label error line

[missyii]

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Vue.js version and component version

Reproduction Link

• A minimal JSBin, JSFiddle, Codepen, or a GitHub repository that can reproduce the bug.
• You could start with this template: https://jsfiddle.net/39epgLj0/

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What is Expected?

What is actually happening?

[missyii]

how can i label error line, just like add a error-icon in front of the error line, or add other style?

[surmon-china]

@missyii https://codemirror.net/demo/widget.html https://github.com/surmon-china/vue-codemirror/issues/67#issuecomment-419130484