Hunting the Shmoo

Following up last week’s post on some mach try fundamentals, I figured it would be worth posting some actual concrete tips and tricks. So without further ado, here are some things you can do with ./mach try you may not have known about in rapid fire format.

There is a lot of confusion around mach try. People frequently ask “How do I get task X in mach try fuzzy?” or “How can I avoid getting backed out?”. This post is not so much a tip, rather an explanation around how mach try works and its relationship to the CI system (taskgraph). Armed with this knowledge, I hope you’ll be able to use mach try a little more effectively.

It’s no secret that I’m not a fan of try syntax, it’s a topic I’ve blogged about on several occasions before. Today, I’m pleased to announce that there’s a real alternative now landed on mozilla-central. It works on all platforms with mercurial and git. For those who just like to dive in:

$ mach mercurial-setup --update  # only if using hg
$ mach try fuzzy

This will prompt you to install fzf. After bootstrapping is finished, you’ll enter an interface populated with a list of all possible taskcluster tasks. Start typing and the list will be filtered down using a fuzzy matching algorithm. I won’t go into details on how to use this tool in this blog post, for that see:

$ mach try fuzzy --help  # or
$ man fzf

I’ve previously blogged about why I believe try syntax is an antiquated development process that should be replaced with something more modern and flexible. What follows is a series of ideas that I’m trying to convert into a concrete plan of action to bring this about. This is not an Intent to Implement or anything like that, but my hope is that this outline is detailed enough that it could be used as a solid starting point by someone with enough time and motivation to work on it.

Today marks the 5 year anniversary of try syntax. For the uninitiated, try syntax is a string that you put into your commit message which a parser then uses to determine the set of builds and tests to run on your try push. A common try syntax might look like this:

try: -b o -p linux -u mochitest -t none

Since inception, it has been a core part of the Mozilla development workflow. For many years it has served us well, and even today it serves us passably. But it is almost time for try syntax to don the wooden overcoat, and this post will explain why.