计算属性中的意外副作用

我不确定为什么在下面的代码中计算机属性错误会导致意外的副作用。

错误：

 ✘  https://google.com/#q=vue%2Fno-side-effects-in-computed-properties  Unexpected side effect in "orderMyReposByStars" computed property            
  src/components/HelloWorld.vue:84:14
        return this.myRepos.sort((a, b) => a.stargazers_count < b.stargazers_count)

的HTML：

<div v-if="myRepos && myRepos.length > 0">
  <h3>My Repos</h3>
  <ul>
    <li v-for="repo in orderMyReposByStars" v-bind:key="repo.id">
      <div class="repo">
        {{repo.name}}
        <div class="pull-right">
          <i class="fas fa-star"></i>
          <span class="bold">{{repo.stargazers_count}}</span>
        </div>
      </div>
    </li>
  </ul>
</div>

js：

export default {
  name: 'HelloWorld',
  data () {
    return {
      myRepos: null,  <-- THIS IS ULTIMATELY AN ARRAY OF OBJECTS
    }
  },
  computed: {
    orderMyReposByStars: function () {
      return this.myRepos.sort((a, b) => a.stargazers_count < b.stargazers_count)
    },
...

据我所知，根据此处的文档，这看起来是正确的https://vuejs.org/v2/guide/list.html#Displaying-Filtered-Sorted-Results