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use std::{
cmp::Ordering,
collections::HashMap,
env,
ffi::OsString,
ops::Deref,
panic::AssertUnwindSafe,
sync::mpsc::{self, TrySendError},
thread,
};
use nu_engine::documentation::get_flags_section;
use nu_plugin_core::{
ClientCommunicationIo, CommunicationMode, InterfaceManager, PluginEncoder, PluginRead,
PluginWrite,
};
use nu_plugin_protocol::{CallInfo, CustomValueOp, PluginCustomValue, PluginInput, PluginOutput};
use nu_protocol::{
ast::Operator, CustomValue, IntoSpanned, LabeledError, PipelineData, ShellError, Spanned, Value,
};
use thiserror::Error;
use self::{command::render_examples, interface::ReceivedPluginCall};
mod command;
mod interface;
pub use command::{create_plugin_signature, PluginCommand, SimplePluginCommand};
pub use interface::{EngineInterface, EngineInterfaceManager};
/// This should be larger than the largest commonly sent message to avoid excessive fragmentation.
///
/// The buffers coming from byte streams are typically each 8192 bytes, so double that.
#[allow(dead_code)]
pub(crate) const OUTPUT_BUFFER_SIZE: usize = 16384;
/// The API for a Nushell plugin
///
/// A plugin defines multiple commands, which are added to the engine when the user calls
/// `register`.
///
/// The plugin must be able to be safely shared between threads, so that multiple invocations can
/// be run in parallel. If interior mutability is desired, consider synchronization primitives such
/// as [mutexes](std::sync::Mutex) and [channels](std::sync::mpsc).
///
/// # Examples
/// Basic usage:
/// ```
/// # use nu_plugin::*;
/// # use nu_protocol::{LabeledError, Signature, Type, Value};
/// struct HelloPlugin;
/// struct Hello;
///
/// impl Plugin for HelloPlugin {
/// fn commands(&self) -> Vec<Box<dyn PluginCommand<Plugin=Self>>> {
/// vec![Box::new(Hello)]
/// }
/// }
///
/// impl SimplePluginCommand for Hello {
/// type Plugin = HelloPlugin;
///
/// fn name(&self) -> &str {
/// "hello"
/// }
///
/// fn usage(&self) -> &str {
/// "Every programmer's favorite greeting"
/// }
///
/// fn signature(&self) -> Signature {
/// Signature::build(PluginCommand::name(self))
/// .input_output_type(Type::Nothing, Type::String)
/// }
///
/// fn run(
/// &self,
/// plugin: &HelloPlugin,
/// engine: &EngineInterface,
/// call: &EvaluatedCall,
/// input: &Value,
/// ) -> Result<Value, LabeledError> {
/// Ok(Value::string("Hello, World!".to_owned(), call.head))
/// }
/// }
///
/// # fn main() {
/// # serve_plugin(&HelloPlugin{}, MsgPackSerializer)
/// # }
/// ```
pub trait Plugin: Sync {
/// The commands supported by the plugin
///
/// Each [`PluginCommand`] contains both the signature of the command and the functionality it
/// implements.
///
/// This is only called once by [`serve_plugin`] at the beginning of your plugin's execution. It
/// is not possible to change the defined commands during runtime.
fn commands(&self) -> Vec<Box<dyn PluginCommand<Plugin = Self>>>;
/// Collapse a custom value to plain old data.
///
/// The default implementation of this method just calls [`CustomValue::to_base_value`], but
/// the method can be implemented differently if accessing plugin state is desirable.
fn custom_value_to_base_value(
&self,
engine: &EngineInterface,
custom_value: Spanned<Box<dyn CustomValue>>,
) -> Result<Value, LabeledError> {
let _ = engine;
custom_value
.item
.to_base_value(custom_value.span)
.map_err(LabeledError::from)
}
/// Follow a numbered cell path on a custom value - e.g. `value.0`.
///
/// The default implementation of this method just calls [`CustomValue::follow_path_int`], but
/// the method can be implemented differently if accessing plugin state is desirable.
fn custom_value_follow_path_int(
&self,
engine: &EngineInterface,
custom_value: Spanned<Box<dyn CustomValue>>,
index: Spanned<usize>,
) -> Result<Value, LabeledError> {
let _ = engine;
custom_value
.item
.follow_path_int(custom_value.span, index.item, index.span)
.map_err(LabeledError::from)
}
/// Follow a named cell path on a custom value - e.g. `value.column`.
