fix(VDatePicker): display proper year when model is null (#5672)

fixes #5663

Author: jacekkarczmarczyk

packages/vuetify/src/components/VDatePicker/VDatePicker.js

@@ -297,7 +297,7 @@ export default {
         props: {
           date: this.value ? this.formatters.titleDate(this.value) : '',
           selectingYear: this.activePicker === 'YEAR',
-          year: this.formatters.year(`${this.inputYear}`),
+          year: this.formatters.year(this.value ? `${this.inputYear}` : this.tableDate),
           yearIcon: this.yearIcon,
           value: this.multiple ? this.value[0] : this.value
         },

packages/vuetify/test/unit/components/VDatePicker/VDatePicker.date.spec.js

@@ -17,6 +17,19 @@ test('VDatePicker.js', ({ mount, compileToFunctions }) => {
     expect(header.text()).toBe('November 2005')
   })
 
+  it('should display the correct year when model is null', () => {
+    const wrapper = mount(VDatePicker, {
+      propsData: {
+        value: null,
+        pickerDate: '2013-01'
+      }
+    })
+
+    const year = wrapper.find('.v-date-picker-title__year')[0]
+
+    expect(year.text()).toBe('2013')
+  })
+
   it('should match snapshot with default settings', () => {
     const wrapper = mount(VDatePicker, {
       propsData: {