The prefs shim should either merge in defaults at startup or it should write everything out. (But probably merging is best.) See https://bugzilla.mozilla.org/show_bug.cgi?id=1291049#c63

Thanks for filing Tom! (In reply to Tom Tromey :tromey from comment #0) > The prefs shim should either merge in defaults at startup or it > should write everything out. (But probably merging is best.) I agree, merging would be the best here. This way if a default value changes and has not been overridden by the user, the new default value will be used.

Wow, I really don't know what I was thinking in this code. The startup stuff all seems backward.

Comment on attachment 8801146 [details] Bug 1309384 - merge default and user prefs in Services shim; https://reviewboard.mozilla.org/r/85918/#review84586 Great patch, thanks for fixing this! Just two nits. (For the record I tested your patch with the inspector webpack bundle and it fixes the startup issue) ::: devtools/client/shared/shim/Services.js:363 (Diff revision 1) > * @param {Any} userValue the user value to use if the pref does not exist > * @param {Any} defaultValue the default value to use if the pref > * does not exist > * @param {Boolean} hasUserValue if a new pref is created, whether > * the default value is also a user value > + * @param {Boolean} init if true, then this call is initialization nit: The two previous arguments are swapped in the jsdoc, would be nice to fix it here. ::: devtools/client/shared/shim/test/test_service_prefs_defaults.html:67 (Diff revision 1) > + > + SimpleTest.finish(); > +} > + > +SimpleTest.waitForExplicitFinish(); > +do_tests(); nit: Since the test is synchronous I think you can get rid of SimpleTest.finish(), SimpleTest.waitForExplicitFinish() as well as the "do_tests" wrapper.

Tom: I pushed https://bugzilla.mozilla.org/attachment.cgi?id=8801183 here so that I don't forget. While testing your patch I realized the preferences where still not saved when reloading the inspector. Maybe it's best to address it in a separate bug? But if you want to integrate it and land it here, that works for me :)

Comment on attachment 8801183 [details] Bug 1309384 - fix override of default preference; https://reviewboard.mozilla.org/r/85926/#review84618 Thanks, this looks good.

Comment on attachment 8801227 [details] Bug 1309384 - fix override of default preference; https://reviewboard.mozilla.org/r/85940/#review84620 I already r+d the other one, this is just fixing it after the changes requested to the first patch.

Comment on attachment 8801183 [details] Bug 1309384 - fix override of default preference; I would have thought that mozreview would do this automatically.

Pushed by ttromey@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/d61c25d687c4 merge default and user prefs in Services shim; r=jdescottes https://hg.mozilla.org/integration/autoland/rev/ce7b9aa047e8 fix override of default preference;r=tromey

https://hg.mozilla.org/mozilla-central/rev/d61c25d687c4 https://hg.mozilla.org/mozilla-central/rev/ce7b9aa047e8