1 files changed, 130 insertions, 0 deletions
diff --git a/remote/cdp/Error.sys.mjs b/remote/cdp/Error.sys.mjs
new file mode 100644
index 0000000000..b047285649
--- /dev/null
+++ b/remote/cdp/Error.sys.mjs
@@ -0,0 +1,130 @@
+/* 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/. */
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  Log: "chrome://remote/content/shared/Log.sys.mjs",
+});
+
+ChromeUtils.defineLazyGetter(lazy, "logger", () =>
+  lazy.Log.get(lazy.Log.TYPES.CDP)
+);
+
+export class RemoteAgentError extends Error {
+  constructor(message = "", cause = undefined) {
+    cause = cause || message;
+    super(cause);
+
+    this.name = this.constructor.name;
+    this.message = message;
+    this.cause = cause;
+
+    this.notify();
+  }
+
+  notify() {
+    console.error(this);
+    lazy.logger.error(this.toString({ stack: true }));
+  }
+
+  toString({ stack = false } = {}) {
+    return RemoteAgentError.format(this, { stack });
+  }
+
+  static format(e, { stack = false } = {}) {
+    return formatError(e, { stack });
+  }
+
+  /**
+   * Takes a serialised CDP error and reconstructs it
+   * as a RemoteAgentError.
+   *
+   * The error must be of this form:
+   *
+   *     {"message": "TypeError: foo is not a function\n
+   *     execute@chrome://remote/content/cdp/sessions/Session.jsm:73:39\n
+   *     onMessage@chrome://remote/content/cdp/sessions/TabSession.jsm:65:20"}
+   *
+   * This approach has the notable deficiency that it cannot deal
+   * with causes to errors because of the unstructured nature of CDP
+   * errors.  A possible future improvement would be to extend the
+   * error serialisation to include discrete fields for each data
+   * property.
+   *
+   * @param {object} json
+   *     CDP error encoded as a JSON object, which must have a
+   *     "message" field, where the first line will make out the error
+   *     message and the subsequent lines the stacktrace.
+   *
+   * @returns {RemoteAgentError}
+   */
+  static fromJSON(json) {
+    const [message, ...stack] = json.message.split("\n");
+    const err = new RemoteAgentError();
+    err.message = message.slice(0, -1);
+    err.stack = stack.map(s => s.trim()).join("\n");
+    err.cause = null;
+    return err;
+  }
+}
+
+/**
+ * A fatal error that it is not possible to recover from
+ * or send back to the client.
+ *
+ * Constructing this error will force the application to quit.
+ */
+export class FatalError extends RemoteAgentError {
+  constructor(...args) {
+    super(...args);
+    this.quit();
+  }
+
+  notify() {
+    lazy.logger.fatal(this.toString({ stack: true }));
+  }
+
+  quit(mode = Ci.nsIAppStartup.eForceQuit) {
+    Services.startup.quit(mode);
+  }
+}
+
+/** When an operation is not yet implemented. */
+export class UnsupportedError extends RemoteAgentError {}
+
+/** The requested remote method does not exist. */
+export class UnknownMethodError extends RemoteAgentError {
+  constructor(domain, command = null) {
+    if (command) {
+      super(`${domain}.${command}`);
+    } else {
+      super(domain);
+    }
+  }
+}
+
+function formatError(error, { stack = false } = {}) {
+  const els = [];
+
+  els.push(error.name);
+  if (error.message) {
+    els.push(": ");
+    els.push(error.message);
+  }
+
+  if (stack && error.stack) {
+    els.push(":\n");
+
+    const stack = error.stack.trim().split("\n");
+    els.push(stack.map(line => `\t${line}`).join("\n"));
+
+    if (error.cause) {
+      els.push("\n");
+      els.push("caused by: " + formatError(error.cause, { stack }));
+    }
+  }
+
+  return els.join("");
+}