1767967 - Firefox UserChoice/set to default (in particular, for PDF) does not support at least Windows 1703 and 1803

Status: NEW

(Firefox :: Installer, defect, P3)

Description

[Cosmin Muntean [:cmuntean], Ecosystem QA]

Attachment: PDF handler.mp4

[Affected versions]:

• Firefox 100.0 Release, (Build ID - 20220428192727)

[Affected Platforms]:

• Windows 10 1803
• Windows 10 1703

[Prerequisites]:

• Have Firefox 100 Release installed.
• Make sure that Firefox is NOT set as the default browser.
• Have a new Firefox profile created, but never opened.
• Have the “user.js” (specific to the Enabled branch) pasted in the created profile.
• Have a PDF file downloaded on your computer.

[Steps to reproduce]:

1. Open the Firefox browser with the profile from prerequisites.
2. From the "about:welcome" page, click the "Set Firefox as default" button.
3. Restart the browser.
4. Navigate to the "about:telemetry#keyed-scalars-tab" page and search for the "os.environment.is_default_handler" keywords.
5. Observe the value of the "os.environment.is_default_handler" scalar.
6. Open a PDF file downloaded on your computer.

[Expected result]:
Step 5: The "os.environment.is_default_handler" scalar has the value "true".
Step 6: The PDF file is opened using Firefox.

[Actual result]:
Step 5: The "os.environment.is_default_handler" scalar has the value "false".
Step 6: The PDF file is NOT opened with Firefox.

[Notes]:

• We also managed to create a new VM for Windows 10 version 1703 OS build 15063, and the issue is also reproducible on this version.
• The issue is reproducible with both the experiment and the rollout.
• The issue is NOT reproducible on Windows 10 version 21H1, OS build 19043.1645 and Windows 11 version 21H2 (OS build 22000.613).
• Unfortunately, we are not sure if there are any other Windows versions where the issue is reproducible.
• Attached is a screen recording of the issue.

Comment 1

[Nick Alexander :nalexander [he/him] (PTO Feb 24-March 3)]

Sadly, this is a pre-existing issue with UserChoice. We'll target the experiment at 1809+.

Comment 2

[Nick Alexander :nalexander [he/him] (PTO Feb 24-March 3)]

We'll want to address this, if we can, as we onboard existing Firefox users to having set-to-default include PDF handling.

Comment 3

[Nick Alexander :nalexander [he/him] (PTO Feb 24-March 3)]

Cosmin: do you remember if "Set to default" made Firefox the default browser successfully on these versions? I.e., it failed to set Firefox as the default PDF handler but succeeded for the browser?

Comment 4

[Cosmin Muntean [:cmuntean], Ecosystem QA]

Hi Nick!

Yes, the Firefox browser is successfully set as the default browser, but it failed to set Firefox as the default PDF handler.

I have tested this with the option from "about:welcome" page, from "about:preferences" and also from the "Set Firefox as default" pop-up. For all of these cases, Firefox is successfully set as the default browser but it is not set as the default PDF handler.

Comment 5

[Nick Alexander :nalexander [he/him] (PTO Feb 24-March 3)]

I expect that Windows made UserChoice protect the .pdf protocol later than the browsing protocols (https, etc). This might simply set both registry entries (all of the time), or it might be that we gate on the Windows build ID to control the behaviour.