fix(list): add command+A for MacOs "select all" functionality.

packages/mdc-list/foundation.ts

@@ -413,7 +413,7 @@ export class MDCListFoundation extends MDCFoundation<MDCListAdapter> {
       this.toggleCheckboxRange(
           currentIndex, this.adapter.getListItemCount() - 1, currentIndex);
     } else if (
-        isLetterA && eventHasModifiers(['Control']) && this.isCheckboxList) {
+        isLetterA && (eventHasModifiers(['Control']) || eventHasModifiers(['Meta'])) && this.isCheckboxList) {
       event.preventDefault();
       this.checkboxListToggleAll(
           this.selectedIndex === numbers.UNSET_INDEX ?

packages/mdc-list/test/foundation.test.ts

@@ -1371,6 +1371,164 @@ describe('MDCListFoundation', () => {
            .toHaveBeenCalledWith(2, true);
      });
 
+  it('#handleKeydown should select all items on command(metaKey) + A, if nothing is selected',
+      () => {
+        const {foundation, mockAdapter} = setupTest();
+        const event = createMockKeyboardEvent('A', ['Meta']);
+
+        mockAdapter.hasCheckboxAtIndex.withArgs(0).and.returnValue(true);
+        mockAdapter.getListItemCount.and.returnValue(3);
+        foundation.layout();
+        foundation.handleKeydown(event, false, -1);
+
+        expect(event.preventDefault).toHaveBeenCalledTimes(1);
+        expect(mockAdapter.setCheckedCheckboxOrRadioAtIndex)
+            .toHaveBeenCalledTimes(3);
+        expect(mockAdapter.setCheckedCheckboxOrRadioAtIndex)
+            .toHaveBeenCalledWith(0, true);
+        expect(mockAdapter.setCheckedCheckboxOrRadioAtIndex)
+            .toHaveBeenCalledWith(1, true);
+        expect(mockAdapter.setCheckedCheckboxOrRadioAtIndex)
+            .toHaveBeenCalledWith(2, true);
+      });
+
+  it('#handleKeydown should select all items on command(metaKey) + lowercase A, if nothing is selected',
+      () => {
+        const {foundation, mockAdapter} = setupTest();
+        const event = createMockKeyboardEvent('a', ['Meta']);
+
+        mockAdapter.hasCheckboxAtIndex.withArgs(0).and.returnValue(true);
+        mockAdapter.getListItemCount.and.returnValue(3);
+        foundation.layout();
+        foundation.handleKeydown(event, false, -1);
+
+        expect(event.preventDefault).toHaveBeenCalledTimes(1);
+        expect(mockAdapter.setCheckedCheckboxOrRadioAtIndex)
+            .toHaveBeenCalledTimes(3);
+        expect(mockAdapter.setCheckedCheckboxOrRadioAtIndex)
+            .toHaveBeenCalledWith(0, true);
+        expect(mockAdapter.setCheckedCheckboxOrRadioAtIndex)
+            .toHaveBeenCalledWith(1, true);
+        expect(mockAdapter.setCheckedCheckboxOrRadioAtIndex)
+            .toHaveBeenCalledWith(2, true);
+      });
+
+  it('#handleKeydown should select all items on command(metaKey) + A, if some items are selected',
+      () => {
+        const {foundation, mockAdapter} = setupTest();
+        const event = createMockKeyboardEvent('A', ['Meta']);
+
+        mockAdapter.hasCheckboxAtIndex.withArgs(0).and.returnValue(true);
+        mockAdapter.getListItemCount.and.returnValue(4);
+        foundation.layout();
+        foundation.setSelectedIndex([1, 2]);
+
+        // Reset the calls since `setSelectedIndex` will throw it off.
+        mockAdapter.setCheckedCheckboxOrRadioAtIndex.calls.reset();
+        foundation.handleKeydown(event, false, -1);
+
+        expect(event.preventDefault).toHaveBeenCalledTimes(1);
+        expect(mockAdapter.setCheckedCheckboxOrRadioAtIndex)
+            .toHaveBeenCalledTimes(4);
+        expect(mockAdapter.setCheckedCheckboxOrRadioAtIndex)
+            .toHaveBeenCalledWith(0, true);
+        expect(mockAdapter.setCheckedCheckboxOrRadioAtIndex)
+            .toHaveBeenCalledWith(1, true);
+        expect(mockAdapter.setCheckedCheckboxOrRadioAtIndex)
+            .toHaveBeenCalledWith(2, true);
+        expect(mockAdapter.setCheckedCheckboxOrRadioAtIndex)
+            .toHaveBeenCalledWith(3, true);
+      });
+
+  it('#handleKeydown should deselect all items on command(metaKey) + A, if all items are selected',
