fix (dropdown): tolerate dropdowns without menus

src/components/dropdown/dropdown.test.ts

@@ -142,4 +142,180 @@ describe('<sl-dropdown>', () => {
     expect(afterHideHandler).to.have.been.calledOnce;
     expect(panel.hidden).to.be.true;
   });
+
+  it('should still open on arrow navigation when no menu items', async () => {
+    const el = await fixture<SlDropdown>(html`
+      <sl-dropdown>
+        <sl-button slot="trigger" caret>Toggle</sl-button>
+        <sl-menu> </sl-menu>
+      </sl-dropdown>
+    `);
+    const trigger = el.shadowRoot!.querySelector<HTMLElement>('[part="trigger"]')!;
+
+    trigger.dispatchEvent(
+      new KeyboardEvent('keydown', {
+        key: 'ArrowDown'
+      })
+    );
+
+    await el.updateComplete;
+
+    expect(el.open).to.be.true;
+  });
+
+  it('should open on arrow navigation', async () => {
+    const el = await fixture<SlDropdown>(html`
+      <sl-dropdown>
+        <sl-button slot="trigger" caret>Toggle</sl-button>
+        <sl-menu>
+          <sl-menu-item>Item 1</sl-menu-item>
+          <sl-menu-item>Item 2</sl-menu-item>
+        </sl-menu>
+      </sl-dropdown>
+    `);
+    const trigger = el.shadowRoot!.querySelector<HTMLElement>('[part="trigger"]')!;
+
+    trigger.dispatchEvent(
+      new KeyboardEvent('keydown', {
+        key: 'ArrowDown'
+      })
+    );
+
+    await el.updateComplete;
+
+    expect(el.open).to.be.true;
+  });
+
+  it('should close on escape key', async () => {
+    const el = await fixture<SlDropdown>(html`
+      <sl-dropdown open>
+        <sl-button slot="trigger" caret>Toggle</sl-button>
+        <sl-menu>
+          <sl-menu-item>Item 1</sl-menu-item>
+          <sl-menu-item>Item 2</sl-menu-item>
+        </sl-menu>
+      </sl-dropdown>
+    `);
+    const trigger = el.shadowRoot!.querySelector<HTMLElement>('[part="trigger"]')!;
+
+    trigger.dispatchEvent(
+      new KeyboardEvent('keydown', {
+        key: 'Escape'
+      })
+    );
+
+    await el.updateComplete;
+
+    expect(el.open).to.be.false;
+  });
+
+  it('should not open on arrow navigation when no menu exists', async () => {
+    const el = await fixture<SlDropdown>(html`
+      <sl-dropdown>
+        <sl-button slot="trigger" caret>Toggle</sl-button>
+        <div>Some custom content</div>
+      </sl-dropdown>
+    `);
+    const trigger = el.shadowRoot!.querySelector<HTMLElement>('[part="trigger"]')!;
+
+    trigger.dispatchEvent(
+      new KeyboardEvent('keydown', {
+        key: 'ArrowDown'
+      })
+    );
+
+    await el.updateComplete;
+
+    expect(el.open).to.be.false;
+  });
+
+  it('should open on enter key', async () => {
+    const el = await fixture<SlDropdown>(html`
+      <sl-dropdown>
+        <sl-button slot="trigger" caret>Toggle</sl-button>
+        <sl-menu>
+          <sl-menu-item>Item 1</sl-menu-item>
+        </sl-menu>
+      </sl-dropdown>
+    `);
+    const trigger = el.shadowRoot!.querySelector<HTMLElement>('[part="trigger"]')!;
+
+    trigger.dispatchEvent(
+      new KeyboardEvent('keydown', {
+        key: 'Enter'
+      })
+    );
+
+    await el.updateComplete;
+
+    expect(el.open).to.be.true;
+  });
+
+  it('should open on enter key when no menu exists', async () => {
+    const el = await fixture<SlDropdown>(html`
+      <sl-dropdown>
+        <sl-button slot="trigger" caret>Toggle</sl-button>
+        <div>Some custom content</div>
+      </sl-dropdown>
+    `);
+    const trigger = el.shadowRoot!.querySelector<HTMLElement>('[part="trigger"]')!;
+
+    trigger.dispatchEvent(
+      new KeyboardEvent('keydown', {
+        key: 'Enter'
+      })
+    );
+
+    await el.updateComplete;
+
+    expect(el.open).to.be.true;
+  });
+
+  // TODO (43081j): This is skipped until #720 is fixed
+  it.skip('should hide when clicked outside container and initially open', async () => {
+    const el = await fixture<SlDropdown>(html`
+      <sl-dropdown open>
+        <sl-button slot="trigger" caret>Toggle</sl-button>
+        <sl-menu>
+          <sl-menu-item>Item 1</sl-menu-item>
+        </sl-menu>
+      </sl-dropdown>
+    `);
+
+    document.body.dispatchEvent(
+      new MouseEvent('mousedown', {
+        bubbles: true
+      })
+    );
+
+    await el.updateComplete;
+
+    expect(el.open).to.be.false;
+  });
+
+  it('should hide when clicked outside container', async () => {
+    const el = await fixture<SlDropdown>(html`
+      <sl-dropdown>
+        <sl-button slot="trigger" caret>Toggle</sl-button>
+        <sl-menu>
+          <sl-menu-item>Item 1</sl-menu-item>
+        </sl-menu>
+      </sl-dropdown>
+    `);
+    const trigger = el.shadowRoot!.querySelector<HTMLElement>('[part="trigger"]')!;
+
+    trigger.click();
+
+    await el.updateComplete;
+
+    document.body.dispatchEvent(
+      new MouseEvent('mousedown', {
+        bubbles: true
+      })
+    );
+
+    await el.updateComplete;
+
+    expect(el.open).to.be.false;
+  });
 });

