fix(VCombobox): correctly handle duplicate items (#13366)

fixes #12351

* fix(VCombobox): correctly handle duplicate items

* fix(VCombobox): copy object beore it is removed

* fix(VCombobox): copy object before it is removed

* chore: resolve merge conflicts

* chore: add deleted changes

packages/vuetify/src/components/VCombobox/VCombobox.ts

@@ -223,7 +223,15 @@ export default VAutocomplete.extend({
         return this.updateEditing()
       }
 
-      const index = this.selectedItems.indexOf(this.internalSearch)
+      const index = this.selectedItems.findIndex(item =>
+        this.internalSearch === this.getText(item))
+
+      // If the duplicate item is an object,
+      // copy it, so that it can be added again later
+      const itemToSelect = index > -1 && typeof this.selectedItems[index] === 'object'
+        ? Object.assign({}, this.selectedItems[index])
+        : this.internalSearch
+
       // If it already exists, do nothing
       // this might need to change to bring
       // the duplicated item to the last entered
@@ -239,7 +247,8 @@ export default VAutocomplete.extend({
       // TODO: find out where
       if (menuIndex > -1) return (this.internalSearch = null)
 
-      this.selectItem(this.internalSearch)
+      this.selectItem(itemToSelect)
+
       this.internalSearch = null
     },
     onPaste (event: ClipboardEvent) {

packages/vuetify/src/components/VCombobox/__tests__/VCombobox-multiple.spec.ts

@@ -520,4 +520,32 @@ describe('VCombobox.ts', () => {
 
     expect(change).toHaveBeenLastCalledWith(['foo'])
   })
+
+  // https://github.com/vuetifyjs/vuetify/issues/12351
+  it('should correctly handle duplicate items', async () => {
+    const { wrapper, change } = createMultipleCombobox({
+      chips: true,
+      multiple: true,
+      items: [
+        { text: 'foo', value: 'foo' },
+        { text: 'bar', value: 'bar' },
+      ],
+      value: [
+        { text: 'foo', value: 'foo' },
+      ],
+    })
+
+    const input = wrapper.find('input')
+    const element = input.element as HTMLInputElement
+
+    input.trigger('focus')
+    element.value = 'foo'
+    input.trigger('input')
+    await wrapper.vm.$nextTick()
+
+    input.trigger('keydown.tab')
+    await wrapper.vm.$nextTick()
+
+    expect(change).toHaveBeenLastCalledWith([{ text: 'foo', value: 'foo' }])
+  })
 })