Allow useEffect(fn, undefined) in react-hooks/exhaustive-deps.

Author: cpojer

packages/eslint-plugin-react-hooks/__tests__/ESLintRuleExhaustiveDeps-test.js

@@ -1452,6 +1452,15 @@ const tests = {
         }
       `,
     },
+    {
+      code: normalizeIndent`
+        function MyComponent() {
+          useEffect(() => {
+            console.log('banana banana banana');
+          }, undefined);
+        }
+      `,
+    },
   ],
   invalid: [
     {

packages/eslint-plugin-react-hooks/src/ExhaustiveDeps.js

@@ -1161,7 +1161,12 @@ export default {
       const callback = node.arguments[callbackIndex];
       const reactiveHook = node.callee;
       const reactiveHookName = getNodeWithoutReactNamespace(reactiveHook).name;
-      const declaredDependenciesNode = node.arguments[callbackIndex + 1];
+      const maybeNode = node.arguments[callbackIndex + 1];
+      const declaredDependenciesNode =
+        maybeNode &&
+        !(maybeNode.type === 'Identifier' && maybeNode.name === 'undefined')
+          ? maybeNode
+          : undefined;
       const isEffect = /Effect($|[^a-z])/g.test(reactiveHookName);
 
       // Check whether a callback is supplied. If there is no callback supplied