src/components/dropdown/dropdown.ts

@@ -209,11 +209,6 @@ export default class SlDropdown extends LitElement {
   }
 
   handleTriggerKeyDown(event: KeyboardEvent) {
-    const menu = this.getMenu()!;
-    const menuItems = menu.defaultSlot.assignedElements({ flatten: true }) as SlMenuItem[];
-    const firstMenuItem = menuItems[0];
-    const lastMenuItem = menuItems[menuItems.length - 1];
-
     // Close when escape or tab is pressed
     if (event.key === 'Escape') {
       this.focusOnTrigger();
@@ -229,35 +224,45 @@ export default class SlDropdown extends LitElement {
       return;
     }
 
-    // When up/down is pressed, we make the assumption that the user is familiar with the menu and plans to make a
-    // selection. Rather than toggle the panel, we focus on the menu (if one exists) and activate the first item for
-    // faster navigation.
-    if (['ArrowDown', 'ArrowUp', 'Home', 'End'].includes(event.key)) {
-      event.preventDefault();
+    const menu = this.getMenu();
 
-      // Show the menu if it's not already open
-      if (!this.open) {
-        this.show();
+    if (menu) {
+      const menuItems = menu.defaultSlot.assignedElements({ flatten: true }) as SlMenuItem[];
+      const firstMenuItem = menuItems[0];
+      const lastMenuItem = menuItems[menuItems.length - 1];
+
+      // When up/down is pressed, we make the assumption that the user is familiar with the menu and plans to make a
+      // selection. Rather than toggle the panel, we focus on the menu (if one exists) and activate the first item for
+      // faster navigation.
+      if (['ArrowDown', 'ArrowUp', 'Home', 'End'].includes(event.key)) {
+        event.preventDefault();
+
+        // Show the menu if it's not already open
+        if (!this.open) {
+          this.show();
+        }
+
+        if (menuItems.length > 0) {
+          // Focus on the first/last menu item after showing
+          requestAnimationFrame(() => {
+            if (event.key === 'ArrowDown' || event.key === 'Home') {
+              menu.setCurrentItem(firstMenuItem);
+              firstMenuItem.focus();
+            }
+
+            if (event.key === 'ArrowUp' || event.key === 'End') {
+              menu.setCurrentItem(lastMenuItem);
+              lastMenuItem.focus();
+            }
+          });
+        }
       }
 
-      // Focus on the first/last menu item after showing
-      requestAnimationFrame(() => {
-        if (event.key === 'ArrowDown' || event.key === 'Home') {
-          menu.setCurrentItem(firstMenuItem);
-          firstMenuItem.focus();
-        }
-
-        if (event.key === 'ArrowUp' || event.key === 'End') {
-          menu.setCurrentItem(lastMenuItem);
-          lastMenuItem.focus();
-        }
-      });
-    }
-
-    // Other keys bring focus to the menu and initiate type-to-select behavior
-    const ignoredKeys = ['Tab', 'Shift', 'Meta', 'Ctrl', 'Alt'];
-    if (this.open && !ignoredKeys.includes(event.key)) {
-      menu.typeToSelect(event);
+      // Other keys bring focus to the menu and initiate type-to-select behavior
+      const ignoredKeys = ['Tab', 'Shift', 'Meta', 'Ctrl', 'Alt'];
+      if (this.open && !ignoredKeys.includes(event.key)) {
+        menu.typeToSelect(event);
+      }
     }
   }