tools: simplify prefer-assert-methods rule

PR-URL: #17572
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>

tools/eslint-rules/prefer-assert-methods.js

@@ -1,15 +1,8 @@
 'use strict';
 
-function isAssert(node) {
-  return node.expression &&
-    node.expression.type === 'CallExpression' &&
-    node.expression.callee &&
-    node.expression.callee.name === 'assert';
-}
-
-function getFirstArg(expression) {
-  return expression.arguments && expression.arguments[0];
-}
+const astSelector = 'ExpressionStatement[expression.type="CallExpression"]' +
+                    '[expression.callee.name="assert"]' +
+                    '[expression.arguments.0.type="BinaryExpression"]';
 
 function parseError(method, op) {
   return `'assert.${method}' should be used instead of '${op}'`;
@@ -24,15 +17,11 @@ const preferedAssertMethod = {
 
 module.exports = function(context) {
   return {
-    ExpressionStatement(node) {
-      if (isAssert(node)) {
-        const arg = getFirstArg(node.expression);
-        if (arg && arg.type === 'BinaryExpression') {
-          const assertMethod = preferedAssertMethod[arg.operator];
-          if (assertMethod) {
-            context.report(node, parseError(assertMethod, arg.operator));
-          }
-        }
+    [astSelector]: function(node) {
+      const arg = node.expression.arguments[0];
+      const assertMethod = preferedAssertMethod[arg.operator];
+      if (assertMethod) {
+        context.report(node, parseError(assertMethod, arg.operator));
       }
     }
   };