Fix bug when pushing to an empty array (longhand) (#168)

* Fix bug when pushing to an empty array (longhand)

* Adding a changeset

.changeset/small-shrimps-walk.md

@@ -0,0 +1,5 @@
+---
+"corset": patch
+---
+
+Update when pushing to an empty array using longhand each

src/multi-binding.js

@@ -280,7 +280,7 @@ export class MultiBinding extends Binding {
 
     // Fill in the defaults by looking at the valueMap for holes.
     for(let [key, values] of valueMap) {
-      if(!dirtyKeys.has(key)) continue;
+      let isDirty = dirtyKeys.has(key);
       // valueMap is always appended from a longhand prop.
       let numOfValues = this.numberOfValues;
       let keyed = this.defn.feat & features.keyed;
@@ -298,7 +298,7 @@ export class MultiBinding extends Binding {
           values.push(...current);
         }
       }
-      yield [/** @type {[K, ...any[]]} */(/** @type {unknown} */(values)), true];
+      yield [/** @type {[K, ...any[]]} */(/** @type {unknown} */(values)), isDirty];
     }
 
     // Yield out to reset to initial state.

test/test-each.js

@@ -140,4 +140,29 @@ QUnit.test('Changes to items result in updates', assert => {
   bind().update(root);
   assert.equal(ul.firstElementChild.textContent, 'one');
   assert.equal(ul.firstElementChild.nextElementSibling.textContent, 'two !!');
+});
+
+QUnit.test('Pushing to an empty list (longhand)', assert => {
+  let root = document.createElement('main');
+  root.innerHTML = `<ul></ul><template><li></li></template>`;
+  let items = [];
+  function bind() {
+    return sheet`
+      ul {
+        each-items: ${items};
+        each-template: select(template);
+      }
+
+      li {
+        text: get(item(), label);
+      }
+    `;
+  }
+  let ul = root.firstElementChild;
+  bind().update(root);
+
+  items.push({ label: 'works' });
+  bind().update(root);
+  assert.equal(ul.children.length, 1);
+  assert.equal(ul.firstElementChild.textContent, 'works');
 });