:bug: Allows model.fill to work with checkbox arrays (#3676)

packages/alpinejs/src/directives/x-model.js

@@ -70,8 +70,10 @@ directive('model', (el, { modifiers, expression }, { effect, cleanup }) => {
         setValue(getInputValue(el, modifiers, e, getValue()))
     })
     
-    if (modifiers.includes('fill') && [null, ''].includes(getValue())) {
-        el.dispatchEvent(new Event(event, {}));
+    if (modifiers.includes('fill'))
+        if ([null, ''].includes(getValue())
+            || (el.type === 'checkbox' && Array.isArray(getValue()))) {
+            el.dispatchEvent(new Event(event, {}));
     }
     // Register the listener removal callback on the element, so that
     // in addition to the cleanup function, x-modelable may call it.

tests/cypress/integration/directives/x-model.spec.js

@@ -186,5 +186,16 @@ test('x-model with fill modifier respects number modifier',
     }
 );
 
-
+test(
+    'x-model with fill applies on checkboxes bound to array',
+    html`
+        <div x-data="{ a: ['456'] }">
+            <input type="checkbox" x-model.fill="a" value="123" checked />
+            <input type="checkbox" x-model.fill="a" value="456" />
+        </div>
+    `,
+    ({ get }) => {
+        get('[x-data]').should(haveData('a', ['123']));
+    }
+);