[tbb-bugs] #22618 [Applications/Tor Browser]: Downloading pdf file via file:/// is stalling if the external helper dialog is enabled

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#22618: Downloading pdf file via file:/// is stalling if the external helper dialog
is enabled
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 Reporter:  gk                                   |          Owner:  tbb-
                                                 |  team
     Type:  defect                               |         Status:
                                                 |  needs_review
 Priority:  Medium                               |      Milestone:
Component:  Applications/Tor Browser             |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  tbb-7.0-issues, tbb-regression,      |  Actual Points:
  tbb-e10s, TorBrowserTeam201708R                |
Parent ID:                                       |         Points:
 Reviewer:                                       |        Sponsor:
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Comment (by gk):

 Replying to [comment:10 mcs]:
 > Replying to [comment:9 arthuredelstein]:
 > > One question I have: it looks as though files are downloaded while the
 first dialog is displayed. That doesn't necessarily seem to be a problem,
 but are there temporary files where the file is being stored?
 >
 > Yes. Temporary files (.part) are created during the download and they
 are placed in the configured downloads directory. See the
 nsExternalAppHandler::SetUpTempFile() function here:
 https://dxr.mozilla.org/mozilla-
 esr52/source/uriloader/exthandler/nsExternalHelperAppService.cpp#1400
 >
 > We talked about this a little at one of our Monday meetings and Kathy
 and I had the impression that it was okay for the download to proceed as
 long as everything gets cleaned up if the user aborts the download. The
 difference in behavior between Tor Browser 6.5 and 7.x with this patch is
 that in 6.5 the Tor download warning prompt effectively paused the
 download because a modal dialog was presented.

 I think that's okay. We could think about a more complicated solution
 which involves not downloading to disk in PBM but it's fine having it in a
 different bug.

 I am still testing the patch and I have some review notes containing
 things I'd like to see changed/fixed. I'll post those once I am properly
 done. However, the patch seems to be important enough to get tested in an
 alpha as it solves a bunch of annoying regressions. That's why I included
 it for 7.5a4 even though not all parts of my review process are done yet.
 FWIW: mcs/brade: Thanks for this great work! It looks mostly good to me.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/22618#comment:11>
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