Why switch_session() doesn't work?

[Andrew15-5]

I created the basic plugin:

use zellij_tile::prelude::*;
use std::collections::BTreeMap;

#[derive(Default)]
struct State {}

register_plugin!(State);

impl ZellijPlugin for State {
    fn load(&mut self, _configuration: BTreeMap<String, String>) {
        switch_session(Some("existing-session"));
        close_self();
    }
    fn update(&mut self, _event: Event) -> bool {
        false
    }
    fn render(&mut self, _rows: usize, _cols: usize) {}
}

But it doesn't actually switch to the existing session — it only closes itself. I tried putting it into the other two callbacks, but it didn't change anything. I'm trying to achieve what is described in #2448 (reply in thread). zj a session-name doesn't work anymore because I now already start the shell inside the zellij. I need to remove the nestingness. I need an instant non-interactive result just like zj a <session>. How can I achieve this?

My only current "solution" is to start a new terminal with the desired zellij session (using an alias). The other "solution" would be to not run shell from the zellij by default, but that partially defeats the purpose of the multiplexer.

[cristiand391]

the switch_session command requires the ChangeApplicationState permission:
https://zellij.dev/documentation/plugin-api-commands#switch_session
https://zellij.dev/documentation/plugin-api-permissions

you need to request it in the load function like this:
https://github.com/cristiand391/zj-status-bar/blob/5048c3c841d47b2d35def393bf0f5676ed68e42d/src/main.rs#L37

[Andrew15-5]

Why in the default session manager plugin which uses this function there is no request of this permission?

zellij/default-plugins/session-manager/src/main.rs

Lines 54 to 68 in 56baf0b

	fn load(&mut self, configuration: BTreeMap<String, String>) {
	self.is_welcome_screen = configuration
	.get("welcome_screen")
	.map(|v| v == "true")
	.unwrap_or(false);
	if self.is_welcome_screen {
	self.active_screen = ActiveScreen::NewSession;
	}
	subscribe(&[
	EventType::ModeUpdate,
	EventType::SessionUpdate,
	EventType::Key,
	EventType::RunCommandResult,
	]);
	}

After running the snippet from above (zellij plugin -fs -- file:target/wasm32-wasi/debug/rust-plugin-example.wasm) it compiles the plugin, and then it closes due to close_self();. Or does nothing if only switch_session() is called. The addition of the request_permission(&[PermissionType::ChangeApplicationState]); changes nothing.

    fn load(&mut self, _configuration: BTreeMap<String, String>) {
        request_permission(&[PermissionType::ChangeApplicationState]);
        switch_session(Some("existing-session"));
        close_self();
    }

Also, at some point, the command that starts the plugin can and did stop working by just running indefinitely without any output. So the development session is now only for writing code and a different session is for running the plugin. Probably some kind of bug that kills the plugin starting ability in the current session.

[cristiand391]

Why in the default session manager plugin which uses this function there is no request of this permission?

interesting, haven't checked yet but maybe there's some internal logic that grant built-in plugins all required perms.

The addition of the request_permission(&[PermissionType::ChangeApplicationState]); changes nothing.

On the first load it should prompt you to confirm access to the requested permissions, did you see that screen?
What I usually do is to nuke zellij's cache and reload the plugin.

Also keep in mind that plugin commands don't block until they are done:
#2558

it could be that close_self ends up running before switch_session is done 🤷🏼

kinda related:
yesterday I wrote this plugin that uses the kill_sessions command:
#467 (comment)

something I noticed is that the UI wasn't printing the session name until ~1s after being rendered (which I get from the SessionUpdate event), so I had to make it wait until it gets it like this:
https://github.com/cristiand391/zj-quit/blob/c98e0741bd45d7c1de105e0055d5e0e504e76c65/src/main.rs#L43

you could try copying the logic from there to ensure switch_session only runs when the session info is available.

[Andrew15-5]

On the first load it should prompt you to confirm access to the requested permissions, did you see that screen?

Yes, a few times.

What I usually do is to nuke zellij's cache and reload the plugin.

How do you nuke tho cache? My only guess is that somehow I didn't grant the permission, and it just don't work now.

it could be that close_self ends up running before switch_session is done

Damn, that's rough...

Can I use those functions in any of the 3 callbacks, or only in the load/update?

you could try copying the logic from there to ensure switch_session only runs when the session info is available.

But why do I have to wait if I just need to switch to another session? Or I can't until that info is available? If that's true, I think the switch wouldn't be instant... :/

[cristiand391]

How do you nuke tho cache? My only guess is that somehow I didn't grant the permission, and it just don't work now.

on linux I run rm -rf $HOME/.cache/zellij. I think on macos is somewhere in ~/Library/Cache/zellij, I can confirm tomorrow.

Can I use those functions in any of the 3 callbacks, or only in the load/update?

I'm pretty sure in any of the 4 lifecycle methods (4th is the pipe one, documented in other section):
https://zellij.dev/documentation/plugin-lifecycle

But why do I have to wait if I just need to switch to another session? Or I can't until that info is available? If that's true, I think the switch wouldn't be instant... :/

Actually I don't think you would need to wait for switch_session.
I ran your example above but without calilng close_self, and after giving perms I see this line in the log:

ERROR  |zellij_server::plugins::z| 2024-05-28 22:27:52.365 [async-std/runti] [zellij-server/src/plugins/zellij_exports.rs:273]: Plugin '/home/cristiand391/code/gh/zj-switch-session-test/target/wasm32-wasi/debug/rust-plugin-example.wasm (ID 4)' permission 'ChangeApplicationState' denied - Command 'SwitchSession' denied 

that reminded me of the PermissionRequestResult event doc'd here:
https://zellij.dev/documentation/plugin-lifecycle.html#update

basically the plugin was calling switch_session before it actually requested the perms because request_permission didn't finish yet!

following the linked blog I was able to make this work by only running switch_session when it's confirmed the permission was granted:

Screencast.from.05-28-2024.11.06.23.PM.webm

here's the code:
https://gist.github.com/cristiand391/3a40974034b2731ca5e866850ec599d1

[Andrew15-5]

on linux I run rm -rf $HOME/.cache/zellij. I think on macos is somewhere in ~/Library/Cache/zellij, I can confirm tomorrow.

Oh, so the normal way. Ok. (Linux FTW!)

I don't see any documentation of the PermissionType::ReadApplicationState that is needed for EventType::PermissionRequestResult, but looks like it's necessary...

Ok, so, I finally was able to do the plugin. But there are still 2 issues: I can't hide it because it needs permission the first time and sometimes when I launch it, it will still take about 0.5 or 1 second. But in some cases the switch is kinda instant.

I made switcher that will just switch and replacer, that will kill the initial session, because I usually call my alias from an empty terminal anyway. Hopefully I will have time later to document it and release.

Thanks for the help.