plugin call function

crates/nu-parser/src/parse_keywords.rs

@@ -1,4 +1,4 @@
-use nu_plugin::plugin::get_signature;
+use nu_plugin::plugin::{get_signature, PluginDeclaration};
 use nu_protocol::{
     ast::{Block, Call, Expr, Expression, ImportPatternMember, Pipeline, Statement},
     engine::StateWorkingSet,
@@ -887,12 +887,21 @@ pub fn parse_plugin(
                     if let Ok(filename) = String::from_utf8(name_expr.to_vec()) {
                         let source_file = Path::new(&filename);
 
-                        // get signature from plugin
-                        // create plugin command declaration (need struct impl Command)
-                        // store declaration in working set
-                        match get_signature(source_file) {
-                            Err(err) => Some(ParseError::PluginError(format!("{}", err))),
-                            Ok(_signature) => None,
+                        if source_file.exists() & source_file.is_file() {
+                            // get signature from plugin
+                            match get_signature(source_file) {
+                                Err(err) => Some(ParseError::PluginError(format!("{}", err))),
+                                Ok(signature) => {
+                                    // create plugin command declaration (need struct impl Command)
+                                    // store declaration in working set
+                                    let plugin_decl = PluginDeclaration::new(filename, signature);
+                                    working_set.add_decl(Box::new(plugin_decl));
+
+                                    None
+                                }
+                            }
+                        } else {
+                            Some(ParseError::FileNotFound(filename))
                         }
                     } else {
                         Some(ParseError::NonUtf8(spans[1]))

crates/nu-plugin/build.rs

@@ -1,7 +0,0 @@
-fn main() {
-    capnpc::CompilerCommand::new()
-        .src_prefix("schema")
-        .file("schema/plugin.capnp")
-        .run()
-        .expect("compiling schema");
-}

crates/nu-plugin/schema/plugin.capnp

@@ -4,6 +4,8 @@
 # This schema, together with the command capnp proto is used to generate
 # the rust file that defines the serialization/deserialization objects
 # required to comunicate with the plugins created for nushell
+# If you modify the schema remember to compile it to generate the corresponding
+# rust file and place that file into the main nu-plugin folder
 
 # Generic structs used as helpers for the encoding
 struct Option(T) {
@@ -121,7 +123,8 @@ struct PluginCall {
 
 struct PluginResponse {
 	union {
-		signature @0 :Signature;
-		value @1 :Value;
+		error @0 :Text;
+		signature @1 :Signature;
+		value @2 :Value;
 	}
 }

crates/nu-plugin/src/lib.rs

@@ -1,7 +1,6 @@
 pub mod plugin;
 pub mod plugin_call;
+pub mod plugin_capnp;
 pub mod serializers;
 
-pub mod plugin_capnp {
-    include!(concat!(env!("OUT_DIR"), "/plugin_capnp.rs"));
-}
+pub use plugin::{serve_plugin, Plugin};

crates/nu-plugin/src/plugin.rs

@@ -1,9 +1,13 @@
-use std::process::{Command, Stdio};
+use crate::plugin_call::{self, decode_call, encode_response};
+use std::io::BufReader;
+use std::process::{Command as CommandSys, Stdio};
 use std::{fmt::Display, path::Path};
 
+use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::{ast::Call, Signature, Value};
+use nu_protocol::{PipelineData, ShellError};
 
-//use nu_protocol::{ShellError, Value};
+const OUTPUT_BUFFER_SIZE: usize = 8192;
 
 #[derive(Debug)]
 pub struct CallInfo {
@@ -21,16 +25,15 @@ pub enum PluginCall {
 // Information received from the plugin
 #[derive(Debug)]
 pub enum PluginResponse {
+    Error(String),
     Signature(Box<Signature>),
     Value(Box<Value>),
 }
 
-/// The `Plugin` trait defines the API which plugins may use to "hook" into nushell.
-pub trait Plugin {}
-
 #[derive(Debug)]
 pub enum PluginError {
     MissingSignature,
+    UnableToGetStdout,
     UnableToSpawn(String),
     EncodingError(String),
     DecodingError(String),
@@ -40,6 +43,7 @@ impl Display for PluginError {
     fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
         match self {
             PluginError::MissingSignature => write!(f, "missing signature in plugin"),
+            PluginError::UnableToGetStdout => write!(f, "couldn't get stdout from child process"),
             PluginError::UnableToSpawn(err) => {
                 write!(f, "error in spawned child process: {}", err)
             }
@@ -53,7 +57,7 @@ impl Display for PluginError {
     }
 }
 
-pub fn get_signature(path: &Path) -> Result<Signature, PluginError> {
+pub fn get_signature(path: &Path) -> Result<Box<Signature>, PluginError> {
     let mut plugin_cmd = create_command(path);
 