///
/// The default implementation of this method just calls [`CustomValue::follow_path_string`],
/// but the method can be implemented differently if accessing plugin state is desirable.
fn custom_value_follow_path_string(
&self,
engine: &EngineInterface,
custom_value: Spanned<Box<dyn CustomValue>>,
column_name: Spanned<String>,
) -> Result<Value, LabeledError> {
let _ = engine;
custom_value
.item
.follow_path_string(custom_value.span, column_name.item, column_name.span)
.map_err(LabeledError::from)
}
/// Implement comparison logic for custom values.
///
/// The default implementation of this method just calls [`CustomValue::partial_cmp`], but
/// the method can be implemented differently if accessing plugin state is desirable.
///
/// Note that returning an error here is unlikely to produce desired behavior, as `partial_cmp`
/// lacks a way to produce an error. At the moment the engine just logs the error, and the
/// comparison returns `None`.
fn custom_value_partial_cmp(
&self,
engine: &EngineInterface,
custom_value: Box<dyn CustomValue>,
other_value: Value,
) -> Result<Option<Ordering>, LabeledError> {
let _ = engine;
Ok(custom_value.partial_cmp(&other_value))
}
/// Implement functionality for an operator on a custom value.
///
/// The default implementation of this method just calls [`CustomValue::operation`], but
/// the method can be implemented differently if accessing plugin state is desirable.
fn custom_value_operation(
&self,
engine: &EngineInterface,
left: Spanned<Box<dyn CustomValue>>,
operator: Spanned<Operator>,
right: Value,
) -> Result<Value, LabeledError> {
let _ = engine;
left.item
.operation(left.span, operator.item, operator.span, &right)
.map_err(LabeledError::from)
}
/// Handle a notification that all copies of a custom value within the engine have been dropped.
///
/// This notification is only sent if [`CustomValue::notify_plugin_on_drop`] was true. Unlike
/// the other custom value handlers, a span is not provided.
///
/// Note that a new custom value is created each time it is sent to the engine - if you intend
/// to accept a custom value and send it back, you may need to implement some kind of unique
/// reference counting in your plugin, as you will receive multiple drop notifications even if
/// the data within is identical.
///
/// The default implementation does nothing. Any error generated here is unlikely to be visible
/// to the user, and will only show up in the engine's log output.
fn custom_value_dropped(
&self,
engine: &EngineInterface,
custom_value: Box<dyn CustomValue>,
) -> Result<(), LabeledError> {
let _ = (engine, custom_value);
Ok(())
}
}
/// Function used to implement the communication protocol between nushell and an external plugin.
///
/// When creating a new plugin this function is typically used as the main entry
/// point for the plugin, e.g.
///
/// ```rust,no_run
/// # use nu_plugin::*;
/// # use nu_protocol::{PluginSignature, Value};
/// # struct MyPlugin;
/// # impl MyPlugin { fn new() -> Self { Self }}
/// # impl Plugin for MyPlugin {
/// # fn commands(&self) -> Vec<Box<dyn PluginCommand<Plugin=Self>>> {todo!();}
/// # }
/// fn main() {
/// serve_plugin(&MyPlugin::new(), MsgPackSerializer)
/// }
/// ```
pub fn serve_plugin(plugin: &impl Plugin, encoder: impl PluginEncoder + 'static) {
let args: Vec<OsString> = env::args_os().skip(1).collect();
// Determine the plugin name, for errors
let exe = std::env::current_exe().ok();
let plugin_name: String = exe
.as_ref()
.and_then(|path| path.file_stem())
.map(|stem| stem.to_string_lossy().into_owned())
.map(|stem| {
stem.strip_prefix("nu_plugin_")
.map(|s| s.to_owned())
.unwrap_or(stem)
})
.unwrap_or_else(|| "(unknown)".into());
if args.is_empty() || args[0] == "-h" || args[0] == "--help" {
print_help(plugin, encoder);
std::process::exit(0)
}
// Implement different communication modes:
let mode = if args[0] == "--stdio" && args.len() == 1 {
// --stdio always supported.
