fix(aria/combobox): calc highlight state on open

Author: wagnermaciel

src/aria/combobox/combobox.spec.ts

@@ -499,6 +499,31 @@ describe('Combobox', () => {
         input('');
         expect(getOptions().length).toBe(50);
       });
+
+      it('should determine the highlighted state on open', () => {
+        setupCombobox({filterMode: 'highlight'});
+        focus();
+        input('N');
+        expect(inputElement.value).toBe('Nebraska');
+        expect(inputElement.selectionEnd).toBe(8);
+        expect(inputElement.selectionStart).toBe(1);
+        expect(getOptions().length).toBe(8);
+
+        escape(); // close
+        inputElement.selectionStart = 2; // Change highlighting
+        down(); // open
+
+        expect(inputElement.value).toBe('Nebraska');
+        expect(inputElement.selectionEnd).toBe(8);
+        expect(inputElement.selectionStart).toBe(2);
+        expect(getOptions().length).toBe(6);
+
+        escape(); // close
+        inputElement.selectionStart = 3; // Change highlighting
+        down(); // open
+
+        expect(getOptions().length).toBe(1);
+      });
     });
 
     // describe('with programmatic value changes', () => {

src/aria/ui-patterns/combobox/combobox.ts

@@ -391,6 +391,17 @@ export class ComboboxPattern<T extends ListItem<V>, V> {
   open(nav?: {first?: boolean; last?: boolean}) {
     this.expanded.set(true);
 
+    const inputEl = this.inputs.inputEl();
+
+    if (inputEl) {
+      const isHighlighting = inputEl.selectionStart !== inputEl.value.length;
+      this.inputs.inputValue?.set(inputEl.value.slice(0, inputEl.selectionStart || 0));
+
+      if (!isHighlighting) {
+        this.highlightedItem.set(undefined);
+      }
+    }
+
     if (nav?.first) {
       this.first();
     }