fix: avoid emitting input event if initial value is null

fixes #21

Author: RonaldJerez

src/core.js

@@ -135,8 +135,11 @@ export function updateCursor(event, originalValue, originalPosition) {
  * @param {Event} [event] The event that triggered this this update, null if not triggered by an input event
  */
 export function updateValue(el, vnode, { emit = true, force = false } = {}, event) {
-  const { config, oldValue } = el[CONFIG_KEY]
-  const currentValue = vnode && vnode.data.model ? vnode.data.model.value : el.value
+  let { config, oldValue } = el[CONFIG_KEY]
+  let currentValue = vnode && vnode.data.model ? vnode.data.model.value : el.value
+
+  oldValue = oldValue || ''
+  currentValue = currentValue || ''
 
   if (force || oldValue !== currentValue) {
     let newValue = masker(currentValue, config)
@@ -161,7 +164,7 @@ export function updateValue(el, vnode, { emit = true, force = false } = {}, even
     }
 
     // this part needs to be outside the above IF statement for vuetify in firefox
-    // draweback is that we endup with two's input events in firefox
+    // drawback is that we endup with two's input events in firefox
     emit && el.dispatchEvent(FacadeInputEvent())
   }
 }

src/directive.js

@@ -6,12 +6,11 @@ export default {
     el = core.getInputElement(el)
     el.addEventListener('input', core.inputHandler, true)
 
-    el[CONFIG_KEY] = {
-      config: core.normalizeConfig(value, modifiers)
-    }
+    const config = core.normalizeConfig(value, modifiers)
+    el[CONFIG_KEY] = { config }
 
     // set initial value
-    core.updateValue(el, vnode)
+    core.updateValue(el, vnode, { force: config.prefill })
   },
 
   update: (el, { value, oldValue, modifiers }, vnode) => {

tests/component.test.js

@@ -16,6 +16,14 @@ describe('Component', () => {
     expect(wrapper.vm.maskedValue).toBe('123-4')
   })
 
+  test('Should not emit input if initial value is null', () => {
+    const value = null
+    const mask = '####'
+
+    const wrapper = createWrapper({ value, mask })
+    expect(wrapper.emitted().input).toBeFalsy()
+  })
+
   test('Updating the value should update the values', async () => {
     const value = '1234'
     const mask = '###-#'
@@ -69,8 +77,7 @@ describe('Component', () => {
     const input = wrapper.find('input')
 
     input.trigger('change')
-    // only the initial input should be present
-    expect(wrapper.emitted().input.length).toEqual(1)
+    expect(wrapper.emitted().input).toBeFalsy()
   })
 
   test('Adding a format function should call that function on input', async () => {