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mod declaration;
pub use declaration::PluginDeclaration;
use nu_engine::documentation::get_flags_section;
use std::collections::HashMap;
use std::ffi::OsStr;
use std::sync::{Arc, Mutex};
use crate::plugin::interface::{EngineInterfaceManager, ReceivedPluginCall};
use crate::protocol::{CallInfo, CustomValueOp, LabeledError, PluginInput, PluginOutput};
use crate::EncodingType;
use std::env;
use std::fmt::Write;
use std::io::{BufReader, Read, Write as WriteTrait};
use std::path::Path;
use std::process::{Child, ChildStdout, Command as CommandSys, Stdio};
use nu_protocol::{PipelineData, PluginSignature, ShellError, Value};
mod interface;
pub(crate) use interface::PluginInterface;
mod context;
pub(crate) use context::PluginExecutionCommandContext;
mod identity;
pub(crate) use identity::PluginIdentity;
use self::interface::{InterfaceManager, PluginInterfaceManager};
use super::EvaluatedCall;
pub(crate) const OUTPUT_BUFFER_SIZE: usize = 8192;
/// Encoder for a specific message type. Usually implemented on [`PluginInput`]
/// and [`PluginOutput`].
#[doc(hidden)]
pub trait Encoder<T>: Clone + Send + Sync {
/// Serialize a value in the [`PluginEncoder`]s format
///
/// Returns [ShellError::IOError] if there was a problem writing, or
/// [ShellError::PluginFailedToEncode] for a serialization error.
#[doc(hidden)]
fn encode(&self, data: &T, writer: &mut impl std::io::Write) -> Result<(), ShellError>;
/// Deserialize a value from the [`PluginEncoder`]'s format
///
/// Returns `None` if there is no more output to receive.
///
/// Returns [ShellError::IOError] if there was a problem reading, or
/// [ShellError::PluginFailedToDecode] for a deserialization error.
#[doc(hidden)]
fn decode(&self, reader: &mut impl std::io::BufRead) -> Result<Option<T>, ShellError>;
}
/// Encoding scheme that defines a plugin's communication protocol with Nu
pub trait PluginEncoder: Encoder<PluginInput> + Encoder<PluginOutput> {
/// The name of the encoder (e.g., `json`)
fn name(&self) -> &str;
}
fn create_command(path: &Path, shell: Option<&Path>) -> CommandSys {
log::trace!("Starting plugin: {path:?}, shell = {shell:?}");
// There is only one mode supported at the moment, but the idea is that future
// communication methods could be supported if desirable
let mut input_arg = Some("--stdio");
let mut process = match (path.extension(), shell) {
(_, Some(shell)) => {
let mut process = std::process::Command::new(shell);
process.arg(path);
process
}
(Some(extension), None) => {
let (shell, command_switch) = match extension.to_str() {
Some("cmd") | Some("bat") => (Some("cmd"), Some("/c")),
Some("sh") => (Some("sh"), Some("-c")),
Some("py") => (Some("python"), None),
_ => (None, None),
};
match (shell, command_switch) {
(Some(shell), Some(command_switch)) => {
let mut process = std::process::Command::new(shell);
process.arg(command_switch);
// If `command_switch` is set, we need to pass the path + arg as one argument
// e.g. sh -c "nu_plugin_inc --stdio"
let mut combined = path.as_os_str().to_owned();
if let Some(arg) = input_arg.take() {
combined.push(OsStr::new(" "));
combined.push(OsStr::new(arg));
}
process.arg(combined);
process
}
(Some(shell), None) => {
let mut process = std::process::Command::new(shell);
process.arg(path);
process
}
_ => std::process::Command::new(path),
}
}
(None, None) => std::process::Command::new(path),
};
// Pass input_arg, unless we consumed it already
if let Some(input_arg) = input_arg {
process.arg(input_arg);
}
// Both stdout and stdin are piped so we can receive information from the plugin
process.stdout(Stdio::piped()).stdin(Stdio::piped());
process
}
fn make_plugin_interface(
mut child: Child,
identity: Arc<PluginIdentity>,
) -> Result<PluginInterface, ShellError> {
let stdin = child
.stdin
.take()
.ok_or_else(|| ShellError::PluginFailedToLoad {
msg: "Plugin missing stdin writer".into(),
})?;
let mut stdout = child
.stdout
.take()
.ok_or_else(|| ShellError::PluginFailedToLoad {
msg: "Plugin missing stdout writer".into(),
})?;
let encoder = get_plugin_encoding(&mut stdout)?;
let reader = BufReader::with_capacity(OUTPUT_BUFFER_SIZE, stdout);
let mut manager = PluginInterfaceManager::new(identity, (Mutex::new(stdin), encoder));
let interface = manager.get_interface();
interface.hello()?;
// Spawn the reader on a new thread. We need to be able to read messages at the same time that
// we write, because we are expected to be able to handle multiple messages coming in from the
// plugin at any time, including stream messages like `Drop`.
