STR:

1. open Firefox on a clean profile
2. open the options/prefs, search for PDF. Check it defaults to "Open with Firefox"
3. open a content-disposition attachment pdf, e.g. https://www.seattlesymphony.org/~/media/files/notes/schubert-sonata-21-b-flat.pdf
4. pick anything other than "open in nightly/Firefox". Do not tick "do not ask me again"
5. reload the options, search for PDF again

ER:
it should stay "open with firefox"

AR:
it becomes "always ask"

This is bad, because then even inline PDFs don't get displayed inline anymore.

Pretty sure this is a regression.

These steps regressed a week ago on Nightly, from bug 1653117.

The reports in bug 1655974 about defaults becoming "always ask" are from ESR or release, and so I'm worried there's some other STR that I'm missing here.

Jared, do you have cycles to help investigate?

Set release status flags based on info from the regressing bug 1653117

I might have cycles today/Monday, but there are a few others bugs that I'm trying to chase down while also getting more things in for 81. If you have some time that would be great but I know you're super busy too.

(intentionally cleared and re-set needinfo so you would get mail that I responded)

Hi Gijs, can you please (let) triage this?

I moved the investigation into bug 1661432. Here, let's "just" fix the regression.

https://hg.mozilla.org/mozilla-central/rev/605317e5db8a

Comment on attachment 9172819 [details]
Bug 1660277 - adjust when we save per-filetype download preferences in the helper app dialog for types handled internally, r?jaws

Beta/Release Uplift Approval Request

• User impact if declined: People have terrible PDF experiences
• Is this code covered by automated tests?: Yes
• Has the fix been verified in Nightly?: No
• Needs manual test from QE?: Yes
• If yes, steps to reproduce: See comment #0
• List of other uplifts needed: n/a
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): Relatively small change in this #$&^$*2$# dialog. Comes with more automated tests.
• String changes made/needed: None

Comment on attachment 9172819 [details]
Bug 1660277 - adjust when we save per-filetype download preferences in the helper app dialog for types handled internally, r?jaws

Ouch. Approved for 81.0b5.

Comment on attachment 9172819 [details]
Bug 1660277 - adjust when we save per-filetype download preferences in the helper app dialog for types handled internally, r?jaws

Actually, this needs a rebased patch (Beta doesn't know what IOUtils is)

Comment on attachment 9172819 [details]
Bug 1660277 - adjust when we save per-filetype download preferences in the helper app dialog for types handled internally, r?jaws

We figured it out. This needs bug 1660015 to make ESLint happy. Re-approving!

https://hg.mozilla.org/releases/mozilla-beta/rev/60e3cf505151

Reproduced the initial issue reported here using an old Nightly (2020-08-20), verified that this is fixed using Firefox 81.0b7 and Latest Nightly 82.0a1 across platforms (Windows 10 64bit, macOS 10.15, Ubuntu 18.04 64bit).

Brendan, can you think of any reasonable way we can restore settings for beta/nightly users without clobbering them for people who have deliberately changed them? I assume not, but I figured I'd ask...

Unfortunately, I don't see another way. I looked around a bit hoping there was some way that the mime type handler settings were changed in a way we could detect when the bug was present, but I'm not seeing anything.