User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:101.0) Gecko/20100101 Firefox/101.0

Steps to reproduce:

Open Firefox Browser

Actual results:

Firefox browser is set as my default browser. Each time I open the browser, I am presented with a pop up asking "Make Firefox your default browser". I mark the 'Don't show this message again' box, and click on 'Set as default browser'. This takes me to a Windows 'Default Apps' settings page, which shows that Firefox is my default browser. I am running Firefox 101.0 (64 bit) and Windows 10 Home, Version 21H2, build 19044.1706.

Expected results:

None of the above.

The Bugbug bot thinks this bug should belong to the 'Firefox::Shell Integration' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Just to make sure we are on the same page, is this the prompt that you are seeing?

Kirk,

Yes, that is the message. The message started appearing a week or so ago and would appear each time I opened Firefox. Today is the first day that the message did not appear when I started Firefox.

Steve

Ok, so there appears to be two things going on here. The first is that we don't check the result of the "Don't show this message again" checkbox unless the user clicks "Not now". That does sound like a bug to me.

The second problem is that we aren't properly detecting that Firefox is already the default browser. If you see this problem again, it would be helpful for us if you could run this line in the browser console so we could see what's going on:

ChromeUtils.import("resource:///modules/ShellService.jsm").ShellService.isDefaultBrowser(false)

To do this, you will need to enable code execution in the Browser Console by navigating to about:config and setting devtools.chrome.enabled to true. Then you can open the Browser Console either with the hotkey Control+Shift+J (Command+Shift+J on macOS), or via Hamburger Menu->More Tools->Browser Console. Executing the line above should either return true, false, or an error.

I'm going to go ahead and fix the first problem. If you ever encounter this problem again and get back to us with the above information, we can try to fix the second problem too.

Kirk,

Thank you.

Steve

Hmmm… I see back in 2012, shouldCheckDefaultBrowser was an unconditional setting or more accurately, it always assigned the value based on the checkbox:
https://searchfox.org/mozilla-central/rev/27a483110a010e92a4707d4c9b01d163c4b38c8e/browser/components/nsBrowserGlue.js#811-813

It switched to conditional assignment in 2014 with bug 1086958 and has maintained it that way ever since:
https://searchfox.org/mozilla-central/rev/a8c8dc10046dc96210f406e0c7da5ad95a20f8af/browser/components/nsBrowserGlue.js#2483-2485

Bug 1086958 comment 4 does highlight this behavior change, so it was intentional for fixing bug 1041516. So potentially the "first" problem from comment 4 is WONTFIX if we don't want to regress the original fix.

I would prefer that this bug be used specifically to track figuring out why Firefox sometimes doesn't properly recognize that it is already the default browser. While we wait to see if this problem reoccurs for the reporter so we can track it down, I am moving the other components of the problem to separate bugs:

• Bug 1774671 - Default Browser dialog's "Don't show this message again" checkbox lies to the user if dialog is accepted
• Bug 1774677 - Default Browser dialog is shown in an infinite loop if we fail to check that we are already the default browser
• Bug 1774680 - Default Browser dialog is shown if another Firefox installation is already the default browser

Comment on attachment 9280343 [details]
Bug 1772662 - Obey default browser prompt's "Don't show again" even if prompt is accepted r=Mardak

Revision D148698 was moved to bug 1774671. Setting attachment 9280343 [details] to obsolete.

It looks like this landed but the bug was not closed (unless it's open for other reasons)? https://hg.mozilla.org/mozilla-central/rev/b6ed2f1c7ece60d9e8b20dee38ca4b4d841d7e35

I split out dependent bugs to mitigate this situation, but my opinion is that the actual fix here would be fix the issue where Firefox doesn't recognize that it is already the default browser.

But since the problem stopped happening (according to Comment 3), it's quite like likely that we just aren't going to be able to get enough information to figure out what was going on here. So I'll go ahead and close this as INCOMPLETE. We can reopen it if the problem reoccurs.