std::thread::Builder::new()
.name("plugin interface reader".into())
.spawn(move || {
if let Err(err) = manager.consume_all((reader, encoder)) {
log::warn!("Error in PluginInterfaceManager: {err}");
}
// If the loop has ended, drop the manager so everyone disconnects and then wait for the
// child to exit
drop(manager);
let _ = child.wait();
})
.map_err(|err| ShellError::PluginFailedToLoad {
msg: format!("Failed to spawn thread for plugin: {err}"),
})?;
Ok(interface)
}
#[doc(hidden)] // Note: not for plugin authors / only used in nu-parser
pub fn get_signature(
path: &Path,
shell: Option<&Path>,
current_envs: &HashMap<String, String>,
) -> Result<Vec<PluginSignature>, ShellError> {
Arc::new(PluginIdentity::new(path, shell.map(|s| s.to_owned())))
.spawn(current_envs)?
.get_signature()
}
/// The basic API for a Nushell plugin
///
/// This is the trait that Nushell plugins must implement. The methods defined on
/// `Plugin` are invoked by [serve_plugin] during plugin registration and execution.
///
/// If large amounts of data are expected to need to be received or produced, it may be more
/// appropriate to implement [StreamingPlugin] instead.
///
/// # Examples
/// Basic usage:
/// ```
/// # use nu_plugin::*;
/// # use nu_protocol::{PluginSignature, Type, Value};
/// struct HelloPlugin;
///
/// impl Plugin for HelloPlugin {
/// fn signature(&self) -> Vec<PluginSignature> {
/// let sig = PluginSignature::build("hello")
/// .input_output_type(Type::Nothing, Type::String);
///
/// vec![sig]
/// }
///
/// fn run(
/// &mut self,
/// name: &str,
/// config: &Option<Value>,
/// call: &EvaluatedCall,
/// input: &Value,
/// ) -> Result<Value, LabeledError> {
/// Ok(Value::string("Hello, World!".to_owned(), call.head))
/// }
/// }
///
/// # fn main() {
/// # serve_plugin(&mut HelloPlugin{}, MsgPackSerializer)
/// # }
/// ```
pub trait Plugin {
/// The signature of the plugin
///
/// This method returns the [PluginSignature]s that describe the capabilities
/// of this plugin. Since a single plugin executable can support multiple invocation
/// patterns we return a `Vec` of signatures.
fn signature(&self) -> Vec<PluginSignature>;
/// Perform the actual behavior of the plugin
///
/// The behavior of the plugin is defined by the implementation of this method.
/// When Nushell invoked the plugin [serve_plugin] will call this method and
/// print the serialized returned value or error to stdout, which Nushell will
/// interpret.
///
/// The `name` is only relevant for plugins that implement multiple commands as the
/// invoked command will be passed in via this argument. The `call` contains
/// metadata describing how the plugin was invoked and `input` contains the structured
/// data passed to the command implemented by this [Plugin].
///
/// This variant does not support streaming. Consider implementing [StreamingPlugin] instead
/// if streaming is desired.
fn run(
&mut self,
name: &str,
config: &Option<Value>,
call: &EvaluatedCall,
input: &Value,
) -> Result<Value, LabeledError>;
}
/// The streaming API for a Nushell plugin
///
/// This is a more low-level version of the [Plugin] trait that supports operating on streams of
/// data. If you don't need to operate on streams, consider using that trait instead.
///
/// The methods defined on `StreamingPlugin` are invoked by [serve_plugin] during plugin
/// registration and execution.
///
/// # Examples
/// Basic usage:
/// ```
/// # use nu_plugin::*;
/// # use nu_protocol::{PluginSignature, PipelineData, Type, Value};
/// struct LowercasePlugin;
///
/// impl StreamingPlugin for LowercasePlugin {
/// fn signature(&self) -> Vec<PluginSignature> {
/// let sig = PluginSignature::build("lowercase")
/// .usage("Convert each string in a stream to lowercase")
/// .input_output_type(Type::List(Type::String.into()), Type::List(Type::String.into()));
///
/// vec![sig]
/// }
///
/// fn run(
/// &mut self,
/// name: &str,
/// config: &Option<Value>,
/// call: &EvaluatedCall,
/// input: PipelineData,
/// ) -> Result<PipelineData, LabeledError> {
/// let span = call.head;
/// Ok(input.map(move |value| {
/// value.as_str()
/// .map(|string| Value::string(string.to_lowercase(), span))
/// // Errors in a stream should be returned as values.
