[vue/valid-template-root] Incorrect detection of root element when using v-if/v-else directives

[ThibaultVlacich]

Tell us about your environment

• ESLint version: 6.6.0
• eslint-plugin-vue version: 6.0.0
• Node version: 13.0.1

Please show your full configuration:

module.exports = {
  root: true,
  env: {
    browser: true,
    node: true
  },
  parserOptions: {
    parser: 'babel-eslint'
  },
  extends: [
    '@nuxtjs',
    'prettier',
    'prettier/vue',
    'plugin:prettier/recommended',
    'plugin:nuxt/recommended'
  ],
  plugins: [
    'prettier'
  ],
  // add your custom rules here
  rules: {
    'vue/no-v-html': 'off'
  }
}

What did you do?

<template>
  <div
    v-if="status === 'LOADING'"
    class="d-flex justify-content-center loading"
  >
    Loading comments
    <span class="one">.</span>
    <span class="two">.</span>
    <span class="three">.</span>
  </div>

  <div v-else-if="status === 'LOADED'">
    <h4 class="comments-head">
      <font-awesome-icon :icon="['far', 'comments']" class="mx-2" />
      {{ `${commentsCount} comment${commentsCount > 1 ? 's' : ''}` }}
    </h4>

    <div v-for="comment in comments" :key="comment.id" class="comment">
      <div class="meta">
        <span class="author">{{ comment.author.username }}</span>
        on
        <time :datetime="comment.publishedAt" class="date">
          {{ comment.publishedAt | formatDate }}
        </time>
      </div>

      <div v-html="comment.content" class="content"></div>
    </div>
    <div v-if="comments.length === 0" class="no-comments text-center py-3">
      There are no comments.
    </div>

    <b-pagination
      v-if="comments.length > 0"
      v-model="page"
      :total-rows="commentsCount"
      :per-page="perPage"
      size="sm"
      align="center"
    ></b-pagination>

    <div v-if="$auth.loggedIn" class="add-comment">
      <b-form
        v-if="['WAITING', 'SENDING'].includes(newCommentStatus)"
        @submit.prevent.stop="addComment"
      >
        <h4 class="comments-head">
          Add a comment
        </h4>

        <classic-editor
          id="new-comment-body"
          v-model="newCommentContent"
          :config="{ toolbar: ['bold', 'italic'], readOnly: true }"
          :disabled="newCommentStatus === 'SENDING'"
        ></classic-editor>

        <div class="mt-3 d-flex justify-content-end">
          <b-button
            :disabled="
              newCommentStatus === 'SENDING' || newCommentContent.length === 0
            "
            variant="primary"
            type="submit"
          >
            <font-awesome-icon
              v-if="newCommentStatus === 'SENDING'"
              icon="spinner"
              spin
              class="mr-2"
            />
            Send
          </b-button>
        </div>
      </b-form>

      <b-alert :show="newCommentStatus === 'SENT'" variant="success">
        Your comment has been successfully added.
      </b-alert>
      <b-alert :show="newCommentStatus === 'ERROR'" variant="danger">
        {{ newCommentErrorMessage }}
      </b-alert>
    </div>
  </div>
</template>

What did you expect to happen?

This code does not trigger an error

What actually happened?

The vue/valid-template-root rule throws an error. This exact same code was working on ESLint 5 / eslint-plugin-nuxt 5.2.3, and I'm seeing nothing in the changelog that could explain why it's not working anymore.

components\poll\Comments.vue
12:3 error The template root requires exactly one element vue/valid-template-root

[ota-meshi]

Thank you for this issue.

I checked your issue in the DEMO but could not reproduce it.
Also, I tried it on my local PC [email protected] but could not reproduce it.

Can you tell me the version of eslint-plugin-vue you are using?

eslint-plugin-vue version: 6.6.0

The latest version of current eslint-plugin-vue is 6.0.0.

[ThibaultVlacich]

My bad, typo. I am indeed using [email protected], not 6.6.0.
Your demo link seems to be using [email protected], which does not raise any error as expected.

The issue is present only on the 6.0.0 version. I have the issue both on my local PC, and my CI integration.

[ota-meshi]

Thank you for telling me which version you are using.

The eslint-plugin-nuxt version may be affected.
If you use eslint-plugin-nuxt version 0.4.3 or earlier with [email protected], the vue-eslint-parser version not match, which may cause issues.
What version of eslint-plugin-nuxt are you using?

[ThibaultVlacich]

[email protected], but I think @nuxtjs/eslint-config has not been updated yet.
I'll wait for this package to be updated and see if issue it still present.

[ota-meshi]

If you have a problem with the version of vue-eslint-parser, you may be able to solve the problem by:

• Install vue-eslint-parser explicitly.

npm install -D vue-eslint-parser@^6.0.5

• Specify vue-eslint-parser clearly in eslintrc.js.

+  parser: require.resolve('vue-eslint-parser'),

Can you try this?

[Miaoxingren]

Same problem here. Please look at this repo: https://github.com/Miaoxingren/test-nuxt-eslint. Downgrade eslint-plugin-nuxt to @0.4.3 solved the problem.

[ota-meshi]

Hi @Miaoxingren
I checked package-lock.json which reproduced the phenomenon. There seems to be a problem with the dependency of @nuxtjs/eslint-config.
It seems that the version of eslint-plugin-vue and vue-eslint-parser is in conflicts because of the dependency of @nuxtjs/eslint-config.

[ThibaultVlacich]

If you have a problem with the version of vue-eslint-parser, you may be able to solve the problem by:

* Install `vue-eslint-parser` explicitly.

npm install -D vue-eslint-parser@^6.0.5

* Specify `vue-eslint-parser` clearly in eslintrc.js.

+  parser: require.resolve('vue-eslint-parser'),

Can you try this?

No success.

[ota-meshi]

@ThibaultVlacich
I still don't know the cause of this issue.
If you can, please tell me your repository where this issue can be reproduced.

[ThibaultVlacich]

I made a simple repro project that showcase the issue: https://github.com/ThibaultVlacich/valid-template-root-eslint-6

The master branch is update to ESLint 6, and the issue is present. There is also an eslint-5 branch, to show that it was working without any problem before.

[ota-meshi]

Thank you for telling me your repository.

I checked the node_modules in your repository.
In node_modules, [email protected] and [email protected] were actually used.

[email protected] and [email protected] are not compatible.
I think you can avoid this problem by installing [email protected].

[ThibaultVlacich]

I've been able to temporarily fix my issue by adding this to my package.json (using Yarn), until https://github.com/nuxt/eslint-config is updated :

"resolutions": {
  "@nuxtjs/eslint-config/eslint-plugin-vue": "^6.0.1"
}

[ota-meshi]

I close this isssue because I found that the dependency of @nuxtjs/eslint-config was the cause.
Keep track of the nuxt/eslint#69.