     // Both stdout and stdin are piped so we can get the information from the plugin
@@ -63,29 +67,196 @@ pub fn get_signature(path: &Path) -> Result<Signature, PluginError> {
     match plugin_cmd.spawn() {
         Err(err) => Err(PluginError::UnableToSpawn(format!("{}", err))),
         Ok(mut child) => {
-            // create message to plugin to indicate signature
-            // send message to plugin
-            // deserialize message with signature
+            // Create message to plugin to indicate that signature is required and
+            // send call to plugin asking for signature
+            if let Some(mut stdin_writer) = child.stdin.take() {
+                plugin_call::encode_call(&PluginCall::Signature, &mut stdin_writer)?
+            }
+
+            // deserialize response from plugin to extract the signature
+            let signature = if let Some(stdout_reader) = child.stdout.take() {
+                let mut buf_read = BufReader::with_capacity(OUTPUT_BUFFER_SIZE, stdout_reader);
+                let response = plugin_call::decode_response(&mut buf_read)?;
+
+                match response {
+                    PluginResponse::Signature(sign) => Ok(sign),
+                    PluginResponse::Error(msg) => Err(PluginError::DecodingError(msg)),
+                    _ => Err(PluginError::DecodingError("signature not found".into())),
+                }
+            } else {
+                Err(PluginError::UnableToGetStdout)
+            }?;
+
             match child.wait() {
                 Err(err) => Err(PluginError::UnableToSpawn(format!("{}", err))),
-                Ok(_) => Ok(Signature::build("testing")),
+                Ok(_) => Ok(signature),
             }
         }
     }
 }
 
-fn create_command(path: &Path) -> Command {
+fn create_command(path: &Path) -> CommandSys {
     //TODO. The selection of shell could be modifiable from the config file.
     if cfg!(windows) {
-        let mut process = Command::new("cmd");
+        let mut process = CommandSys::new("cmd");
         process.arg("/c");
         process.arg(path);
 
         process
     } else {
-        let mut process = Command::new("sh");
+        let mut process = CommandSys::new("sh");
         process.arg("-c").arg(path);
 
         process
     }
 }
+
+#[derive(Debug, Clone)]
+pub struct PluginDeclaration {
+    name: String,
+    signature: Box<Signature>,
+    filename: String,
+}
+
+impl PluginDeclaration {
+    pub fn new(filename: String, signature: Box<Signature>) -> Self {
+        Self {
+            name: signature.name.clone(),
+            signature,
+            filename,
+        }
+    }
+}
+
+impl Command for PluginDeclaration {
+    fn name(&self) -> &str {
+        &self.name
+    }
+
+    fn signature(&self) -> Signature {
+        self.signature.as_ref().clone()
+    }
+
+    fn usage(&self) -> &str {
+        "plugin name plus arguments"
+    }
+
+    fn run(
+        &self,
+        _engine_state: &EngineState,
+        _stack: &mut Stack,
+        call: &Call,
+        input: PipelineData,
+    ) -> Result<PipelineData, ShellError> {
+        // Call the command with self path
+        // Decode information from plugin
+        // Create PipelineData
+        let source_file = Path::new(&self.filename);
+        let mut plugin_cmd = create_command(source_file);
+
+        // Both stdout and stdin are piped so we can get the information from the plugin
+        plugin_cmd.stdout(Stdio::piped());
+        plugin_cmd.stdin(Stdio::piped());
+
+        match plugin_cmd.spawn() {
+            Err(err) => Err(ShellError::PluginError(format!("{}", err))),
+            Ok(mut child) => {
+                let input = match input {
+                    PipelineData::Value(value) => value,
+                    PipelineData::Stream(stream) => {
+                        let values = stream.collect::<Vec<Value>>();
+
+                        Value::List {
+                            vals: values,
+                            span: call.head,
+                        }
+                    }
+                };
+
+                // PluginCall information
+                let plugin_call = PluginCall::CallInfo(Box::new(CallInfo {
+                    call: call.clone(),
+                    input,
+                }));
+
+                // Create message to plugin to indicate that signature is required and
+                // send call to plugin asking for signature
+                if let Some(mut stdin_writer) = child.stdin.take() {
+                    plugin_call::encode_call(&plugin_call, &mut stdin_writer)
+                        .map_err(|err| ShellError::PluginError(err.to_string()))?
+                }
+
+                // Deserialize response from plugin to extract the resulting value
+                let signature = if let Some(stdout_reader) = child.stdout.take() {
+                    let mut buf_read = BufReader::with_capacity(OUTPUT_BUFFER_SIZE, stdout_reader);
+                    let response = plugin_call::decode_response(&mut buf_read)
+                        .map_err(|err| ShellError::PluginError(err.to_string()))?;
+
+                    match response {
+                        PluginResponse::Value(value) => {
+                            Ok(PipelineData::Value(value.as_ref().clone()))
+                        }
+                        PluginResponse::Error(msg) => Err(PluginError::DecodingError(msg)),
+                        _ => Err(PluginError::DecodingError(
+                            "result value from plugin not found".into(),
+                        )),
+                    }
+                } else {
+                    Err(PluginError::UnableToGetStdout)
+                }
+                .map_err(|err| ShellError::PluginError(err.to_string()))?;
+
+                match child.wait() {
+                    Err(err) => Err(ShellError::PluginError(format!("{}", err))),
+                    Ok(_) => Ok(signature),
+                }
+            }
+        }
+    }
+
+    fn is_plugin(&self) -> bool {
+        true
+    }
+}
+
+/// The `Plugin` trait defines the API which plugins use to "hook" into nushell.
+pub trait Plugin {
+    fn signature(&self) -> Signature;
+    fn run(&self, call: &Call, input: &Value) -> Result<Value, PluginError>;
+}
+
+// Function used in the plugin definition for the communication protocol between
+// nushell and the external plugin.
+// If you want to create a new plugin you have to use this function as the main
+// entry point for the plugin
+pub fn serve_plugin(plugin: &mut impl Plugin) {
+    let mut stdin_buf = BufReader::with_capacity(OUTPUT_BUFFER_SIZE, std::io::stdin());
+    let plugin_call = decode_call(&mut stdin_buf);
+
+    match plugin_call {
+        Err(err) => {
+            let response = PluginResponse::Error(err.to_string());
+            encode_response(&response, &mut std::io::stdout()).expect("Error encoding response");
+        }
+        Ok(plugin_call) => {
+            match plugin_call {
+                // Sending the signature back to nushell to create the declaration definition
+                PluginCall::Signature => {
+                    let response = PluginResponse::Signature(Box::new(plugin.signature()));
+                    encode_response(&response, &mut std::io::stdout())
+                        .expect("Error encoding response");
+                }
+                PluginCall::CallInfo(call_info) => {
+                    let value = plugin.run(&call_info.call, &call_info.input);
+
+                    let response = match value {
+                        Ok(value) => PluginResponse::Value(Box::new(value)),
+                        Err(err) => PluginResponse::Error(err.to_string()),
+                    };
+                    encode_response(&response, &mut std::io::stdout())
+                        .expect("Error encoding response");
+                }
+            }
+        }
+    }
+}