/// .unwrap_or_else(|err| Value::error(err, span))
/// }, None)?)
/// }
/// }
///
/// # fn main() {
/// # serve_plugin(&mut LowercasePlugin{}, MsgPackSerializer)
/// # }
/// ```
pub trait StreamingPlugin {
/// The signature of the plugin
///
/// This method returns the [PluginSignature]s that describe the capabilities
/// of this plugin. Since a single plugin executable can support multiple invocation
/// patterns we return a `Vec` of signatures.
fn signature(&self) -> Vec<PluginSignature>;
/// Perform the actual behavior of the plugin
///
/// The behavior of the plugin is defined by the implementation of this method.
/// When Nushell invoked the plugin [serve_plugin] will call this method and
/// print the serialized returned value or error to stdout, which Nushell will
/// interpret.
///
/// The `name` is only relevant for plugins that implement multiple commands as the
/// invoked command will be passed in via this argument. The `call` contains
/// metadata describing how the plugin was invoked and `input` contains the structured
/// data passed to the command implemented by this [Plugin].
///
/// This variant expects to receive and produce [PipelineData], which allows for stream-based
/// handling of I/O. This is recommended if the plugin is expected to transform large lists or
/// potentially large quantities of bytes. The API is more complex however, and [Plugin] is
/// recommended instead if this is not a concern.
fn run(
&mut self,
name: &str,
config: &Option<Value>,
call: &EvaluatedCall,
input: PipelineData,
) -> Result<PipelineData, LabeledError>;
}
/// All [Plugin]s can be used as [StreamingPlugin]s, but input streams will be fully consumed
/// before the plugin runs.
impl<T: Plugin> StreamingPlugin for T {
fn signature(&self) -> Vec<PluginSignature> {
<Self as Plugin>::signature(self)
}
fn run(
&mut self,
name: &str,
config: &Option<Value>,
call: &EvaluatedCall,
input: PipelineData,
) -> Result<PipelineData, LabeledError> {
// Unwrap the PipelineData from input, consuming the potential stream, and pass it to the
// simpler signature in Plugin
let span = input.span().unwrap_or(call.head);
let input_value = input.into_value(span);
// Wrap the output in PipelineData::Value
<Self as Plugin>::run(self, name, config, call, &input_value)
.map(|value| PipelineData::Value(value, None))
}
}
/// Function used to implement the communication protocol between
/// nushell and an external plugin. Both [Plugin] and [StreamingPlugin] are supported.
///
/// 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 signature(&self) -> Vec<PluginSignature> {todo!();}
/// # fn run(&mut self, name: &str, config: &Option<Value>, call: &EvaluatedCall, input: &Value)
/// # -> Result<Value, LabeledError> {todo!();}
/// # }
/// fn main() {
/// serve_plugin(&mut MyPlugin::new(), MsgPackSerializer)
/// }
/// ```
pub fn serve_plugin(plugin: &mut impl StreamingPlugin, encoder: impl PluginEncoder + 'static) {
let mut args = env::args().skip(1);
let number_of_args = args.len();
let first_arg = args.next();
if number_of_args == 0
|| first_arg
.as_ref()
.is_some_and(|arg| arg == "-h" || arg == "--help")
{
print_help(plugin, encoder);
std::process::exit(0)
}
// Must pass --stdio for plugin execution. Any other arg is an error to give us options in the
// future.
if number_of_args > 1 || !first_arg.is_some_and(|arg| arg == "--stdio") {
eprintln!(
"{}: This plugin must be run from within Nushell.",
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)
}
// tell nushell encoding.
//
// 1 byte
// encoding format: | content-length | content |
let mut stdout = std::io::stdout();
{
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);
stdout
.write_all(&encoding_content)
.expect("Failed to tell nushell my encoding");
stdout
.flush()
.expect("Failed to tell nushell my encoding when flushing stdout");
}
let mut manager = EngineInterfaceManager::new((stdout, encoder.clone()));
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();
// 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());
// Try an operation that could result in ShellError. Exit if an I/O error is encountered.
// Try to report the error to nushell otherwise, and failing that, panic.
macro_rules! try_or_report {
($interface:expr, $expr:expr) => (match $expr {
Ok(val) => val,
// Just exit if there is an I/O error. Most likely this just means that nushell
// interrupted us. If not, the error probably happened on the other side too, so we
// don't need to also report it.
