extensions/renderer/resources/uncaught_exception_handler.js

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 // Handles uncaught exceptions thrown by extensions. By default this is to
   6 // log an error message, but tests may override this behaviour.
   7 var handler = function(message, e) {
   8   console.error(message);
   9 };
  10
  11 /**
  12  * Append the error description and stack trace to |message|.
  13  *
  14  * @param {string} message - The prefix of the error message.
  15  * @param {Error|*} e - The thrown error object. This object is potentially
  16  *   unsafe, because it could be generated by an extension.
  17  * @param {string=} priorStackTrace - The stack trace to be appended to the
  18  *   error message. This stack trace must not include stack frames of |e.stack|,
  19  *   because both stack traces are concatenated. Overlapping stack traces will
  20  *   confuse extension developers.
  21  * @return {string} The formatted error message.
  22  */
  23 function formatErrorMessage(message, e, priorStackTrace) {
  24   if (e)
  25     message += ': ' + safeErrorToString(e, false);
  26
  27   var stack;
  28   try {
  29     // If the stack was set, use it.
  30     // |e.stack| could be void in the following common example:
  31     // throw "Error message";
  32     stack = $String.self(e && e.stack);
  33   } catch (e) {}
  34
  35   // If a stack is not provided, capture a stack trace.
  36   if (!priorStackTrace && !stack)
  37     stack = getStackTrace();
  38
  39   stack = filterExtensionStackTrace(stack);
  40   if (stack)
  41     message += '\n' + stack;
  42
  43   // If an asynchronouse stack trace was set, append it.
  44   if (priorStackTrace)
  45     message += '\n' + priorStackTrace;
  46
  47   return message;
  48 }
  49
  50 function filterExtensionStackTrace(stack) {
  51   if (!stack)
  52     return '';
  53   // Remove stack frames in the stack trace that weren't associated with the
  54   // extension, to not confuse extension developers with internal details.
  55   stack = $String.split(stack, '\n');
  56   stack = $Array.filter(stack, function(line) {
  57     return $String.indexOf(line, 'chrome-extension://') >= 0;
  58   });
  59   return $Array.join(stack, '\n');
  60 }
  61
  62 function getStackTrace() {
  63   var e = {};
  64   $Error.captureStackTrace(e, getStackTrace);
  65   return e.stack;
  66 }
  67
  68 function getExtensionStackTrace() {
  69   return filterExtensionStackTrace(getStackTrace());
  70 }
  71
  72 /**
  73  * Convert an object to a string.
  74  *
  75  * @param {Error|*} e - A thrown object (possibly user-supplied).
  76  * @param {boolean=} omitType - Whether to try to serialize |e.message| instead
  77  *   of |e.toString()|.
  78  * @return {string} The error message.
  79  */
  80 function safeErrorToString(e, omitType) {
  81   try {
  82     return $String.self(omitType && e.message || e);
  83   } catch (e) {
  84     // This error is exceptional and could be triggered by
  85     // throw {toString: function() { throw 'Haha' } };
  86     return '(cannot get error message)';
  87   }
  88 }
  89
  90 /**
  91  * Formats the error message and invokes the error handler.
  92  *
  93  * @param {string} message - Error message prefix.
  94  * @param {Error|*} e - Thrown object.
  95  * @param {string=} priorStackTrace - Error message suffix.
  96  * @see formatErrorMessage
  97  */
  98 exports.handle = function(message, e, priorStackTrace) {
  99   message = formatErrorMessage(message, e, priorStackTrace);
 100   handler(message, e);
 101 };
 102
 103 // |newHandler| A function which matches |handler|.
 104 exports.setHandler = function(newHandler) {
 105   handler = newHandler;
 106 };
 107
 108 exports.getStackTrace = getStackTrace;
 109 exports.getExtensionStackTrace = getExtensionStackTrace;
 110 exports.safeErrorToString = safeErrorToString;