[New] no-unused-state: Support ignore option

Author: fwgood

docs/rules/no-unused-state.md

@@ -45,3 +45,16 @@ var UnusedGetInitialStateTest = createReactClass({
   }
 })
 ```
+
+## Rule Options
+
+This rule can take one argument to ignore some specific states during validation.
+
+```js
+...
+"react/no-unused-state": [<enabled>, { ignore: <ignore> }]
+...
+```
+
+- `enabled`: for enabling the rule. 0=off, 1=warn, 2=error. Defaults to 0.
+- `ignore`: optional array of states name to ignore during validation.

lib/rules/no-unused-state.js

@@ -90,10 +90,34 @@ module.exports = {
 
     messages,
 
-    schema: [],
+    schema: [{
+      type: 'object',
+      properties: {
+        ignore: {
+          type: 'array',
+          items: {
+            type: 'string',
+          },
+          uniqueItems: true,
+        },
+      },
+      additionalProperties: false,
+    }],
   },
 
   create(context) {
+    const defaults = { skipShapeProps: true, customValidators: [], ignore: [] };
+    const configuration = Object.assign({}, defaults, context.options[0] || {});
+
+    /**
+     * Checks if the state is ignored
+     * @param {string} name Name of the state to check.
+     * @returns {boolean} True if the state is ignored, false if not.
+     */
+    function isIgnored(name) {
+      return configuration.ignore.indexOf(name) !== -1;
+    }
+
     // Non-null when we are inside a React component ClassDeclaration and we have
     // not yet encountered any use of this.state which we have chosen not to
     // analyze. If we encounter any such usage (like this.state being spread as
@@ -223,7 +247,7 @@ module.exports = {
       // Report all unused state fields.
       classInfo.stateFields.forEach((node) => {
         const name = getName(node.key);
-        if (!classInfo.usedStateFields.has(name)) {
+        if (!classInfo.usedStateFields.has(name) && !isIgnored(name)) {
           report(context, messages.unusedStateField, 'unusedStateField', {
             node,
             data: {

tests/lib/rules/no-unused-state.js

@@ -1110,6 +1110,58 @@ eslintTester.run('no-unused-state', rule, {
         }
       `,
       features: ['types', 'class fields'],
+    },
+    {
+      code: `
+        var UnusedGetInitialStateTest = createReactClass({
+          getInitialState: function() {
+            return { foo: 0 };
+          },
+          render: function() {
+            return <SomeComponent />;
+          }
+        })
+      `,
+      options: [{ ignore: ['foo'] }],
+    },
+    {
+      code: `
+        var UnusedComputedStringLiteralKeyStateTest = createReactClass({
+          getInitialState: function() {
+            return { ['foo']: 0 };
+          },
+          render: function() {
+            return <SomeComponent />;
+          }
+        })
+      `,
+      options: [{ ignore: ['foo'] }],
+    },
+    {
+      code: `
+        class UnusedCtorStateTest extends React.Component {
+          constructor() {
+            this.state = { foo: 0 };
+          }
+          render() {
+            return <SomeComponent />;
+          }
+        }
+      `,
+      options: [{ ignore: ['foo'] }],
+    },
+    {
+      code: `
+        class UnusedCtorStateTest extends React.Component {
+          constructor() {
+            this.state = { ['foo']: 0 };
+          }
+          render() {
+            return <SomeComponent />;
+          }
+        }
+      `,
+      options: [{ ignore: ['foo'] }],
     }
   )),
 
@@ -1616,5 +1668,61 @@ eslintTester.run('no-unused-state', rule, {
         'thisDestructStateDestructPropUnused',
       ]),
     },
+    {
+      code: `
+        var UnusedGetInitialStateTest = createReactClass({
+          getInitialState: function() {
+            return { foo: 0, dummy: 0 };
+          },
+          render: function() {
+            return <SomeComponent />;
+          }
+        })
+      `,
+      options: [{ ignore: ['foo'] }],
+      errors: getErrorMessages(['dummy']),
+    },
+    {
+      code: `
+        var UnusedGetInitialStateTest = createReactClass({
+          getInitialState: function() {
+            return { ['foo']: 0, ['dummy']: 0 };
+          },
+          render: function() {
+            return <SomeComponent />;
+          }
+        })
+      `,
+      options: [{ ignore: ['foo'] }],
+      errors: getErrorMessages(['dummy']),
+    },
+    {
+      code: `
+        class UnusedCtorStateTest extends React.Component {
+          constructor() {
+            this.state = { foo: 0, dummy: 0 };
+          }
+          render() {
+            return <SomeComponent />;
+          }
+        }
+      `,
+      options: [{ ignore: ['foo'] }],
+      errors: getErrorMessages(['dummy']),
+    },
+    {
+      code: `
+        class UnusedCtorStateTest extends React.Component {
+          constructor() {
+            this.state = { ['foo']: 0, ['dummy']: 0 };
+          }
+          render() {
+            return <SomeComponent />;
+          }
+        }
+      `,
+      options: [{ ignore: ['foo'] }],
+      errors: getErrorMessages(['dummy']),
+    },
   ]),
 });