February 27, 2009

Automatic Bug Reporting for Firefox Extensions

We want to make Ubiquity awesome at reporting errors. In our original release, a transparent message with JavaScript exception information was displayed, which wasn’t very useful to the average user, and was downright annoying when dozens of exceptions were logged in the same instant.

At present, running a command that raises an error just results in that message being logged to the JS Error console, which very few people know how to access—so most people are left scratching their heads and wondering why their command is taking so long to run.

For the next release of Ubiquity, we’re going to be trying something more user-friendly: if a command encounters an error, a transparent message will be displayed telling the user that it didn’t work. The message will also recommend using the “report-bug” command to send information about the bug to the Ubiquity team. If the user decides to run this command, a page is opened that looks like this:

Aside from inviting the user to describe their problem, a lot of information is included about their system: what OS they’re using, what extensions and plugins they have installed, what recent exceptions were thrown, and so forth. We’re hoping this will lower the barrier to entry both for receiving and providing technical support, since most of the information needed to describe and investigate a problem is contained in a single link.

We don’t yet have an interface for browsing existing bugs, but we do have a display for viewing them. It looks pretty similar to the page for submitting a bug:

One interesting aspect of our bug reporting system is that we’re not using numbers to identify bug reports: they get big fast as many reports are submitted, and big numbers are hard to remember. Instead, we’re mashing two random words from the dictionary together. For instance, the first bug I reported using this system was called anaphorically-spinach.

Under The Hood

The bug reporting system is pretty lightweight: mostly it’s just static HTML/JavaScript code that talks to a web service that’s implemented in under 100 lines of Python. The actual bug report is just a JSON object, and is deposited into a CouchDB server.

The big advantage of using CouchDB here is that we’ll be able to easily create really rich queries using plain old JavaScript. For instance, here’s a query that shows all reported error messages that contain the text “Invalid chrome URI”. It won’t be hard to create complex queries that, for instance, give us all the bug reports in which the user had a certain extension installed and had a command crash at a particular line in a particular file.

A Public Asset

Right now all reports are submitted to the public domain, and as such the report database is a public asset; users are informed of this before they submit the bug, and encouraged to look at the additional data that’s being sent with their report to ensure that there’s nothing sensitive in there. In the future, it’d be nice to allow the user to click on any parts of the data that are personally identifying, so that they can submit a version of the report that masks out the sensitive information.


The bug report system has been designed to be decoupled from Ubiquity itself. For instance, the report viewing application is designed as a reusable JavaScript component, so it should ultimately be easy to embed into any web page. In other words, it should be easy to use as a bug reporting mechanism for any Firefox extension—and possibly for any web application in general. If you’re interested in adding the component to your own project, please let us know; the code is still a work-in-progress, and any contributions or comments are appreciated.

© Atul Varma 2021