Create src/util/deprecated-extension-storage.js

src/util/deprecated-extension-storage.js

@@ -0,0 +1,31 @@
+/**
+ * @overview
+ * Utility for creating a proxy object that warns extension authors to not use the runtime.extensionStorage
+ * or target.extensionStorage APIs, as they're both deprecated.
+ */
+
+/**
+ * A set of extensions that have been warned. A set is used for performance reasons.
+ */
+const WARNED_EXTENSIONS = new Set();
+
+/**
+ * Creates the actual proxy object.
+ * @param {object.<string, any>} [default_content] Used by the deserializer to set the values of extensionStorage.
+ */
+const ExtensionStorage = (default_content = {}) => {
+  return new Proxy(
+    default_content,
+    {
+      set: function (target, key, value) {
+        if (!WARNED_EXTENSIONS.has(key)) {
+            console.warn("extensionStorage APIs are deprecated. Please avoid using them in your extensions.");
+            WARNED_EXTENSIONS.add(key);
+        }
+        return target[key] = value;
+      },
+    }
+  );
+};
+
+module.exports = ExtensionStorage;