CommunicationMode::Stdio
} else if args[0] == "--local-socket" && args.len() == 2 {
#[cfg(feature = "local-socket")]
{
CommunicationMode::LocalSocket((&args[1]).into())
}
#[cfg(not(feature = "local-socket"))]
{
eprintln!("{plugin_name}: local socket mode is not supported");
std::process::exit(1);
}
} else {
eprintln!(
"{}: This plugin must be run from within Nushell. See `plugin add --help` for details \
on how to use plugins.",
env::current_exe()
.map(|path| path.display().to_string())
.unwrap_or_else(|_| "plugin".into())
);
eprintln!(
"If you are running from Nushell, this plugin may be incompatible with the \
version of nushell you are using."
);
std::process::exit(1)
};
let encoder_clone = encoder.clone();
let result = match mode.connect_as_client() {
Ok(ClientCommunicationIo::Stdio(stdin, mut stdout)) => {
tell_nushell_encoding(&mut stdout, &encoder).expect("failed to tell nushell encoding");
serve_plugin_io(
plugin,
&plugin_name,
move || (stdin.lock(), encoder_clone),
move || (stdout, encoder),
)
}
#[cfg(feature = "local-socket")]
Ok(ClientCommunicationIo::LocalSocket {
read_in,
mut write_out,
}) => {
use std::io::{BufReader, BufWriter};
use std::sync::Mutex;
tell_nushell_encoding(&mut write_out, &encoder)
.expect("failed to tell nushell encoding");
let read = BufReader::with_capacity(OUTPUT_BUFFER_SIZE, read_in);
let write = Mutex::new(BufWriter::with_capacity(OUTPUT_BUFFER_SIZE, write_out));
serve_plugin_io(
plugin,
&plugin_name,
move || (read, encoder_clone),
move || (write, encoder),
)
}
Err(err) => {
eprintln!("{plugin_name}: failed to connect: {err:?}");
std::process::exit(1);
}
};
match result {
Ok(()) => (),
// Write unreported errors to the console
Err(ServePluginError::UnreportedError(err)) => {
eprintln!("Plugin `{plugin_name}` error: {err}");
std::process::exit(1);
}
Err(_) => std::process::exit(1),
}
}
fn tell_nushell_encoding(
writer: &mut impl std::io::Write,
encoder: &impl PluginEncoder,
) -> Result<(), std::io::Error> {
// tell nushell encoding.
//
// 1 byte
// encoding format: | content-length | content |
let encoding = encoder.name();
let length = encoding.len() as u8;
let mut encoding_content: Vec<u8> = encoding.as_bytes().to_vec();
encoding_content.insert(0, length);
writer.write_all(&encoding_content)?;
writer.flush()
}
/// An error from [`serve_plugin_io()`]
#[derive(Debug, Error)]
pub enum ServePluginError {
/// An error occurred that could not be reported to the engine.
#[error("{0}")]
UnreportedError(#[source] ShellError),
/// An error occurred that could be reported to the engine.
#[error("{0}")]
ReportedError(#[source] ShellError),
/// A version mismatch occurred.
#[error("{0}")]
Incompatible(#[source] ShellError),
/// An I/O error occurred.
#[error("{0}")]
IOError(#[source] ShellError),
/// A thread spawning error occurred.
#[error("{0}")]
ThreadSpawnError(#[source] std::io::Error),
/// A panic occurred.
#[error("a panic occurred in a plugin thread")]
Panicked,
}
impl From<ShellError> for ServePluginError {
fn from(error: ShellError) -> Self {
match error {
ShellError::IOError { .. } => ServePluginError::IOError(error),
ShellError::PluginFailedToLoad { .. } => ServePluginError::Incompatible(error),
_ => ServePluginError::UnreportedError(error),
}
}
}
/// Convert result error to ReportedError if it can be reported to the engine.
trait TryToReport {
type T;
fn try_to_report(self, engine: &EngineInterface) -> Result<Self::T, ServePluginError>;
}
impl<T, E> TryToReport for Result<T, E>
where
E: Into<ServePluginError>,
{
type T = T;
fn try_to_report(self, engine: &EngineInterface) -> Result<T, ServePluginError> {
self.map_err(|e| match e.into() {
ServePluginError::UnreportedError(err) => {
if engine.write_response(Err(err.clone())).is_ok() {
ServePluginError::ReportedError(err)
} else {
ServePluginError::UnreportedError(err)
}
}
other => other,
})
}
}
/// Serve a plugin on the given input & output.
