Bug 1339461 - add an eslint rule to detect when indexOf should be replaced with includes, r=Standard8.

browser/components/places/tests/browser/browser_sort_in_library.js

@@ -79,7 +79,7 @@ function checkSort(aTree, aSortingMode, aSortingAnno) {
   // Check sortingAnnotation, but only if sortingMode is ANNOTATION.
   if ([Ci.nsINavHistoryQueryOptions.SORT_BY_ANNOTATION_ASCENDING,
        Ci.nsINavHistoryQueryOptions.SORT_BY_ANNOTATION_DESCENDING].
-      indexOf(aSortingMode) >= 0) {
+      includes(aSortingMode)) {
     is(res.sortingAnnotation, aSortingAnno,
        "column should now have sorting annotation " + aSortingAnno);
   }

tools/lint/docs/linters/eslint-plugin-mozilla.rst

@@ -274,6 +274,11 @@ use-ownerGlobal
 
 Require .ownerGlobal instead of .ownerDocument.defaultView.
 
+use-includes-instead-of-indexOf
+-------------------------------
+
+Use .includes instead of .indexOf to check if something is in an array or string.
+
 use-services
 ------------
 

tools/lint/eslint/eslint-plugin-mozilla/lib/configs/recommended.js

@@ -171,6 +171,7 @@ module.exports = {
     "mozilla/no-useless-removeEventListener": "error",
     "mozilla/use-chromeutils-import": "error",
     "mozilla/use-default-preference-values": "error",
+    "mozilla/use-includes-instead-of-indexOf": "error",
     "mozilla/use-ownerGlobal": "error",
     "mozilla/use-services": "error",
 

tools/lint/eslint/eslint-plugin-mozilla/lib/index.js

@@ -61,6 +61,7 @@ module.exports = {
     "use-default-preference-values":
       require("../lib/rules/use-default-preference-values"),
     "use-ownerGlobal": require("../lib/rules/use-ownerGlobal"),
+    "use-includes-instead-of-indexOf": require("../lib/rules/use-includes-instead-of-indexOf"),
     "use-services": require("../lib/rules/use-services"),
     "var-only-at-top-level": require("../lib/rules/var-only-at-top-level")
   },
@@ -87,6 +88,7 @@ module.exports = {
     "use-chromeutils-import": "off",
     "use-default-preference-values": "off",
     "use-ownerGlobal": "off",
+    "use-includes-instead-of-indexOf": "off",
     "use-services": "off",
     "var-only-at-top-level": "off"
   }

tools/lint/eslint/eslint-plugin-mozilla/lib/rules/use-includes-instead-of-indexOf.js

@@ -0,0 +1,42 @@
+/**
+ * @fileoverview Use .includes instead of .indexOf
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+"use strict";
+
+// -----------------------------------------------------------------------------
+// Rule Definition
+// -----------------------------------------------------------------------------
+
+module.exports = function(context) {
+
+  // ---------------------------------------------------------------------------
+  // Public
+  //  --------------------------------------------------------------------------
+
+  return {
+    "BinaryExpression": function(node) {
+      if (node.left.type != "CallExpression" ||
+          node.left.callee.type != "MemberExpression" ||
+          node.left.callee.property.type != "Identifier" ||
+          node.left.callee.property.name != "indexOf") {
+        return;
+      }
+
+      if ((["!=", "!==", "==", "==="].includes(node.operator) &&
+           node.right.type == "UnaryExpression" &&
+           node.right.operator == "-" &&
+           node.right.argument.type == "Literal" &&
+           node.right.argument.value == 1) ||
+          ([">=", "<"].includes(node.operator) &&
+           node.right.type == "Literal" &&
+           node.right.value == 0)) {
+        context.report(node, "use .includes instead of .indexOf");
+      }
+    }
+  };
+};

tools/lint/eslint/eslint-plugin-mozilla/tests/use-includes-instead-of-indexOf.js

@@ -0,0 +1,38 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+// ------------------------------------------------------------------------------
+// Requirements
+// ------------------------------------------------------------------------------
+
+var rule = require("../lib/rules/use-includes-instead-of-indexOf");
+var RuleTester = require("eslint/lib/testers/rule-tester");
+
+const ruleTester = new RuleTester({ parserOptions: { ecmaVersion: 6 } });
+
+// ------------------------------------------------------------------------------
+// Tests
+// ------------------------------------------------------------------------------
+
+function invalidCode(code) {
+  let message = "use .includes instead of .indexOf";
+  return {code, errors: [{message, type: "BinaryExpression"}]};
+}
+
+ruleTester.run("use-includes-instead-of-indexOf", rule, {
+  valid: [
+    "let a = foo.includes(bar);",
+    "let a = foo.indexOf(bar) > 0;",
+    "let a = foo.indexOf(bar) != 0;"
+  ],
+  invalid: [
+    invalidCode("let a = foo.indexOf(bar) >= 0;"),
+    invalidCode("let a = foo.indexOf(bar) != -1;"),
+    invalidCode("let a = foo.indexOf(bar) !== -1;"),
+    invalidCode("let a = foo.indexOf(bar) == -1;"),
+    invalidCode("let a = foo.indexOf(bar) === -1;"),
+    invalidCode("let a = foo.indexOf(bar) < 0;")
+  ]
+});