thunderbird

Welcome to the Q1 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!

Highlights

Suhaib Integrated Review Helper with Phabricator and moz-phab making AI-powered code review quick and simple.
Connor Sheehan implemented ETL from Lando to STMO, which allows us to get better visibility into lando's performance and usage.
Firefox 150 will ship with new PDF editing features completed by Calixte, letting users delete, copy, move, and export pages to a new PDF.

Detailed Project Updates

AI for Development

Suhaib Mujahid integrated Review Helper with Phabricator, enabling AI-powered code review directly from patches by clicking a "Request AI Review" button, allowing it to analyze the patch and post comments with any findings.
Suhaib Mujahid extended moz-phab to support requesting an AI review at patch submission time, enabling contributors to trigger Review Helper analysis directly from the command line via moz-phab --ai.

Bugzilla

Marco trained a new model in bugbug to detect bugs that are accessibility-related and missing the "access" keyword, to bring them to the attention of the accessibility team
- First bugs found: Bug 2026654, Bug 2026647, Bug 2025992
Two fixes from dkl to improve the reliability of the background bot that syncs Phabricator revisions with Bugzilla bugs.
Kohei updated the markdown comment editor now intelligently handles pasting URLs. When you paste a URL while text is selected, it automatically formats it as a markdown link "selected text".
Kohei has also done significant improvements to the Guided Bug Entry page for new Bugzilla pages that should be going live soon.

Build System and Mach Environment

Better scheduling of rust dependencies through Bug 2011880 leads to ~1m saving in build time for opt build with hot cache.
Warning flags can no longer be added directly to CFLAGS or CXXFLAGS in moz.build, they have to go in COMPILE_FLAGS["WARNINGS_CXXFLAGS"] (resp. COMPILE_FLAGS["WARNINGS_CFLAGS"]) (see Bug 1986258)

Firefox-CI, Taskcluster and Treeherder

Matt Boris upgraded FxCI to use RabbitMQ quorum queues and upgraded pulse to the latest available version for performance, security, and reliability.
Abhishek Madan migrated schema validation from Voluptuous to msgspec across taskgraph, mozilla-taskgraph, and firefox, resulting in a 30% improvement to decision task times.
- Bug for conversion in Firefox, PR in Taskgraph, PR in Mozilla-Taskgraph
Abhishek Madan moved Firefox from a vendored copy of taskgraph to PyPI installs at setup time, enabling support for packages that include compiled components.
- Patch stack
Andrew Halberstadt made lots of progress migrating CI to Github, currently being used by mozilla/enterprise-firefox:
- Support for actions
- Fixed index and Treeherder routes
- Support for mach try
- Added pull_request_number as a parameter
Andrew Halberstadt wrote a patch implementing the ability for the Taskcluster Github service to trigger hooks listed in .taskcluster.yml files. This will pave the way to share cross-project workflows and simplify in-repo configuration.
Cameron Dawson upgraded major frontend libraries of Treeherder

Lint, Static Analysis and Code Coverage

New linter for header guards, through bug 2009182, triggered by mach lint --linter header-guards . It enforces our code style.
A limited subset of clang-tidy's static analysis is now run and enforced on our whole codebase. It is also reported during review on phabricator (see Bug 2023518 and related bugs)
ESLint and Prettier have been updated to the latest versions.
- This included a fix for eslint-plugin-jsdoc check-property-names rule which was raising some false-positives in firefox-main.
eslint-env comments are being removed as ESLint v9 does not support them (use eslint-file-globals.config.mjs instead). ESLint v10 (currently in rc) will raise errors for them.
More eslint-plugin-jsdoc rules have been enabled across the whole tree. These are the ones relating to valid-jsdoc. A few remain, but will need work by teams to fix the failur
The "Black" python formatter has now been replaced by "Ruff".
Marco greatly simplified the code coverage infrastructure, getting rid of two Heroku services, a frontend service, and a lot of code. The code coverage official UI is now Searchfox.
Marco added a new mach command ("./mach coverage-report") to generate a coverage report from a push. The command is documented on the code coverage page in the Firefox source docs.
Teklia added added support for Github pull requests to Code Review Bot (prototype)

PDF.js

Calixte finished the implementation of the new reorganize and split functionality in PDF, which will ship in Firefox 150! Users will be able to delete, copy, move pages, and to export a subset of pages to a new PDF.
Nicolò Ribaudo implemented the ability to open context menus on images in PDFs, allowing users to perform actions they are used to (such as downloading images). This was a long standing feature request (11 years!).

