[tbb-bugs] #33342 [Applications/Tor Browser]: Disconnect search addon causes error at startup

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#33342: Disconnect search addon causes error at startup
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 Reporter:  sysrqb                            |          Owner:  tbb-team
     Type:  defect                            |         Status:
                                              |  needs_information
 Priority:  Medium                            |      Milestone:
Component:  Applications/Tor Browser          |        Version:
 Severity:  Normal                            |     Resolution:
 Keywords:  TorBrowserTeam202003R, tbb-9.5a9  |  Actual Points:  0.5
Parent ID:                                    |         Points:
 Reviewer:  brade,mcs                         |        Sponsor:
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Comment (by acat):

 Sorry, I trusted my mail classification too much and missed mcs question.
 Replying to [comment:7 mcs]:
 > One question: would it also work to remove the `addonStartup.json.lz4`
 file? If I remember correctly it is a cache that would get rebuilt based
 on the installed addons.
 I think not, in the sense that it might break some stuff. For example, if
 you remove `addonStartup.json.lz4` the search builtin extensions will not
 load at all, which means that the search icons in the urlbar will be
 broken (similar to #31563). Launching the browser with env variable
 `RELOAD_ENGINES=1` makes `SearchService.jsm` reinstall these search
 extensions again, so perhaps removing `addonStartup.json.lz4` + forcing
 search extensions reinstall might do the trick.

 I'm not completely sure about the details, but I think one of the reasons
 why `addonStartup.json.lz4` is "not just a cache", at least for builtin
 extensions, is that the `BuiltInLocation` is not [https://searchfox.org
 /mozilla-
 esr68/rev/0ef234279fd0608a8fd6bb1f792d080087d638d8/toolkit/mozapps/extensions/internal/XPIProvider.jsm#979
 enumerable], which means that in [https://searchfox.org/mozilla-
 esr68/rev/0ef234279fd0608a8fd6bb1f792d080087d638d8/toolkit/mozapps/extensions/internal/XPIProvider.jsm#1455
 scanForChanges] the builtin location is skipped and it cannot notice the
 fact that the addon disappeared from `addonStartup.json.lz4` (because
 actually it was the only place this was persisted on). I think this would
 not be an issue if the search engines were temptatively installed every
 time, like  it's done with the [https://searchfox.org/mozilla-
 esr68/rev/0ef234279fd0608a8fd6bb1f792d080087d638d8/browser/components/BrowserGlue.jsm#1179
 themes], but that's not the case (probably to make the browser load
 faster?).

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/33342#comment:9>
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