vue/no-arrow-functions-in-watch 
disallow using arrow functions to define watcher
- ⚙️ This rule is included in all of 
"plugin:vue/vue3-essential",*.configs["flat/essential"],"plugin:vue/essential",*.configs["flat/vue2-essential"],"plugin:vue/vue3-strongly-recommended",*.configs["flat/strongly-recommended"],"plugin:vue/strongly-recommended",*.configs["flat/vue2-strongly-recommended"],"plugin:vue/vue3-recommended",*.configs["flat/recommended"],"plugin:vue/recommended"and*.configs["flat/vue2-recommended"]. 
📖 Rule Details 
This rule disallows using arrow functions when defining a watcher. Arrow functions bind to their parent context, which means they will not have access to the Vue component instance via this. See here for more details.
🔧 Options 
Nothing.
🚀 Version 
This rule was introduced in eslint-plugin-vue v7.0.0