+      () => {
+        const {foundation, mockAdapter} = setupTest();
+        const event = createMockKeyboardEvent('A', ['Meta']);
+
+        mockAdapter.hasCheckboxAtIndex.withArgs(0).and.returnValue(true);
+        mockAdapter.getListItemCount.and.returnValue(3);
+        foundation.layout();
+        foundation.setSelectedIndex([0, 1, 2]);
+
+        // Reset the calls since `setSelectedIndex` will throw it off.
+        mockAdapter.setCheckedCheckboxOrRadioAtIndex.calls.reset();
+        foundation.handleKeydown(event, false, -1);
+
+        expect(event.preventDefault).toHaveBeenCalledTimes(1);
+        expect(mockAdapter.setCheckedCheckboxOrRadioAtIndex)
+            .toHaveBeenCalledTimes(3);
+        expect(mockAdapter.setCheckedCheckboxOrRadioAtIndex)
+            .toHaveBeenCalledWith(0, false);
+        expect(mockAdapter.setCheckedCheckboxOrRadioAtIndex)
+            .toHaveBeenCalledWith(1, false);
+        expect(mockAdapter.setCheckedCheckboxOrRadioAtIndex)
+            .toHaveBeenCalledWith(2, false);
+      });
+
+  it('#handleKeydown should not select disabled items on command(metaKey) + A', () => {
+    const {foundation, mockAdapter} = setupTest();
+    const event = createMockKeyboardEvent('A', ['Meta']);
+
+    mockAdapter.hasCheckboxAtIndex.withArgs(0).and.returnValue(true);
+    mockAdapter.listItemAtIndexHasClass
+        .withArgs(1, cssClasses.LIST_ITEM_DISABLED_CLASS)
+        .and.returnValue(true);
+    mockAdapter.getListItemCount.and.returnValue(3);
+    foundation.layout();
+    foundation.handleKeydown(event, false, -1);
+
+    expect(event.preventDefault).toHaveBeenCalledTimes(1);
+    expect(mockAdapter.setCheckedCheckboxOrRadioAtIndex)
+        .toHaveBeenCalledTimes(3);
+    expect(mockAdapter.setCheckedCheckboxOrRadioAtIndex)
+        .toHaveBeenCalledWith(0, true);
+    expect(mockAdapter.setCheckedCheckboxOrRadioAtIndex)
+        .toHaveBeenCalledWith(1, false);
+    expect(mockAdapter.setCheckedCheckboxOrRadioAtIndex)
+        .toHaveBeenCalledWith(2, true);
+  });
+
+  it('#handleKeydown should not handle command(metaKey) + A on a non-checkbox list', () => {
+    const {foundation, mockAdapter} = setupTest();
+    const event = createMockKeyboardEvent('a', ['Meta']);
+
+    mockAdapter.hasCheckboxAtIndex.withArgs(0).and.returnValue(false);
+    mockAdapter.getListItemCount.and.returnValue(3);
+    foundation.layout();
+    foundation.handleKeydown(event, false, -1);
+
+    expect(event.preventDefault).not.toHaveBeenCalled();
+    expect(mockAdapter.setCheckedCheckboxOrRadioAtIndex).not.toHaveBeenCalled();
+  });
+
+  it('#handleKeydown should not deselect a selected disabled item on command(metaKey) + A',
+      () => {
+        const {foundation, mockAdapter} = setupTest();
+        const event = createMockKeyboardEvent('A', ['Meta']);
+
+        mockAdapter.hasCheckboxAtIndex.withArgs(0).and.returnValue(true);
+        mockAdapter.listItemAtIndexHasClass
+            .withArgs(1, cssClasses.LIST_ITEM_DISABLED_CLASS)
+            .and.returnValue(true);
+        mockAdapter.getListItemCount.and.returnValue(3);
+        foundation.layout();
+        foundation.setSelectedIndex([1]);
+
+        // Reset the calls since `setSelectedIndex` will throw it off.
+        mockAdapter.setCheckedCheckboxOrRadioAtIndex.calls.reset();
+        foundation.handleKeydown(event, false, -1);
+
+        expect(event.preventDefault).toHaveBeenCalledTimes(1);
+        expect(mockAdapter.setCheckedCheckboxOrRadioAtIndex)
+            .toHaveBeenCalledTimes(3);
+        expect(mockAdapter.setCheckedCheckboxOrRadioAtIndex)
+            .toHaveBeenCalledWith(0, true);
+        expect(mockAdapter.setCheckedCheckboxOrRadioAtIndex)
+            .toHaveBeenCalledWith(1, true);
+        expect(mockAdapter.setCheckedCheckboxOrRadioAtIndex)
+            .toHaveBeenCalledWith(2, true);
+      });
+
   it('#focusNextElement retains the focus on last item when wrapFocus=false and returns that index',
      () => {
        const {foundation, mockAdapter} = setupTest();