There is es6 related code in the template, and the polyfill is not automatically introduced after compilation

[zhouxinyong]

Version

15.9.6

Reproduction link

https://github.com/zhouxinyong/vue2-build-issue

Steps to reproduce

1. yarn
2. add v-if="list.inclues(4)" in template at file: App.vue
3. yarn build
4. check the build file chunk-vendors.js

What is expected?

auto import polyfill with Array.prototype.includes

What is actually happening?

no polyfill with Array.prototype.includes

---

when i change v-if="list.inclues(4)" to v-if="checkKey(4)", and add a method like below

methods: {
  checkKey (key) {
    return this.list.includes(key)
  }
}

then run yarn build, check the build file chunk-vendors.js, there has auto import polyfill with Array.prototype.includes

[haoqunjiang]

Same reason as vuejs/vue#11088 (comment)
It's because, in vue-loader v15, the template compiler isn't chained with other loaders for js.
This is solved in v16, but v16 can only compile Vue 3 code.

To backport this feature to v15 requires much dedicated time and energy, so it's beyond our capacity for now. So, I'm afraid it's a "won't fix".