Err(ShellError::IOError { .. }) => std::process::exit(1),
// If there is another error, try to send it to nushell and then exit.
Err(err) => {
let _ = $interface.write_response(Err(err.clone())).unwrap_or_else(|_| {
// If we can't send it to nushell, panic with it so at least we get the output
panic!("Plugin `{plugin_name}`: {}", err)
});
std::process::exit(1)
}
})
}
// Send Hello message
try_or_report!(interface, interface.hello());
let plugin_name_clone = plugin_name.clone();
// Spawn the reader thread
std::thread::Builder::new()
.name("engine interface reader".into())
.spawn(move || {
if let Err(err) = manager.consume_all((std::io::stdin().lock(), encoder)) {
// Do our best to report the read error. Most likely there is some kind of
// incompatibility between the plugin and nushell, so it makes more sense to try to
// report it on stderr than to send something.
eprintln!("Plugin `{plugin_name_clone}` read error: {err}");
std::process::exit(1);
}
})
.unwrap_or_else(|err| {
// If we fail to spawn the reader thread, we should exit
eprintln!("Plugin `{plugin_name}` failed to launch: {err}");
std::process::exit(1);
});
for plugin_call in call_receiver {
match plugin_call {
// Sending the signature back to nushell to create the declaration definition
ReceivedPluginCall::Signature { engine } => {
try_or_report!(engine, engine.write_signature(plugin.signature()));
}
// Run the plugin, handling any input or output streams
ReceivedPluginCall::Run {
engine,
call:
CallInfo {
name,
config,
call,
input,
},
} => {
let result = plugin.run(&name, &config, &call, input);
let write_result = engine
.write_response(result)
.and_then(|writer| writer.write_background());
try_or_report!(engine, write_result);
}
// Do an operation on a custom value
ReceivedPluginCall::CustomValueOp {
engine,
custom_value,
op,
} => {
let local_value = try_or_report!(
engine,
custom_value
.item
.deserialize_to_custom_value(custom_value.span)
);
match op {
CustomValueOp::ToBaseValue => {
let result = local_value
.to_base_value(custom_value.span)
.map(|value| PipelineData::Value(value, None));
let write_result = engine
.write_response(result)
.and_then(|writer| writer.write_background());
try_or_report!(engine, write_result);
}
}
}
}
}
// This will stop the manager
drop(interface);
}
fn print_help(plugin: &mut impl StreamingPlugin, encoder: impl PluginEncoder) {
println!("Nushell Plugin");
println!("Encoder: {}", encoder.name());
let mut help = String::new();
plugin.signature().iter().for_each(|signature| {
let res = write!(help, "\nCommand: {}", signature.sig.name)
.and_then(|_| writeln!(help, "\nUsage:\n > {}", signature.sig.usage))
.and_then(|_| {
if !signature.sig.extra_usage.is_empty() {
writeln!(help, "\nExtra usage:\n > {}", signature.sig.extra_usage)
} else {
Ok(())
}
})
.and_then(|_| {
let flags = get_flags_section(None, &signature.sig, |v| format!("{:#?}", v));
write!(help, "{flags}")
})
.and_then(|_| writeln!(help, "\nParameters:"))
.and_then(|_| {
signature
.sig
.required_positional
.iter()
.try_for_each(|positional| {
writeln!(
help,
" {} <{}>: {}",
positional.name, positional.shape, positional.desc
)
})
})
.and_then(|_| {
signature
.sig
.optional_positional
.iter()
.try_for_each(|positional| {
writeln!(
help,
" (optional) {} <{}>: {}",
positional.name, positional.shape, positional.desc
)
})
})
.and_then(|_| {
if let Some(rest_positional) = &signature.sig.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}")
}
pub fn get_plugin_encoding(child_stdout: &mut ChildStdout) -> Result<EncodingType, ShellError> {
let mut length_buf = [0u8; 1];
child_stdout
.read_exact(&mut length_buf)
.map_err(|e| ShellError::PluginFailedToLoad {
msg: format!("unable to get encoding from plugin: {e}"),
})?;
let mut buf = vec![0u8; length_buf[0] as usize];
child_stdout
.read_exact(&mut buf)
.map_err(|e| ShellError::PluginFailedToLoad {
msg: format!("unable to get encoding from plugin: {e}"),
})?;
EncodingType::try_from_bytes(&buf).ok_or_else(|| {
let encoding_for_debug = String::from_utf8_lossy(&buf);
ShellError::PluginFailedToLoad {
msg: format!("get unsupported plugin encoding: {encoding_for_debug}"),
}
})
}