refactor: add empty v-bind warning(re vuejs#7973) (vuejs#7988)

* refactor: add empty v-bind warnings

re vuejs#7973

* Update index.js

src/compiler/parser/index.js

@@ -528,6 +528,14 @@ function processAttrs (el) {
  name = name.replace(bindRE, '')
  value = parseFilters(value)
  isProp = false
+ if (
+ process.env.NODE_ENV !== 'production' &&
+ value.trim().length === 0
+ ) {
+ warn(
+ `The value for a v-bind expression cannot be empty. Found in "v-bind:${name}"`
+ )
+ }
  if (modifiers) {
  if (modifiers.prop) {
  isProp = true

test/unit/modules/compiler/parser.spec.js

@@ -510,6 +510,11 @@ describe('parser', () => {
  expect(ast.props[0].value).toBe('msg')
  })
 
+ it('empty v-bind expression', () => {
+ parse('<div :empty-msg=""></div>', baseOptions)
+ expect('The value for a v-bind expression cannot be empty. Found in "empty-msg"').toHaveBeenWarned()
+ })
+
  // #6887
  it('special case static attribute that must be props', () => {
  const ast = parse('<video muted></video>', baseOptions)