Code coverage data is now exclusively in Searchfox

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Marco Castelluccio

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Mar 3, 2026, 6:28:55 AMMar 3
to dev-platform, Firefox Dev
Hello,
The https://coverage.moz.tools/ service has been retired and will
disappear shortly.

Coverage data is now only available in Searchfox, both at the directory
level (example
https://searchfox.org/firefox-main/rev/0fce12de99c5e7d74536d8f93cf9778ce6199a1f/,
coverage percentages in the "Coverage" column) and at the file level
(example
https://searchfox.org/firefox-main/rev/0fce12de99c5e7d74536d8f93cf9778ce6199a1f/browser/base/content/browser.js,
coverage data in the coverage strip on the left).

If you are browsing a file on Searchfox and coverage data is not
available, when you hover the coverage strip there is a link "Show
previous file revision with coverage".

Thanks!
- Marco.

Tom Ritter

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Mar 3, 2026, 6:34:58 AMMar 3
to Marco Castelluccio, dev-platform, Firefox Dev
Thank you for the steady improvement in our tooling.  Can I ask - what does  "There was coverage data for this file but not for this line." mean?  


-tom

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Nicolas Qiu Guichard

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Mar 3, 2026, 6:45:15 AMMar 3
to Tom Ritter, Marco Castelluccio, dev-platform, Firefox Dev
Hi,

Le mardi 3 mars 2026, 12:34:40 heure normale d’Europe centrale 'Tom Ritter' via dev-pl...@mozilla.org a écrit :
> Thank you for the steady improvement in our tooling. Can I ask - what
> does "There was coverage data for this file but not for this line." mean?
>
> Example:
> https://searchfox.org/firefox-main/rev/0fce12de99c5e7d74536d8f93cf9778ce6199a1f/ipc/mscom/AgileReference.cpp

The last few lines of every files display that because instead of outputing -1
for “not instrumented”, grcov stops at the last instrumented line.

In your case though, you're also missing coverage data because of
https://bugzilla.mozilla.org/show_bug.cgi?id=2002904 which is being
fixed (not really related to Searchfox, this also bit coverage.moz.tools).

Cheers,
--
Nicolas Qiu Guichard | nicolas....@kdab.com | Software Engineer
KDAB (France) S.A.S., a KDAB Group company
Tel: France +33 (0)4 90 84 08 53, http://www.kdab.fr
KDAB - Trusted Software Excellence

Tom Schuster

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Mar 5, 2026, 7:05:01 AMMar 5
to Marco Castelluccio, dev-platform, Firefox Dev
Hi!

This is very exciting. Thank you and Nicolas for working on this. When can we expect the data on searchfox to become available? I can't find "Show
previous file revision with coverage" in the UI. Is there an API for getting the coverage data?

Thanks
Tom

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Nicolas Qiu Guichard

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Mar 11, 2026, 5:31:47 PMMar 11
to Tom Schuster, Marco Castelluccio, dev-platform
Hi Tom,

Le jeudi 5 mars 2026, 13:04:46 heure normale d’Europe centrale 'Tom Schuster'
via dev-pl...@mozilla.org a écrit :
> This is very exciting. Thank you and Nicolas for working on this. When can
> we expect the data on searchfox to become available? I can't find "Show
> previous file revision with coverage" in the UI.

You've hit https://bugzilla.mozilla.org/show_bug.cgi?id=2021300 which
temporarily prevented Searchfox from displaying coverage.

The data is back, with a week worth of coverage history now. You can navigate
between revisions using the links in the coverage popup while I'm working on
importing more history and bringing back the timeline we had above the folder
view on coverage.moz.tools.

> Is there an API for getting the coverage data?

There's no Searchfox API for that (yet), but you can get the raw coverage data
from the Google Cloud bucket gs://relman-code-coverage-prod/mozilla-central.

Frederik Braun

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Mar 13, 2026, 6:00:12 AMMar 13
to Nicolas Qiu Guichard, Tom Schuster, Marco Castelluccio, dev-platform
Hi all,

It's great to see progress on code coverage, as it is instrumental ground truth data to our analysis efforts.
It seems to me that the last commit on main is almost all of the time "no coverage data yet" - are there timing issue?

Also, looking at previous commits that have coverage info, I prefer percentages over absolute values.
The text description reads: "This line was hit 18 times per coverage instrumentation." - that seems much harder to evaluate than a percentage, no?


Does that match discussions and use cases other teams have?
Would you rather we file a bug instead of continuing the discussion here?


Thanks!
Freddy


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Nicolas Qiu Guichard

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Mar 23, 2026, 10:18:55 AM (12 days ago) Mar 23
to Frederik Braun, Tom Schuster, Marco Castelluccio, dev-platform
Hi Frederik and all,

Le vendredi 13 mars 2026, 10:59:57 heure normale d’Europe centrale Frederik
Braun a écrit :
> It seems to me that the last commit on main is almost all of the time "no
> coverage data yet" - are there timing issue?

Yes, currently the Searchfox indexer run isn't really synced with the
availability of coverage data. Historically the availability of coverage data
has also been flaky and could lag behind by a few days. This is being improved.

> Also, looking at previous commits that have coverage info, I prefer
> percentages over absolute values.
> The text description reads: "This line was hit 18 times per coverage
> instrumentation." - that seems much harder to evaluate than a percentage,
> no?

What percentage do you have in mind? Or rather a percentage of what?

We display a percentage of how many lines have at least 1 hit over the total
number of lines that were instrumented in the directory view, and we will
soon display that same percentage in the header of the file view,:this is
coming back with the coverage history graph in bug 2002218.

But for each line I don't think there's a sensible total to compare the hit
count to.

> Would you rather we file a bug instead of continuing the discussion here?

There's a meta-bug at https://bugzilla.mozilla.org/show_bug.cgi?id=2002215, so
yes please attach feedback there.
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