Firefox Translations

Evgeny Pavlov, Jaume Zaragoza-Bernabeu, and Sergio Ortiz Rojas contributed to training both new and improved Translations models for use in Firefox.
- Bosnian
- Croatian
- Norwegian Bokmål
- Serbian
- Thai
- Traditional Chinese
- Vietnamese
Erik Nordin fixed an issue where text contained within stand-alone SVG images was not being translated (Bug 2003545).
Erik Nordin reworked the Translations settings to be compatible with the upcoming about:settings redesign (Bug 2002127).
Erik Nordin helped design a system to control the enablement of AI Features within Firefox, and worked to make the entire Translations feature set have the capability to be turned off and back on within the same browsing session (Bug 2010922, Bug 2010993).
Erik Nordin reworked the about:translations page in order to get it ready for an official release with a URL-bar QuickAction entry point. (Bug 2004463, Bug 2016677, Bug 2015798, Bug 2016658, Bug 2016675, Bug 2016690, Bug 2019753, Bug 2020014, Bug 2020062, Bug2020067, Bug2022838, Bug 1814168, Bug 1814195, Bug 1841109, Bug 1869772, Bug 1879933, Bug 1970962, Bug 1990333, Bug 1991224, Bug 1992230, Bug 1992231, Bug 1992232, Bug 1992233, Bug 2000959, Bug 2004471, Bug 2004473, Bug 2019119, Bug 2019120, Bug 1970963, Bug 2004454, Bug 2010399, Bug 2023677, Bug 1836451, Bug 1999999, Bug 2004476, Bug 2004477, Bug 2004479, Bug 2004962, Bug 2007007, Bug 2007194, Bug 2007551, Bug 2008213, Bug 2008257, Bug 2010335, Bug 2019116, Bug 2019117, Bug 2019121, Bug 2019123, Bug 2020697, Bug 2020841, Bug 2024467)
- Thank you to Dasha Andriyenko for designing the visuals and UX of the page.
- Thank you to Kim Bryant for managing the product and release considerations.
- Thank you to Sam Foster and Greg Tatum who reviewed a significant portion of the code.
- Thank you to Ciprian Georgiu and Giorgia Nichita for testing quality assurance.
- Thank you to Anna Yeddi for reviewing engineering accessibility characteristics.
- Thank you to Dale Harvey for designing the QuickAction system that this feature plugs into.
Leonardo Paffi improved our testing capabilities by allowing us to serve inline HTML on the fly, rather than having to add an HTML file into the repository. This eases the burden of overhead to test special-case language characteristics, and ultimately helped us release Norwegian Bokmål (Bug 1996967).
Leonardo Paffi improved our handling of the macro language tag for Norwegian (no) to be compatible with our support for Norwegian Bokmål translations (Bug 2019123).
Tyler Etchart removed in-code references to quality estimation models, which are not utilized during translation inference within Firefox (Bug 1889753).
Tyler Etchart updated the generated Translations WASM JavaScript code to have explicit. comments expressing that the file is generated and should not be modified (Bug 1968038).
Tyler Etchart removed some old dead code related to prior ideas for Translations within Firefox (Bug 1996681).
Emilio Cobos Álvarez fixed an issue where the checkboxes within the Full-Page Translations Panel settings menu were no longer appearing (Bug 2010234).

Phabricator, moz-phab, and Lando

Connor Sheehan implemented ETL from Lando to STMO, which allows us to get better visibility into lando's performance and usage, e.g., the new uplift feature: Client Challenge
Zeid continues spear-heading the GitHub PR pilot, gathering feedback and fixing usability issues as they are reported. One key focus was on supporting triggering the Code Review Bot on request, via pushes to try.
Olivier Mehani added backward-compatible support for try pushes in the new instance of lando. It will become the default soon, but you can try it out now by setting LANDO_TRY_CONFIG=lando-prod-new in your environment prior to running `mach try .
Olivier Mehani landed a small change to lando, to make the current Tree Status visible on main landing pages (Bug 2025629). This, with the landing queue visible on the job details pages, should help get a better understanding of why jobs sometimes seem to take longer than expected to land.
moz-phab had several new releases:
- Suhaib Mujahid added the --ai flag and submit.ai_review commit option to request an AI review of patches at submission time.
- Johan Lorenzo added the --test-plan flag to enable submitting a test plan from the CLI, which is useful for working with AI agents
- See the release notes here:

Release Engineering and Release Management

Ben Hearsum added new tests to verify update integrity on mozilla-central.
Julien Cristau updated the docker images for many build and related tasks from Debian 12 to Debian 13
Relman streamlined the release process by removing the Nightly soft code freeze and adjusting the Beta schedule to reduce end-of-cycle friction, create more effective stabilization time, and simplify release candidate workflows.
We now ship to the Xiaomi Store.
Delivered mid-cycle ESR dot releases to address critical security fixes ahead of the standard cadence, improving responsiveness while coordinating across multiple ESR versions and release channels.
Andrew Halberstadt helped support and build out the Firefox Enterprise release pipeline.

Release Operations

Mark Cornmesser improved Windows hardware management, including self-configuration and self-deployment capabilities, automated BIOS management, and standardization of BIOS settings across performance testing environments to ensure consistency and reliability.

Other

Thanks to Bug #2013401 mozilla::Maybe<scalar_type> generates better and denser code, which led to a reduction of 300kB for libxul.so
Thanks to A new clang-tidy pass we've been able to automatically add std::move in location where it could improve performance (see Bug 2012658)

Thanks for reading and see you next quarter!

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