The Joy of Coding

Reminder - no plan survives breakfast.

Episode guide

• Feel free to send pull requests to the repo!
• Here’s a contributing guide!
• Here’s the guide for creating pull requests that smurfd used and recommends!

Today

• Q:
  "missed the submission window, so here is my question again:
  There was a regression on 10th April 2026 breaking the functionality of middle clicking the "Go to the address in Location Bar" arrow button to open the address in a new tab.
  
  however the bug mozregession provides is not public, and it's title does not make sense related to the regression:
  
  2026-04-14T18:40:43.437000: INFO : Narrowed integration regression window from [aee77767, 602084a8] (4 builds) to [e41f1f9a, 602084a8] (2 builds) (~1 steps left)
  2026-04-14T18:40:43.473000: DEBUG : Starting merge handling...
  2026-04-14T18:40:43.476000: DEBUG : Using url: https://hg.mozilla.org/integration/autoland/json-pushes?changeset=602084a80545c3aa2879ec54585f298966b00839&full=1
  2026-04-14T18:40:43.480000: DEBUG : redo: attempt 1/3
  2026-04-14T18:40:43.482000: DEBUG : redo: retry: calling _default_get with args: ('https://hg.mozilla.org/integration/autoland/json-pushes?changeset=602084a80545c3aa2879ec54585f298966b00839&full=1',), kwargs: {}, attempt #1
  2026-04-14T18:40:43.488000: DEBUG : urllib3.connectionpool: Resetting dropped connection: hg.mozilla.org
  2026-04-14T18:40:44.270000: DEBUG : urllib3.connectionpool: https://hg.mozilla.org:443 "GET /integration/autoland/json-pushes?changeset=602084a80545c3aa2879ec54585f298966b00839&full=1 HTTP/1.1" 302 0
  2026-04-14T18:40:45.446000: DEBUG : urllib3.connectionpool: https://hg-edge.mozilla.org:443 "GET /integration/autoland/json-pushes?changeset=602084a80545c3aa2879ec54585f298966b00839&full=1 HTTP/1.1" 200 None
  2026-04-14T18:40:45.482000: DEBUG : Found commit message:
  Revert "Bug 2029066 - Remove Sinking of Live instructions. r=iain" for causing spidermonkey build bustages at Sink.cpp
  
  This reverts commit dcb553336bdbc8a96073e287127b82eb5144d8aa.
  
  2026-04-14T18:40:45.488000: DEBUG : Did not find a branch, checking all integration branches
  2026-04-14T18:40:45.492000: INFO : The bisection is done.
  2026-04-14T18:40:45.496000: INFO : Stopped
  
  there is a similar "Bug 2033231 - Middle clicking alternate engines no longer perform a search on the current search bar text in a new tab" but the dates don't match and the issue isn't fixed in current Nightly.
  
  I assume this regression isn't an intended change but I can't tell without seeing the regressor bug.
  I used the functionality as a workaround for what has caused internal Mozilla debate: 724239, 776167, 1415136
  and there is still inconsistent behaviour between about:newtab, about:blank and about:privatebrowsing"

  • This bug: https://bugzilla.mozilla.org/show_bug.cgi?id=2037361, which is assigned (as of this writing, an hour ago!)

• Query for finding regressionwindow-wanted bugs

  • ./mach mozregression to find the regressor
• Let's solve a mystery!
  
  • Where are those spans going? Where is the progress going?!
    • Our self-closing tags were confusing things. Got rid of them!
  • Build fluent migration for the strings we moved
    • Still to do
  • Fix button styling to match existing button behaviour
    • Done
• TODO:
  • Talk to emilio about center cropping support in CSS for privileged markup / layout
  • Factor out download item UI into a reusable Lit element

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Chat

• Join us in the Livehacking room on Mozilla’s Matrix instance! Here’s documentation on how to join. I’m only sorta monitoring the Twitch chat. A bot will try to bridge Matrix and Twitch (joc-bridgebot).

Links

• Nathan Baggs
• Felicia Bacon
• nbp hacks on the SpiderMonkey JS engine
• Alessandro Castellani has been streaming himself livehacking on Thunderbird
• emilio hacks on Firefox!
• Compiler Compiler - watch a Mozilla engineer hack on the SpiderMonkey JavaScript engine!
• Andreas Kling hacks on a custom browser engine for a hand-rolled OS called SerenityOS
• The Joy of Coding: Community-Run Episode guide
  • Feel free to send pull requests to the repo!
  • Here’s the guide for creating pull requests that smurfd used and recommends!
• I've been mirroring the episodes to YouTube
• Code Therapy with Danny O’Brien
• Watch a developer put together a Windows game from scratch (no third-part engines) - really great explanations: https://handmadehero.org/
• /r/WatchPeopleCode for more livehacking!

Glossary

• BHR - “Background Hang Reporter”, a thing that records information about when Firefox performs poorly and sends it over Telemetry
• e10s ("ee ten ESS") - short for Electrolysis, which is the multi-process Firefox project
• CPOW ("ka-POW" or sometimes "SEE-pow") = Cross-Process Object Wrapper. See this blog post.
• Deserialize - "turn a serialized object back into the complex object”
• Serialize - "turn a complex object into something that can be represented as primitives, like strings, integers, etc
• Regression - something that made behaviour worse rather than better. Regress means to “go backward”, more or less.
• l10n - localization
• a11y - accessibility
• i18n - internationalization
• k8s - kubernetes

Feedback

• https://fosstodon.org/@mconley/ on Mastodon
• You can chat with me on Matrix at @mconley:mozilla.org
• mikeconley.ca/blog
• mconley at mozilla dot com