tools: add lint rule to enforce timer arguments

Add a custom ESLint rule to require that setTimeout() and setInterval()
get called with at least two arguments. This prevents omitting the
duration or interval.

Author: Trott

.eslintrc

@@ -128,6 +128,7 @@ rules:
   assert-fail-single-argument: 2
   assert-throws-arguments: [2, { requireTwo: false }]
   new-with-error: [2, Error, RangeError, TypeError, SyntaxError, ReferenceError]
+  timer-arguments: 2
 
 # Global scoped method and vars
 globals:

tools/eslint-rules/timer-arguments.js

@@ -0,0 +1,25 @@
+/**
+ * @fileoverview Require at least two arguments when calling setTimeout() or
+ * setInterval().
+ * @author Rich Trott
+ */
+'use strict';
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+function isTimer(name) {
+  return ['setTimeout', 'setInterval'].includes(name);
+}
+
+module.exports = function(context) {
+  return {
+    'CallExpression': function(node) {
+      const name = node.callee.name;
+      if (isTimer(name) && node.arguments.length < 2) {
+        context.report(node, `${name} must have at least 2 arguments`);
+      }
+    }
+  };
+};