Bug: C-C TB "Rejected attempt to change type of pref" warnings
Status: RESOLVED
Priority: --
Resolution: FIXED
Created: 2022-09-05 23:04:14+00:00
Resolved: 2022-09-07 06:55:41+00:00

I am creating local patches and build and test FULL DEBUG version of
C-C TB under linux.

I found the following warnings in local TB mochitest log.
I think they suggest incorrect pref value settings.
The test harness seems to set incorrect pref values before invoking tests.
```
56: Main Thread] WARNING: Rejected attempt to change type of pref extensions.formautofill.creditCards.available's user value from bool to string: file /NEW-SSD/NREF-COMM-CENTRAL/mozilla/modules/libpref/Preferences.cpp:1758

1: Main Thread] WARNING: Rejected attempt to change type of pref mail.provider.enabled's user value from bool to string: file /NEW-SSD/NREF-COMM-CENTRAL/mozilla/modules/libpref/Preferences.cpp:1758
```

The first warning appears 56 times while the second one appears once
during mochitest test suite run.


We can find the same warnings in other people's tryserver run as well.
For example, see the following job of Geoff's.
https://treeherder.mozilla.org/jobs?repo=try-comm-central&selectedTaskRun=VvpqC7JTRG6r2FEFDfJ_dg.0&revision=f81fb02e91f1b701693102ae185ead269b3390ec

The warnings for |extensions.formautofill.creditCards.available| are
almost in every live.log bct1, bct2, bct3, etc.

|mail.provider.enabled| warnings  is found in bct7 log.
https://firefoxci.taskcluster-artifacts.net/VvpqC7JTRG6r2FEFDfJ_dg/0/public/logs/live_backing.log

The following is an excerpt from the output of the following command executed locally on
the mochitest log.
egrep "(TEST_START|TEST_END|Rejected attempt)" log1484-mochitest.txt &
This is to show where the warning for |mail.provider.enabled| appears.
```
        ... [omitted] ...
933:33.82 TEST_START: comm/mail/test/browser/session-store/browser_sessionStore.js
933:53.03 TEST_END: Test OK. Subtests passed 2/8. Unexpected 0
934:02.26 GECKO(505756) [Parent 505756, Main Thread] WARNING: Rejected attempt to change type of pref extensions.formautofill.creditCards.available's user value from bool to string: file /NEW-SSD/NREF-COMM-CENTRAL/mozilla/modules/libpref/Preferences.cpp:1758
934:08.14 TEST_START: comm/mail/test/browser/smime/browser_multipartAlternative.js
934:12.13 TEST_END: Test OK. Subtests passed 1/1. Unexpected 0
934:25.74 GECKO(506010) [Parent 506010, Main Thread] WARNING: Rejected attempt to change type of pref extensions.formautofill.creditCards.available's user value from bool to string: file /NEW-SSD/NREF-COMM-CENTRAL/mozilla/modules/libpref/Preferences.cpp:1758
934:25.74 GECKO(506010) [Parent 506010, Main Thread] WARNING: Rejected attempt to change type of pref mail.provider.enabled's user value from bool to string: file /NEW-SSD/NREF-COMM-CENTRAL/mozilla/modules/libpref/Preferences.cpp:1758
934:31.63 TEST_START: comm/mail/test/browser/startup-firstrun/browser_menubarCollapsed.js
934:32.17 TEST_END: Test OK. Subtests passed 1/1. Unexpected 0
934:41.52 GECKO(506237) [Parent 506237, Main Thread] WARNING: Rejected attempt to change type of pref extensions.formautofill.creditCards.available's user value from bool to string: file /NEW-SSD/NREF-COMM-CENTRAL/mozilla/modules/libpref/Preferences.cpp:1758
934:47.32 TEST_START: comm/mail/test/browser/subscribe/browser_newsFilter.js
934:49.12 TEST_END: Test OK. Subtests passed 1/1. Unexpected 0
```