Bug 1331081 - make the no-useless-parameters eslint rule report useless addEventListener false third parameter, r=jaws.

--HG--
extra : rebase_source : 9b2b156afacff5d1309c60a3620d061706cc303c

tools/lint/eslint/eslint-plugin-mozilla/lib/rules/no-useless-parameters.js

@@ -29,6 +29,16 @@ module.exports = function(context) {
         return;
       }
 
+      if ((callee.property.name === "addEventListener" ||
+           callee.property.name === "removeEventListener") &&
+          node.arguments.length === 3) {
+        let arg = node.arguments[2];
+        if (arg.type === "Literal" && arg.value === false) {
+          context.report(node, callee.property.name +
+                         "'s third parameter can be omitted when it's false.");
+        }
+      }
+
       if ((["getCharPref", "getBoolPref", "getIntPref", "clearUserPref"]
            .indexOf(callee.property.name) != -1) &&
           node.arguments.length > 1) {

tools/lint/eslint/eslint-plugin-mozilla/package.json

@@ -1,6 +1,6 @@
 {
   "name": "eslint-plugin-mozilla",
-  "version": "0.2.10",
+  "version": "0.2.11",
   "description": "A collection of rules that help enforce JavaScript coding standard in the Mozilla project.",
   "keywords": [
     "eslint",

tools/lint/eslint/eslint-plugin-mozilla/tests/no-useless-parameters.js

@@ -27,6 +27,11 @@ exports.runTest = function(ruleTester) {
       "Services.removeObserver('notification name', {});",
       "Services.io.newURI('http://example.com');",
       "Services.io.newURI('http://example.com', 'utf8');",
+      "elt.addEventListener('click', handler);",
+      "elt.addEventListener('click', handler, true);",
+      "elt.addEventListener('click', handler, {once: true});",
+      "elt.removeEventListener('click', handler);",
+      "elt.removeEventListener('click', handler, true);",
     ],
     invalid: [
       {
@@ -60,6 +65,14 @@ exports.runTest = function(ruleTester) {
       {
         code: "Services.io.newURI('http://example.com', 'utf8', null);",
         errors: callError("newURI's optional parameters passed as null.")
+      },
+      {
+        code: "elt.addEventListener('click', handler, false);",
+        errors: callError("addEventListener's third parameter can be omitted when it's false.")
+      },
+      {
+        code: "elt.removeEventListener('click', handler, false);",
+        errors: callError("removeEventListener's third parameter can be omitted when it's false.")
       }
     ]
   });