Bug 1430923 - Handle EXPORTED_SYMBOLS in ESLint to help define globals in jsm files, and disallow 'let EXPORTED_SYMBOLS = '. r=mossop

MozReview-Commit-ID: 5abfpM8EAEL

--HG--
extra : rebase_source : b266018a3754459aa8628217232f86e1a56c00b7

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

@@ -68,7 +68,15 @@ module.exports = {
       "browser": false,
       "mozilla/jsm": true
     },
-    "files": "**/*.jsm"
+    "files": "**/*.jsm",
+    "rules": {
+      "mozilla/mark-exported-symbols-as-used": "error"
+      // "no-unused-vars": ["error", {
+      //   "args": "none",
+      //   "vars": "all",
+      //   "varsIgnorePattern": "^Cc|Ci|Cu|Cr|EXPORTED_SYMBOLS"
+      // }]
+    }
   }],
 
   "parserOptions": {

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

@@ -40,6 +40,7 @@ module.exports = {
       require("../lib/rules/import-content-task-globals"),
     "import-globals": require("../lib/rules/import-globals"),
     "import-headjs-globals": require("../lib/rules/import-headjs-globals"),
+    "mark-exported-symbols-as-used": require("../lib/rules/mark-exported-symbols-as-used"),
     "mark-test-function-used": require("../lib/rules/mark-test-function-used"),
     "no-aArgs": require("../lib/rules/no-aArgs"),
     "no-arbitrary-setTimeout": require("../lib/rules/no-arbitrary-setTimeout"),

tools/lint/eslint/eslint-plugin-mozilla/lib/rules/mark-exported-symbols-as-used.js

@@ -0,0 +1,76 @@
+/**
+ * @fileoverview Simply marks exported symbols as used. Designed for use in
+ * .jsm files only.
+ *
+ * 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";
+
+function markArrayElementsAsUsed(context, node, expression) {
+  if (expression.type != "ArrayExpression") {
+    context.report({
+      node,
+      message: "Unexpected assignment of non-Array to EXPORTED_SYMBOLS"
+    });
+    return;
+  }
+
+  for (let element of expression.elements) {
+    context.markVariableAsUsed(element.value);
+  }
+}
+
+// -----------------------------------------------------------------------------
+// Rule Definition
+// -----------------------------------------------------------------------------
+
+module.exports = function(context) {
+  // Ignore assignments not in the global scope, e.g. where special module
+  // definitions are required due to having different ways of importing files,
+  // e.g. osfile.
+  function isGlobalScope() {
+    return !context.getScope().upper;
+  }
+
+  // ---------------------------------------------------------------------------
+  // Public
+  // ---------------------------------------------------------------------------
+
+  return {
+    AssignmentExpression(node, parents) {
+      if (node.operator === "=" &&
+          node.left.type === "MemberExpression" &&
+          node.left.object.type === "ThisExpression" &&
+          node.left.property.name === "EXPORTED_SYMBOLS" &&
+          isGlobalScope()) {
+        markArrayElementsAsUsed(context, node, node.right);
+      }
+    },
+
+    VariableDeclaration(node, parents) {
+      if (!isGlobalScope()) {
+        return;
+      }
+
+      for (let item of node.declarations) {
+        if (item.id &&
+            item.id.type == "Identifier" &&
+            item.id.name === "EXPORTED_SYMBOLS") {
+          if (node.kind === "let") {
+            // The use of 'let' isn't allowed as the lexical scope may die after
+            // the script executes.
+            context.report({
+              node,
+              message: "EXPORTED_SYMBOLS cannot be declared via `let`. Use `var` or `this.EXPORTED_SYMBOLS =`"
+            });
+          }
+
+          markArrayElementsAsUsed(context, node, item.init);
+        }
+      }
+    }
+  };
+};

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

@@ -1,6 +1,6 @@
 {
   "name": "eslint-plugin-mozilla",
-  "version": "0.5.0",
+  "version": "0.6.0",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {

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

@@ -1,6 +1,6 @@
 {
   "name": "eslint-plugin-mozilla",
-  "version": "0.5.0",
+  "version": "0.6.0",
   "description": "A collection of rules that help enforce JavaScript coding standard in the Mozilla project.",
   "keywords": [
     "eslint",

tools/lint/eslint/eslint-plugin-mozilla/tests/mark-exported-symbols-as-used.js

@@ -0,0 +1,36 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+// ------------------------------------------------------------------------------
+// Requirements
+// ------------------------------------------------------------------------------
+
+var rule = require("../lib/rules/mark-exported-symbols-as-used");
+var RuleTester = require("eslint/lib/testers/rule-tester");
+
+const ruleTester = new RuleTester({ parserOptions: { ecmaVersion: 6 } });
+
+// ------------------------------------------------------------------------------
+// Tests
+// ------------------------------------------------------------------------------
+
+function invalidCode(code, type, message) {
+  return {code, errors: [{message, type}]};
+}
+
+ruleTester.run("mark-exported-symbols-as-used", rule, {
+  valid: [
+    "var EXPORTED_SYMBOLS = ['foo'];",
+    "this.EXPORTED_SYMBOLS = ['foo'];"
+  ],
+  invalid: [
+    invalidCode("let EXPORTED_SYMBOLS = ['foo'];", "VariableDeclaration",
+                "EXPORTED_SYMBOLS cannot be declared via `let`. Use `var` or `this.EXPORTED_SYMBOLS =`"),
+    invalidCode("var EXPORTED_SYMBOLS = 'foo';", "VariableDeclaration",
+                "Unexpected assignment of non-Array to EXPORTED_SYMBOLS"),
+    invalidCode("this.EXPORTED_SYMBOLS = 'foo';", "AssignmentExpression",
+                "Unexpected assignment of non-Array to EXPORTED_SYMBOLS")
+  ]
+});