Add deepData option to vue/no-unused-properties rule (#1387)

* Add deepData option to `vue/no-unused-properties`

* update

* update

* update

Author: ota-meshi

docs/rules/no-unused-properties.md

@@ -54,7 +54,8 @@ This rule cannot be checked for use in other components (e.g. `mixins`, Property
 ```json
 {
   "vue/no-unused-properties": ["error", {
-    "groups": ["props"]
+    "groups": ["props"],
+    "deepData": false
   }]
 }
 ```
@@ -65,6 +66,7 @@ This rule cannot be checked for use in other components (e.g. `mixins`, Property
   - `"computed"`
   - `"methods"`
   - `"setup"`
+- `"deepData"` (`boolean`) If `true`, the object of the property defined in `data` will be searched deeply. Default is `false`. Include `"data"` in `groups` to use this option.
 
 ### `"groups": ["props", "data"]`
 
@@ -108,6 +110,32 @@ This rule cannot be checked for use in other components (e.g. `mixins`, Property
 
 </eslint-code-block>
 
+### `{ "groups": ["props", "data"], "deepData": true }`
+
+<eslint-code-block :rules="{'vue/no-unused-properties': ['error', {groups: ['props', 'data'], deepData: true}]}">
+
+```vue
+<template>
+  <Foo :param="state.used">
+</template>
+<script>
+  export default {
+    data() {
+      return {
+        state: {
+          /* ✓ GOOD */
+          used: null,
+          /* ✗ BAD (`state.unused` data not used) */
+          unused: null
+        }
+      }
+    }
+  }
+</script>
+```
+
+</eslint-code-block>
+
 ### `"groups": ["props", "computed"]`
 
 <eslint-code-block :rules="{'vue/no-unused-properties': ['error', {groups: ['props', 'computed']}]}">