Engineering Effectiveness Newsletter (September 2021 Edition)

Welcome to the September edition of the Engineering Effectiveness Newsletter! The Engineering Effectiveness org makes it easy to develop, test and release Mozilla software at scale. See below for some highlights, then read on for more detailed info!



  • Luni-4
  • Alex Lopez
  • masterwayz

Detailed Project Updates

Bugzilla and Bugbug

Build System and Mach Environment

  • Alex Lopez simplified Mach commands into top-level module functions, removing the previous class-inheritance complexity and boilerplate. This involved updating all existing Mach commands, which was a significant undertaking. Thanks for all the hard work over the months to land this Alex!
  • Mitch enhanced usage of system python packages to validate against in-tree requirements
  • Mitch made the vendoring of python packages reproducible. Now, other than for a few explicit exceptions, CI will warn when vendored packages are modified in-tree. This ensures that the “==” specified matches the vendored source files.
  • Welcome to Alex Hochheiden who joins the build team this week!

CI and Treeherder

Crash Management

Lint, Static Analysis and Code Coverage


  • Support for XFA forms is enabled starting from Firefox 93
    • XFA is used by some governments and large organizations like banks
    • You can now apply for a fish export license in Canada without leaving Firefox!

Phabricator , moz-phab, and Lando

  • Zeid added custom warning support in Lando. New API endpoints can be used by any service (including code review bot, for example) to add landing warnings to specific revisions/diffs.
  • Zeid added the ability for users to cancel deferred jobs (i.e. jobs that were submitted but could not land because of tree closure)

Release Engineering and Management

  • Welcome to Heitor Neiva who joins Release Engineering this week!

Thanks for reading and see you next month!