fix(expressive-modal): ensure waiting for transitionend event

packages/web-components/src/components/expressive-modal/expressive-modal.ts

@@ -1,7 +1,7 @@
 /**
  * @license
  *
- * Copyright IBM Corp. 2020
+ * Copyright IBM Corp. 2020, 2021
  *
  * This source code is licensed under the Apache-2.0 license found in the
  * LICENSE file in the root directory of this source tree.
@@ -20,6 +20,7 @@ import {
 } from 'lit-element';
 import ddsSettings from '@carbon/ibmdotcom-utilities/es/utilities/settings/settings.js';
 import settings from 'carbon-components/es/globals/js/settings.js';
+import on from 'carbon-components/es/globals/js/misc/on';
 import { selectorTabbable } from 'carbon-web-components/es/globals/settings.js';
 import HostListener from 'carbon-web-components/es/globals/decorators/host-listener.js';
 import HostListenerMixin from 'carbon-web-components/es/globals/mixins/host-listener.js';
@@ -224,6 +225,29 @@ class DDSExpressiveModal extends StableSelectorMixin(HostListenerMixin(LitElemen
     }
   }
 
+  /**
+   * @param timeout The number of milliseconds as the longest time waiting for `transitionend` event.
+   * @returns A promise that is resolves when `transitionend` on the host element fires.
+   */
+  private _waitForTransitionEnd(timeout: number = 1000) {
+    return new Promise(resolve => {
+      let done = false;
+      let hTransitionEnd;
+      const handleResolve = () => {
+        if (hTransitionEnd) {
+          hTransitionEnd.release();
+          hTransitionEnd = null;
+        }
+        if (!done) {
+          resolve(undefined);
+          done = true;
+        }
+      };
+      on(this, 'transitionend', handleResolve);
+      setTimeout(handleResolve, timeout);
+    });
+  }
+
   /**
    * @returns The header content.
    */
@@ -320,7 +344,7 @@ class DDSExpressiveModal extends StableSelectorMixin(HostListenerMixin(LitElemen
       if (this.open) {
         this._launcher = this.ownerDocument!.activeElement;
         const primaryFocusNode = this.querySelector((this.constructor as typeof DDSExpressiveModal).selectorPrimaryFocus);
-        await (this.constructor as typeof DDSExpressiveModal)._delay();
+        await this._waitForTransitionEnd();
         if (primaryFocusNode) {
           // For cases where a `carbon-web-components` component (e.g. `<bx-btn>`) being `primaryFocusNode`,
           // where its first update/render cycle that makes it focusable happens after `<bx-modal>`'s first update/render cycle

packages/web-components/src/components/locale-modal/locale-modal.ts

@@ -1,7 +1,7 @@
 /**
  * @license
  *
- * Copyright IBM Corp. 2020
+ * Copyright IBM Corp. 2020, 2021
  *
  * This source code is licensed under the Apache-2.0 license found in the
  * LICENSE file in the root directory of this source tree.
@@ -187,6 +187,16 @@ class DDSLocaleModal extends DDSExpressiveModal {
     return `${ddsPrefix}-locale-search`;
   }
 
+  /**
+   * A selector selecting the nodes that should be focused when modal gets open.
+   */
+  static get selectorPrimaryFocus() {
+    return `
+      [data-modal-primary-focus],
+      ${ddsPrefix}-region-item
+    `;
+  }
+
   static get stableSelector() {
     return `${ddsPrefix}--locale-modal`;
   }