Drop support for vue files to avoid conflicts with eslint-plugin-vue

[BPScott]

eslint-plugin-html and eslint-plugin-vue conflict with each other as per https://github.com/vuejs/eslint-plugin-vue/blob/562fde184a7a37f551fc98711a0bb4233c749606/README.md#why-doesnt-it-work-on-vue-file

This is because the processor in eslint-plugin-vue does not modify the vue file when processing the file, while eslint-plugin-vue's processor extracts just the <script> element.

This then has a knock-on effect in eslint-plugin-prettier because it doesn't know what parser it should use (if someone is using eslint-plugin-vue then it is acting upon a full vue file so it should use the vue parser, if someone is using eslint-plugin-html it is acting upon a JS fragment so it should use the babylon parser).

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I feel the easiest approach for interoperability is to remove support for .vue files and to direct people to use eslint-plugin-vue if they want to lint their vue files. This has the side effect of offering fuller linting for the vue file as it supports linting the <template> and <style> tags in addition to the <script> tag

[BenoitZugmeyer]

This is a known issue, and both plugin document it in its README (see). The only thing I can do to go further is to remove the .vue from the default extensions.

[BPScott]

Thanks for that context, I missed that section in your readme.

The only thing I can do to go further is to remove the .vue from the default extensions.

I think that would be best. Doing so in v5 as a breaking change makes most sense to me and it sounds like you're already planning a v5 release anyway. As it currently stands it is not possible for somebody to use eslint-plugin-vue >=3.0.0 and eslint-plugin-html at the same time without losing the linting of the <template> and <style> sections.

Removing .vue from the default extensions would allow you to update the README to say something like:

eslint-plugin-vue v3.0.0 and later versions are incompatible with eslint-plugin-html versions earlier than v5.0.0. To ensure eslint-plugin-vue functionality is not affected you must use eslint-plugin-html v5.0.0 or later.