1 files changed, 90 insertions, 0 deletions
diff --git a/remote/shared/messagehandler/Errors.sys.mjs b/remote/shared/messagehandler/Errors.sys.mjs
new file mode 100644
index 0000000000..69c65acd09
--- /dev/null
+++ b/remote/shared/messagehandler/Errors.sys.mjs
@@ -0,0 +1,90 @@
+/* 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/. */
+
+import { RemoteError } from "chrome://remote/content/shared/RemoteError.sys.mjs";
+
+class MessageHandlerError extends RemoteError {
+  /**
+   * @param {(string|Error)=} x
+   *     Optional string describing error situation or Error instance
+   *     to propagate.
+   */
+  constructor(x) {
+    super(x);
+    this.name = this.constructor.name;
+    this.status = "message handler error";
+
+    // Error's ctor does not preserve x' stack
+    if (typeof x?.stack !== "undefined") {
+      this.stack = x.stack;
+    }
+  }
+
+  get isMessageHandlerError() {
+    return true;
+  }
+
+  /**
+   * @returns {Object<string, string>}
+   *     JSON serialisation of error prototype.
+   */
+  toJSON() {
+    return {
+      error: this.status,
+      message: this.message || "",
+      stacktrace: this.stack || "",
+    };
+  }
+
+  /**
+   * Unmarshals a JSON error representation to the appropriate MessageHandler
+   * error type.
+   *
+   * @param {Object<string, string>} json
+   *     Error object.
+   *
+   * @returns {Error}
+   *     Error prototype.
+   */
+  static fromJSON(json) {
+    if (typeof json.error == "undefined") {
+      let s = JSON.stringify(json);
+      throw new TypeError("Undeserialisable error type: " + s);
+    }
+    if (!STATUSES.has(json.error)) {
+      throw new TypeError("Not of MessageHandlerError descent: " + json.error);
+    }
+
+    let cls = STATUSES.get(json.error);
+    let err = new cls();
+    if ("message" in json) {
+      err.message = json.message;
+    }
+    if ("stacktrace" in json) {
+      err.stack = json.stacktrace;
+    }
+    return err;
+  }
+}
+
+/**
+ * A command could not be handled by the message handler network.
+ */
+class UnsupportedCommandError extends MessageHandlerError {
+  constructor(message) {
+    super(message);
+    this.status = "unsupported message handler command";
+  }
+}
+
+const STATUSES = new Map([
+  ["message handler error", MessageHandlerError],
+  ["unsupported message handler command", UnsupportedCommandError],
+]);
+
+/** @namespace */
+export const error = {
+  MessageHandlerError,
+  UnsupportedCommandError,
+};