crates/nu-plugin/src/plugin_call.rs

@@ -81,6 +81,7 @@ pub fn encode_response(
     let mut builder = message.init_root::<plugin_response::Builder>();
 
     match &plugin_response {
+        PluginResponse::Error(msg) => builder.reborrow().set_error(msg.as_str()),
         PluginResponse::Signature(sign) => {
             let signature_builder = builder.reborrow().init_signature();
             signature::serialize_signature(sign, signature_builder)
@@ -105,6 +106,11 @@ pub fn decode_response(reader: &mut impl std::io::BufRead) -> Result<PluginRespo
 
     match reader.which() {
         Err(capnp::NotInSchema(_)) => Err(PluginError::DecodingError("value not in schema".into())),
+        Ok(plugin_response::Error(reader)) => {
+            let msg = reader.map_err(|e| PluginError::DecodingError(e.to_string()))?;
+
+            Ok(PluginResponse::Error(msg.to_string()))
+        }
         Ok(plugin_response::Signature(reader)) => {
             let reader = reader.map_err(|e| PluginError::DecodingError(e.to_string()))?;
             let sign = signature::deserialize_signature(reader)
@@ -253,6 +259,7 @@ mod tests {
             decode_response(&mut buffer.as_slice()).expect("unable to deserialize message");
 
         match returned {
+            PluginResponse::Error(_) => panic!("returned wrong call type"),
             PluginResponse::Value(_) => panic!("returned wrong call type"),
             PluginResponse::Signature(returned_signature) => {
                 assert_eq!(signature.name, returned_signature.name);
@@ -301,10 +308,28 @@ mod tests {
             decode_response(&mut buffer.as_slice()).expect("unable to deserialize message");
 
         match returned {
+            PluginResponse::Error(_) => panic!("returned wrong call type"),
             PluginResponse::Signature(_) => panic!("returned wrong call type"),
             PluginResponse::Value(returned_value) => {
                 assert_eq!(&value, returned_value.as_ref())
             }
         }
     }
+
+    #[test]
+    fn response_round_trip_error() {
+        let message = "some error".to_string();
+        let response = PluginResponse::Error(message.clone());
+
+        let mut buffer: Vec<u8> = Vec::new();
+        encode_response(&response, &mut buffer).expect("unable to serialize message");
+        let returned =
+            decode_response(&mut buffer.as_slice()).expect("unable to deserialize message");
+
+        match returned {
+            PluginResponse::Error(msg) => assert_eq!(message, msg),
+            PluginResponse::Signature(_) => panic!("returned wrong call type"),
+            PluginResponse::Value(_) => panic!("returned wrong call type"),
+        }
+    }
 }

crates/nu-protocol/src/shell_error.rs

@@ -170,13 +170,8 @@ pub enum ShellError {
     #[error("No file to be copied")]
     NoFileToBeCopied(),
 
-    #[error("Unable to serialize message")]
-    #[diagnostic(code(nu::shell::EncodingError), url(docsrs))]
-    EncodingError(String),
-
-    #[error("Unable to read message")]
-    #[diagnostic(code(nu::shell::DecodingError), url(docsrs))]
-    DecodingError(String),
+    #[error("Plugin error")]
+    PluginError(String),
 }
 
 impl From<std::io::Error> for ShellError {