1978055 - Investigate why Firefox tests don't trigger changed preference warning for pdfjs.migrationVersion, but Thunderbird tests do

Status: RESOLVED DUPLICATE of bug 1949503

(Firefox :: PDF Viewer, defect)

Description

[Kai Engert [:KaiE:]]

After bug 1977567, some Thunderbird tests show this message at the end:
ERROR TEST-EXPECTED-FAIL | comm/mail/base/test/browser/browser_dummyRow.js | changed preference: pdfjs.migrationVersion

Florian helped us with initial debugging, and we know it's triggered by:
https://searchfox.org/comm-central/rev/60d68d5b1e4972c9e4327b16b7aed7b1858bbdde/mail/components/MailGlue.sys.mjs#560

Question is:

Why doesn't this happen for FF tests related to pdfs ?
(I don't see a FF test calling that function. For FF that call is made in browser/components/BrowserGlue.sys.mjs BG_observe for the same topic.)

Just a wild guess as a starting point for discussing.
In Firefox, maybe that init code is already reached during mochitest startup, and thus the test framework already sees that pref in the initial state?
While in Thunderbird, we have to explicitly initialize it, after the mochitest startup, so it's seen as a change?

Comment 1

[Florian Quèze [:florian]]

(In reply to Kai Engert [:KaiE:] from comment #0)

In Firefox, maybe that init code is already reached during mochitest startup, and thus the test framework already sees that pref in the initial state?

Good guess! It's triggered by https://searchfox.org/mozilla-central/rev/a9e77c69ed8a2b408bbe64553316c7849ec3d267/browser/components/BrowserGlue.sys.mjs#1173-1181 during browser startup.

Comment 2

[BugBot [:suhaib / :marco]]

The severity field is not set for this bug.
:calixte, could you have a look please?

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