feat: make ctrlc available to plugins (#13181)

# Description

This PR adds a new method to `EngineInterface`: `register_ctrlc_handler`
which takes a closure to run when the plugin's driving engine receives a
ctrlc-signal. It also adds a mirror of the `signals` attribute from the
main shell `EngineState`.

This is an example of how a plugin which makes a long poll http request
can end the request on ctrlc:
https://github.com/cablehead/nu_plugin_http/blob/main/src/commands/request.rs#L68-L77

To facilitate the feature, a new attribute has been added to
`EngineState`: `ctrlc_handlers`. This is a Vec of closures that will be
run when the engine's process receives a ctrlc signal.

When plugins are added to an `engine_state` during a `merge_delta`, the
engine passes the ctrlc_handlers to the plugin's
`.configure_ctrlc_handler` method, which gives the plugin a chance to
register a handler that sends a ctrlc packet through the
`PluginInterface`, if an instance of the plugin is currently running.

On the plugin side: `EngineInterface` also has a ctrlc_handlers Vec of
closures. Plugin calls can use `register_ctrlc_handler` to register a
closure that will be called in the plugin process when the
PluginInput::Ctrlc command is received.

For future reference these are some alternate places that were
investigated for tying the ctrlc trigger to transmitting a Ctrlc packet
through the `PluginInterface`:

- Directly from `src/signals.rs`: the handler there would need a
reference to the Vec<Arc<RegisteredPlugins>>, which would require us to
wrap the plugins in a Mutex, which we don't want to do.

- have `PersistentPlugin.get_plugin` pass down the engine's
CtrlcHandlers to .get and then to .spawn (if the plugin isn't already
running). Once we have CtrlcHandlers in spawn, we can register a handler
to write directly to PluginInterface. We don't want to double down on
passing engine_state to spawn this way though, as it's unpredictable
because it would depend on whether the plugin has already been spawned
or not.

- pass `ctrlc_handlers` to PersistentPlugin::new so it can store it on
itself so it's available to spawn.

- in `PersistentPlugin.spawn`, create a handler that sends to a clone of
the GC event loop's tx. this has the same issues with regards to how to
get CtrlcHandlers to the spawn method, and is more complicated than a
handler that writes directly to PluginInterface

# User-Facing Changes

No breaking changes

---------

Co-authored-by: Ian Manske <ian.manske@pm.me>
This commit is contained in:
Andy Gayton
2024-07-30 09:29:18 -04:00
committed by GitHub
parent e3f78b8793
commit 7b82c6b482
17 changed files with 310 additions and 21 deletions

View File

@ -0,0 +1,50 @@
use std::sync::mpsc;
use nu_plugin::{EngineInterface, EvaluatedCall, PluginCommand};
use nu_protocol::{Category, LabeledError, PipelineData, Signature};
use crate::ExamplePlugin;
/// `example ctrlc`
pub struct Ctrlc;
impl PluginCommand for Ctrlc {
type Plugin = ExamplePlugin;
fn name(&self) -> &str {
"example ctrlc"
}
fn usage(&self) -> &str {
"Example command that demonstrates registering a ctrl-c handler"
}
fn signature(&self) -> Signature {
Signature::build(self.name()).category(Category::Experimental)
}
fn search_terms(&self) -> Vec<&str> {
vec!["example"]
}
fn run(
&self,
_plugin: &ExamplePlugin,
engine: &EngineInterface,
_call: &EvaluatedCall,
_input: PipelineData,
) -> Result<PipelineData, LabeledError> {
let (sender, receiver) = mpsc::channel::<()>();
let _guard = engine.register_ctrlc_handler(Box::new(move || {
let _ = sender.send(());
}));
eprintln!("interrupt status: {:?}", engine.signals().interrupted());
eprintln!("waiting for ctrl-c signal...");
receiver.recv().expect("handler went away");
eprintln!("interrupt status: {:?}", engine.signals().interrupted());
eprintln!("peace.");
Ok(PipelineData::Empty)
}
}

View File

@ -15,12 +15,14 @@ pub use two::Two;
// Engine interface demos
mod call_decl;
mod config;
mod ctrlc;
mod disable_gc;
mod env;
mod view_span;
pub use call_decl::CallDecl;
pub use config::Config;
pub use ctrlc::Ctrlc;
pub use disable_gc::DisableGc;
pub use env::Env;
pub use view_span::ViewSpan;

View File

@ -27,6 +27,7 @@ impl Plugin for ExamplePlugin {
Box::new(Env),
Box::new(ViewSpan),
Box::new(DisableGc),
Box::new(Ctrlc),
Box::new(CallDecl),
// Stream demos
Box::new(CollectBytes),