color: ThemePalette;
+
   /** Value of the option */
   @Input()
   get value(): any { return this._value; }
@@ -316,6 +328,9 @@ export class MatSelectionList extends _MatSelectionListMixinBase implements Focu
   /** Tabindex of the selection list. */
   @Input() tabIndex: number = 0;
 
+  /** Theme color of the selection list. This sets the checkbox color for all list options. */
+  @Input() color: ThemePalette = 'accent';
+
   /**
    * Function used for comparing an option against the selected value when determining which
    * options should appear as selected. The first argument is the value of an options. The second