1711218 - User overwritten "User" branch-type preferences are reset to their default values when unenrolling from experiments instead of their user-set values

Status: VERIFIED FIXED

(Firefox :: Normandy Client, defect)

Description

[Patriciu Pop [:ppop], Ecosystem QA]

Attachment: user-set-prefs-reset.gif

[Affected versions]:

• Firefox Nightly 90.0a1, Build ID 20210513214800

[Affected platforms]:

• Windows 10 x64
• macOS 10.15.7
• Linux Mint 20 x64

[Prerequisites]:

• Have a Normandy recipe for a multi-preference-experiment that uses the "User" branch type set up and published.
• Have a Firefox profile enrolled in the experiment.

[Steps to reproduce]:

1. Open the browser with the profile from prerequisites and navigate to the "about:config" page.
2. Search for the preference targeted by the experiment and change its value.
3. Navigate to the "about:studies" page and click the "Remove" button.
4. Return to the "about:config" page and observe the value of the targeted preference.

[Expected result]:

• The preference has the value set by the user.

[Actual result]:

• The preference value is reset to the Firefox default.

[Notes]:

• The issues is reproducible if the user changes the value of the pref using either the "about:config" page or the UI.
• Used the following Normandy Stage recipe to test: 1397.
• Attached a screen recording of the issue:

Comment 1

[Michael Cooper [:mythmon]]

Attachment: Bug 1711218 - Don't undo user pref changes when Normandy experiments end r=gijs

When a user chanes a preference involved in a Normandy experiment, we no longer
immediately end the experiment. This caused a problem because Normandy didn't
check for user changes when resetting prefereces at the end of an experiment.
As a result it would reset all preferences back to their original values on the
specified branch, even if that would mean changing a preference it knows the
user had modified.

This change causes Normandy to never reset the user branch of an experiment
preference that the user has changed. This is true even if the user changes the
preference away from the experimental value and then back to it.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/cd30ec1b16a3
Don't undo user pref changes when Normandy experiments end r=Gijs

Comment 3

[Narcis Beleuzu [:NarcisB]]

https://hg.mozilla.org/mozilla-central/rev/cd30ec1b16a3

Comment 4

[Patriciu Pop [:ppop], Ecosystem QA]

I have verified that this issue is no longer reproducible and user modified preferences remain set after unenrollment. Tested using Firefox Nightly 90.0a1, Build ID 20210525093431 on Windows 10 x64, macOS 10.15.7, and Ubuntu 20 x64.