2065302 - Remove the unused _discarded field in UrlbarParentController.sys.mjs

Status: RESOLVED FIXED

(Firefox :: Address Bar, task, P3)

Description

[Dão Gottwald [:dao]]

TelemetryEvent._discarded in browser/components/urlbar/UrlbarParentController.sys.mjs is written but never read, and should be removed.

There are exactly two references, both assignments:

• in record(), inside the finally block: this._discarded = false;
• in discard(): this._discarded = true;

Nothing reads the field, and it has no declaration either -- those two assignments are the only places it exists. Its last reader was removed in bug 1888905 (April 2024), which dropped the if (this._discarded && this._category && ...) check that used it.

The fix is to delete both assignment lines. Two things to leave alone: keep the if (this._startEventInfo) check that discard() wraps around its assignment, and don't touch _startEventInfo itself -- that one is very much in use. No other restructuring of either method is wanted.

Link to the code:
https://searchfox.org/firefox-main/source/browser/components/urlbar/UrlbarParentController.sys.mjs

Both references, which this search should stop returning once the patch is done:
https://searchfox.org/firefox-main/search?q=_discarded&path=browser%2Fcomponents%2Furlbar

To verify the fix:

./mach lint -l eslint browser/components/urlbar/UrlbarParentController.sys.mjs
./mach mochitest browser/components/urlbar/tests/browser-engagementTelemetry/

That mochitest directory is the engagement-telemetry suite, which exercises both record() and discard(). It should stay green: removing a field that nothing reads cannot change behavior.

Tutorial to contribute:
https://firefox-source-docs.mozilla.org/contributing/contribution_quickref.html
https://firefox-source-docs.mozilla.org/contributing/stack_quickref.html

Please don't ask for the bug to be assigned. It will be automatically assigned to the first patch.

Comment 1

[ianlewisuk1]

New contributor working on a patch for this bug

Comment 2

[Amadi]

Attachment: Bug 2065302 - Remove unused TelemetryEvent._discarded in UrlbarParentController.sys.mjs. r=#urlbar-reviewers

TelemetryEvent._discarded in browser/components/urlbar/UrlbarParentController.sys.mjs is written but never read

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/60ff83ebc15d
https://hg.mozilla.org/integration/autoland/rev/51928672ff32
Remove unused TelemetryEvent._discarded in UrlbarParentController.sys.mjs. r=urlbar-reviewers,dao

Comment 4

[Norisz Fay [:noriszfay]]

https://hg.mozilla.org/mozilla-central/rev/51928672ff32