1 files changed, 83 insertions, 0 deletions
diff --git a/tools/lint/eslint/eslint-plugin-mozilla/lib/rules/mark-exported-symbols-as-used.js b/tools/lint/eslint/eslint-plugin-mozilla/lib/rules/mark-exported-symbols-as-used.js
new file mode 100644
index 0000000000..c535a54a16
--- /dev/null
+++ b/tools/lint/eslint/eslint-plugin-mozilla/lib/rules/mark-exported-symbols-as-used.js
@@ -0,0 +1,83 @@
+/**
+ * @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);
+  }
+  // Also mark EXPORTED_SYMBOLS as used.
+  context.markVariableAsUsed("EXPORTED_SYMBOLS");
+}
+
+// -----------------------------------------------------------------------------
+// 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);
+        }
+      }
+    },
+  };
+};