Nyquist plug-ins cannot be installed without restarting Audacity

[SteveDaulton]

Describe the bug
Nyquist plug-ins cannot be installed without restarting Audacity. This is a usability regression against previous versions of Audacity that allowed a plug-in to be installed, enabled, and used immediately without having to save the current project and restart Audacity.

To Reproduce
Steps to reproduce the behavior:

1. Install a Nyquist plug-in with the Nyquist Plug-in Installer

Actual behavior
The plug-in is not enabled, and cannot be enabled until Audacity is closed and restarted.

Expected behavior
The plug-in to be enabled, or at least available for enabling.

Screenshots
If applicable, add screenshots/video to help explain your problem.

Additional information (please complete the following information):

• OS: [e.g. Mac High Sierra, Ubuntu 18.04, Windows 10] Xubuntu 20.04
• Version [e.g. Audacity 2.5.1] 3.2.0 6a5645

Additional context
Add any other context about the problem here.

• Adding additional context from Nyquist Plug-in Installer #2966 to combine these two issues and avoid redundancy.

Note that this would also include Nyquist plugins after being installed via the Nyquist Plugin installer so this should be confirmed as well when tested later. So specifically from #2966 this should be confirmed as part of the fix for this item:

"After installing a new Nyquist Plug-in, the Nyquist Plug-in installer says: Use the Plugin Manager to enable effects but when you do so, the plugin does not appear in the plugin manager without closing and relaunching Audacity."

[petersampsonaudacity]

This appears to be more general, testing on W10 with latest 3.2.0 master

1. I keep my Queen Mary Vamp plug-ins hidden from Audacity by renaming C:\Program Files\Vamp Plugins to C:\Program Files\X-Vamp Plugins
2. launch Audacity 3.2.0
3. Observe: no sign of the Vamp plug-ins in Audacity's Plugin Manager
4. rename C:\Program Files\X-Vamp Plugins to C:\Program Files\Vamp Plugins
5. Plug-in Manager
6. Observe> still no sign of the Vamp plug-ins in Audacity's Plugin Manager
7. Exit Audacity
8. launch Audacity 3.2.0
9. Observe: the Vamp plug-ins are now loaded and are shown in the Analyze menu - and can be seen in Plug-in Manager.

So I suspect that this applies to all plug-ins that are added to a user's environment while Audacity is open/running. So maybe we need a new command (or a button in the dialog of the Plug-in Manager) that does the plug-in scanning that now only gets invoked at launch time.

[Paul-Licameli]

Does this problem bisect (coarsely) to @vsverchinsky 's work in commits 465d3ee...f099a2e ?

[Paul-Licameli]

Or the earlier work in 04e8f11...12db358 ?

[petersampsonaudacity]

@Paul-Licameli I can't figure out which builds those two are ...

[Ryan-Miller-Audacity]

Note that this problem is still occurring in the latest master build of 3.2 as described. I couldn't narrow it don't to a specific commit that Paul mentioned earlier (04e8f11...12db358) because the artifacts for those runs are expired; however, I was able to check it witihin commits 465d3ee...f099a2e (it's actually the very first build that I ever pulled on my first day 😆 ) and it does occur within that group of changes.

[petersampsonaudacity]

@SteveDaulton Can this issue be resolved with the new Rescan button in the Plugin Manager?

https://alphamanual.audacityteam.org/man/Manage_Effects,_Generators_and_Analyzers

[SteveDaulton]

@SteveDaulton Can this issue be resolved with the new Rescan button in the Plugin Manager?

Testing with the latest build from the master branch, there isn't a "Rescan" button.

[LWinterberg]

the most up-to-date branch is the alpha-3.2.0 branch

[SteveDaulton]

Testing with the alpha-3.2.0 branch, the "Rescan" button does not only rescan for plug-ins, it also automatically enables every plug-in that it finds on my computer, thus re-enabling the hundreds of plug-ins that I've previously spent time disabling.

Not only that, but after pressing "Rescan", when I see that it wants to enable hundreds of plug-ins that I don't want enabled, it then fails to honour the "Cancel" button:

1. Ensure that you have some custom effects installed on your computer.
2. Launch Audacity
3. Disable all custom effects
4. Close and restart Audacity
5. Check and see that you have only the standard set of plug-ins.
6. Launch "Manage Plugins"
7. Click the "Rescan" button
8. (optional) Curse
9. Press the "Cancel" button
10. Observe that the custom effects are NOT listed in the menus
11. Quit Audacity and relaunch
12. Observe that the custom effects ARE now listed in the menus.

Now I have to go through the effects again and disable all of those that I disabled previously.
I seriously hope that this is a bug and not the intended behaviour.