fix(picker): manage focus to prevent a11y issues.

Author: joselrio

core/src/components/picker/picker.tsx

@@ -135,12 +135,63 @@ export class Picker implements ComponentInterface {
    * function that has been set in onPointerDown
    * so that we enter/exit input mode correctly.
    */
-  private onClick = () => {
+  private onClick = (ev: PointerEvent) => {
     const { actionOnClick } = this;
     if (actionOnClick) {
       actionOnClick();
       this.actionOnClick = undefined;
     }
+
+    /**
+     * In order to avoid a11y issues we must manage focus
+     * on the picker columns and picker itself.
+     * This is because once picker is clicked we got an issue/warning because
+     * picker input is being focused, and once it has tabindex -1 it can't be focused,
+     * which ends on focusing the picker itself.
+     * During the process above we fall into issues since there is an element
+     * with tabindex -1 and aria-hidden='true' that is focused, which is not allowed.
+     * That said and since onClick is being propagated to the picker itself, we need to
+     * manage focus on the picker columns and picker itself to avoid the issue.
+     */
+    const clickedTarget = ev.target as HTMLElement;
+    let elementToFocus: HTMLElement | null = null;
+
+    switch (clickedTarget.tagName) {
+      case 'ION-PICKER':
+        /**
+         * If the user clicked the picker itself
+         * then we should focus the first picker options
+         * so that users can scroll through them.
+         */
+        const ionPickerColumn = this.el.querySelector('ion-picker-column');
+        elementToFocus = ionPickerColumn?.shadowRoot?.querySelector('.picker-opts') as HTMLElement | null;
+        break;
+
+      case 'ION-PICKER-COLUMN':
+        /**
+         * If the user clicked a picker column
+         * then we should focus its own picker options
+         * so that users can scroll through them.
+         */
+        elementToFocus = clickedTarget.shadowRoot?.querySelector('.picker-opts') as HTMLElement | null;
+        break;
+
+      case 'ION-PICKER-COLUMN-OPTION':
+        /**
+         * If the user clicked a picker column option
+         * then we should focus its picker options parent so that
+         * users can scroll through them.
+         */
+        const ionPickerColumnOption = clickedTarget.closest('ion-picker-column');
+        if (ionPickerColumnOption) {
+          elementToFocus = ionPickerColumnOption.shadowRoot?.querySelector('.picker-opts') as HTMLElement | null;
+        }
+        break;
+    }
+
+    if (elementToFocus) {
+      elementToFocus.focus();
+    }
   };
 
   /**
@@ -537,7 +588,10 @@ export class Picker implements ComponentInterface {
 
   render() {
     return (
-      <Host onPointerDown={(ev: PointerEvent) => this.onPointerDown(ev)} onClick={() => this.onClick()}>
+      <Host
+        onPointerDown={(ev: PointerEvent) => this.onPointerDown(ev)}
+        onClick={(ev: PointerEvent) => this.onClick(ev)}
+      >
         <input
           aria-hidden="true"
           tabindex={-1}