///
/// Unlike [`serve_plugin`], this doesn't assume total control over the process lifecycle / stdin /
/// stdout, and can be used for more advanced use cases.
///
/// This is not a public API.
#[doc(hidden)]
pub fn serve_plugin_io<I, O>(
plugin: &impl Plugin,
plugin_name: &str,
input: impl FnOnce() -> I + Send + 'static,
output: impl FnOnce() -> O + Send + 'static,
) -> Result<(), ServePluginError>
where
I: PluginRead<PluginInput> + 'static,
O: PluginWrite<PluginOutput> + 'static,
{
let (error_tx, error_rx) = mpsc::channel();
// Build commands map, to make running a command easier
let mut commands: HashMap<String, _> = HashMap::new();
for command in plugin.commands() {
if let Some(previous) = commands.insert(command.name().into(), command) {
eprintln!(
"Plugin `{plugin_name}` warning: command `{}` shadowed by another command with the \
same name. Check your commands' `name()` methods",
previous.name()
);
}
}
let mut manager = EngineInterfaceManager::new(output());
let call_receiver = manager
.take_plugin_call_receiver()
// This expect should be totally safe, as we just created the manager
.expect("take_plugin_call_receiver returned None");
// We need to hold on to the interface to keep the manager alive. We can drop it at the end
let interface = manager.get_interface();
// Send Hello message
interface.hello()?;
{
// Spawn the reader thread
let error_tx = error_tx.clone();
std::thread::Builder::new()
.name("engine interface reader".into())
.spawn(move || {
// Report the error on the channel if we get an error
if let Err(err) = manager.consume_all(input()) {
let _ = error_tx.send(ServePluginError::from(err));
}
})
.map_err(ServePluginError::ThreadSpawnError)?;
}
// Handle each Run plugin call on a thread
thread::scope(|scope| {
let run = |engine, call_info| {
// SAFETY: It should be okay to use `AssertUnwindSafe` here, because we don't use any
// of the references after we catch the unwind, and immediately exit.
let unwind_result = std::panic::catch_unwind(AssertUnwindSafe(|| {
let CallInfo { name, call, input } = call_info;
let result = if let Some(command) = commands.get(&name) {
command.run(plugin, &engine, &call, input)
} else {
Err(
LabeledError::new(format!("Plugin command not found: `{name}`"))
.with_label(
format!("plugin `{plugin_name}` doesn't have this command"),
call.head,
),
)
};
let write_result = engine
.write_response(result)
.and_then(|writer| writer.write())
.try_to_report(&engine);
if let Err(err) = write_result {
let _ = error_tx.send(err);
}
}));
if unwind_result.is_err() {
// Exit after unwind if a panic occurred
std::process::exit(1);
}
};
// As an optimization: create one thread that can be reused for Run calls in sequence
let (run_tx, run_rx) = mpsc::sync_channel(0);
thread::Builder::new()
.name("plugin runner (primary)".into())
.spawn_scoped(scope, move || {
for (engine, call) in run_rx {
run(engine, call);
}
})
.map_err(ServePluginError::ThreadSpawnError)?;
for plugin_call in call_receiver {
// Check for pending errors
if let Ok(error) = error_rx.try_recv() {
return Err(error);
}
match plugin_call {
// Sending the signature back to nushell to create the declaration definition
ReceivedPluginCall::Signature { engine } => {
let sigs = commands
.values()
.map(|command| create_plugin_signature(command.deref()))
.map(|mut sig| {
render_examples(plugin, &engine, &mut sig.examples)?;
Ok(sig)
})
.collect::<Result<Vec<_>, ShellError>>()
.try_to_report(&engine)?;
engine.write_signature(sigs).try_to_report(&engine)?;
}
// Run the plugin on a background thread, handling any input or output streams
ReceivedPluginCall::Run { engine, call } => {
// Try to run it on the primary thread
match run_tx.try_send((engine, call)) {
Ok(()) => (),
// If the primary thread isn't ready, spawn a secondary thread to do it
Err(TrySendError::Full((engine, call)))
| Err(TrySendError::Disconnected((engine, call))) => {
thread::Builder::new()
.name("plugin runner (secondary)".into())
.spawn_scoped(scope, move || run(engine, call))
.map_err(ServePluginError::ThreadSpawnError)?;
}
}
}
// Do an operation on a custom value
ReceivedPluginCall::CustomValueOp {
engine,
custom_value,
op,
} => {
custom_value_op(plugin, &engine, custom_value, op).try_to_report(&engine)?;
}
}
}
Ok::<_, ServePluginError>(())
})?;
// This will stop the manager
drop(interface);
// Receive any error left on the channel
if let Ok(err) = error_rx.try_recv() {
Err(err)
} else {
Ok(())
}
}
fn custom_value_op(
plugin: &impl Plugin,
engine: &EngineInterface,
custom_value: Spanned<PluginCustomValue>,
op: CustomValueOp,
) -> Result<(), ShellError> {
let local_value = custom_value
.item
.deserialize_to_custom_value(custom_value.span)?
