gecko/toolkit/devtools/DevToolsUtils.js

/* 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";

/* General utilities used throughout devtools. */

/**
 * Turn the error |aError| into a string, without fail.
 */
this.safeErrorString = function safeErrorString(aError) {
  try {
    let errorString = aError.toString();
    if (typeof errorString === "string") {
      // Attempt to attach a stack to |errorString|. If it throws an error, or
      // isn't a string, don't use it.
      try {
        if (aError.stack) {
          let stack = aError.stack.toString();
          if (typeof stack === "string") {
            errorString += "\nStack: " + stack;
          }
        }
      } catch (ee) { }

      return errorString;
    }
  } catch (ee) { }

  return "<failed trying to find error description>";
}

/**
 * Report that |aWho| threw an exception, |aException|.
 */
this.reportException = function reportException(aWho, aException) {
  let msg = aWho + " threw an exception: " + safeErrorString(aException);

  dump(msg + "\n");

  if (Components.utils.reportError) {
    /*
     * Note that the xpcshell test harness registers an observer for
     * console messages, so when we're running tests, this will cause
     * the test to quit.
     */
    Components.utils.reportError(msg);
  }
}

/**
 * Given a handler function that may throw, return an infallible handler
 * function that calls the fallible handler, and logs any exceptions it
 * throws.
 *
 * @param aHandler function
 *      A handler function, which may throw.
 * @param aName string
 *      A name for aHandler, for use in error messages. If omitted, we use
 *      aHandler.name.
 *
 * (SpiderMonkey does generate good names for anonymous functions, but we
 * don't have a way to get at them from JavaScript at the moment.)
 */
this.makeInfallible = function makeInfallible(aHandler, aName) {
  if (!aName)
    aName = aHandler.name;

  return function (/* arguments */) {
    try {
      return aHandler.apply(this, arguments);
    } catch (ex) {
      let who = "Handler function";
      if (aName) {
        who += " " + aName;
      }
      reportException(who, ex);
    }
  }
}