[Fix] no-unused-state: false negative on using state of non-lifecycle

Author: chiawendt

lib/rules/no-unused-state.js

@@ -101,7 +101,7 @@ module.exports = {
           parent &&
           parent.type === 'MethodDefinition' && (
             parent.static && parent.key.name === 'getDerivedStateFromProps' ||
-            classMethods.indexOf(parent.key.name !== -1)
+            classMethods.indexOf(parent.key.name) !== -1
           ) &&
           parent.value.type === 'FunctionExpression' &&
           parent.value.params[1] &&

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

@@ -1059,6 +1059,26 @@ eslintTester.run('no-unused-state', rule, {
       errors: getErrorMessages(['foo']),
       parser: parsers.BABEL_ESLINT
     },
+    {
+      code: `class UseStateParameterOfNonLifecycleTest extends Component {
+        constructor(props) {
+          super(props);
+          this.state = {
+            foo: 123,
+          };
+        }
+        nonLifecycle(someProps, someState) {
+          doStuff(someState.foo)
+        }
+        render() {
+          return (
+            <SomeComponent />
+          );
+        }
+      }`,
+      errors: getErrorMessages(['foo']),
+      parser: parsers.BABEL_ESLINT
+    },
     {
       code: `class MissingStateParameterTest extends Component {
         constructor(props) {