.into_spanned(custom_value.span);
match op {
CustomValueOp::ToBaseValue => {
let result = plugin
.custom_value_to_base_value(engine, local_value)
.map(|value| PipelineData::Value(value, None));
engine
.write_response(result)
.and_then(|writer| writer.write())
}
CustomValueOp::FollowPathInt(index) => {
let result = plugin
.custom_value_follow_path_int(engine, local_value, index)
.map(|value| PipelineData::Value(value, None));
engine
.write_response(result)
.and_then(|writer| writer.write())
}
CustomValueOp::FollowPathString(column_name) => {
let result = plugin
.custom_value_follow_path_string(engine, local_value, column_name)
.map(|value| PipelineData::Value(value, None));
engine
.write_response(result)
.and_then(|writer| writer.write())
}
CustomValueOp::PartialCmp(mut other_value) => {
PluginCustomValue::deserialize_custom_values_in(&mut other_value)?;
match plugin.custom_value_partial_cmp(engine, local_value.item, other_value) {
Ok(ordering) => engine.write_ordering(ordering),
Err(err) => engine
.write_response(Err(err))
.and_then(|writer| writer.write()),
}
}
CustomValueOp::Operation(operator, mut right) => {
PluginCustomValue::deserialize_custom_values_in(&mut right)?;
let result = plugin
.custom_value_operation(engine, local_value, operator, right)
.map(|value| PipelineData::Value(value, None));
engine
.write_response(result)
.and_then(|writer| writer.write())
}
CustomValueOp::Dropped => {
let result = plugin
.custom_value_dropped(engine, local_value.item)
.map(|_| PipelineData::Empty);
engine
.write_response(result)
.and_then(|writer| writer.write())
}
}
}
fn print_help(plugin: &impl Plugin, encoder: impl PluginEncoder) {
use std::fmt::Write;
println!("Nushell Plugin");
println!("Encoder: {}", encoder.name());
let mut help = String::new();
plugin.commands().into_iter().for_each(|command| {
let signature = command.signature();
let res = write!(help, "\nCommand: {}", command.name())
.and_then(|_| writeln!(help, "\nUsage:\n > {}", command.usage()))
.and_then(|_| {
if !command.extra_usage().is_empty() {
writeln!(help, "\nExtra usage:\n > {}", command.extra_usage())
} else {
Ok(())
}
})
.and_then(|_| {
let flags = get_flags_section(None, &signature, |v| format!("{:#?}", v));
write!(help, "{flags}")
})
.and_then(|_| writeln!(help, "\nParameters:"))
.and_then(|_| {
signature
.required_positional
.iter()
.try_for_each(|positional| {
writeln!(
help,
" {} <{}>: {}",
positional.name, positional.shape, positional.desc
)
})
})
.and_then(|_| {
signature
.optional_positional
.iter()
.try_for_each(|positional| {
writeln!(
help,
" (optional) {} <{}>: {}",
positional.name, positional.shape, positional.desc
)
})
})
.and_then(|_| {
if let Some(rest_positional) = &signature.rest_positional {
writeln!(
help,
" ...{} <{}>: {}",
rest_positional.name, rest_positional.shape, rest_positional.desc
)
} else {
Ok(())
}
})
.and_then(|_| writeln!(help, "======================"));
if res.is_err() {
println!("{res:?}")
}
});
println!("{help}")
}