1 files changed, 359 insertions, 0 deletions

diff --git a/crates/ra_flycheck/src/lib.rs b/crates/ra_flycheck/src/lib.rs
new file mode 100644
index 000000000..75aece45f
--- /dev/null
+++ b/crates/ra_flycheck/src/lib.rs
@@ -0,0 +1,359 @@
+//! cargo_check provides the functionality needed to run `cargo check` or
+//! another compatible command (f.x. clippy) in a background thread and provide
+//! LSP diagnostics based on the output of the command.
+mod conv;
+
+use std::{
+    error, fmt,
+    io::{BufRead, BufReader},
+    path::{Path, PathBuf},
+    process::{Command, Stdio},
+    time::Instant,
+};
+
+use cargo_metadata::Message;
+use crossbeam_channel::{never, select, unbounded, Receiver, RecvError, Sender};
+use lsp_types::{
+    CodeAction, CodeActionOrCommand, Diagnostic, Url, WorkDoneProgress, WorkDoneProgressBegin,
+    WorkDoneProgressEnd, WorkDoneProgressReport,
+};
+
+use crate::conv::{map_rust_diagnostic_to_lsp, MappedRustDiagnostic};
+
+pub use crate::conv::url_from_path_with_drive_lowercasing;
+
+#[derive(Clone, Debug)]
+pub struct CheckConfig {
+    pub args: Vec<String>,
+    pub command: String,
+    pub all_targets: bool,
+}
+
+/// Flycheck wraps the shared state and communication machinery used for
+/// running `cargo check` (or other compatible command) and providing
+/// diagnostics based on the output.
+/// The spawned thread is shut down when this struct is dropped.
+#[derive(Debug)]
+pub struct Flycheck {
+    // XXX: drop order is significant
+    cmd_send: Sender<CheckCommand>,
+    handle: jod_thread::JoinHandle<()>,
+    pub task_recv: Receiver<CheckTask>,
+}
+
+impl Flycheck {
+    pub fn new(config: CheckConfig, workspace_root: PathBuf) -> Flycheck {
+        let (task_send, task_recv) = unbounded::<CheckTask>();
+        let (cmd_send, cmd_recv) = unbounded::<CheckCommand>();
+        let handle = jod_thread::spawn(move || {
+            let mut check = FlycheckThread::new(config, workspace_root);
+            check.run(&task_send, &cmd_recv);
+        });
+        Flycheck { task_recv, cmd_send, handle }
+    }
+
+    /// Schedule a re-start of the cargo check worker.
+    pub fn update(&self) {
+        self.cmd_send.send(CheckCommand::Update).unwrap();
+    }
+}
+
+#[derive(Debug)]
+pub enum CheckTask {
+    /// Request a clearing of all cached diagnostics from the check watcher
+    ClearDiagnostics,
+
+    /// Request adding a diagnostic with fixes included to a file
+    AddDiagnostic { url: Url, diagnostic: Diagnostic, fixes: Vec<CodeActionOrCommand> },
+
+    /// Request check progress notification to client
+    Status(WorkDoneProgress),
+}
+
+pub enum CheckCommand {
+    /// Request re-start of check thread
+    Update,
+}
+
+struct FlycheckThread {
+    options: CheckConfig,
+    workspace_root: PathBuf,
+    last_update_req: Option<Instant>,
+    // XXX: drop order is significant
+    message_recv: Receiver<CheckEvent>,
+    /// WatchThread exists to wrap around the communication needed to be able to
+    /// run `cargo check` without blocking. Currently the Rust standard library
+    /// doesn't provide a way to read sub-process output without blocking, so we
+    /// have to wrap sub-processes output handling in a thread and pass messages
+    /// back over a channel.
+    check_process: Option<jod_thread::JoinHandle<()>>,
+}
+
+impl FlycheckThread {
+    fn new(options: CheckConfig, workspace_root: PathBuf) -> FlycheckThread {
+        FlycheckThread {
+            options,
+            workspace_root,
+            last_update_req: None,
+            message_recv: never(),
+            check_process: None,
+        }
+    }
+
+    fn run(&mut self, task_send: &Sender<CheckTask>, cmd_recv: &Receiver<CheckCommand>) {
+        // If we rerun the thread, we need to discard the previous check results first
+        self.clean_previous_results(task_send);
+
+        loop {
+            select! {
+                recv(&cmd_recv) -> cmd => match cmd {
+                    Ok(cmd) => self.handle_command(cmd),
+                    Err(RecvError) => {
+                        // Command channel has closed, so shut down
+                        break;
+                    },
+                },
+                recv(self.message_recv) -> msg => match msg {
+                    Ok(msg) => self.handle_message(msg, task_send),
+                    Err(RecvError) => {
+                        // Watcher finished, replace it with a never channel to
+                        // avoid busy-waiting.
+                        self.message_recv = never();
+                        self.check_process = None;
+                    },
+                }
+            };
+
+            if self.should_recheck() {
+                self.last_update_req = None;
+                task_send.send(CheckTask::ClearDiagnostics).unwrap();
+                self.restart_check_process();
+            }
+        }
+    }
+
+    fn clean_previous_results(&self, task_send: &Sender<CheckTask>) {
+        task_send.send(CheckTask::ClearDiagnostics).unwrap();
+        task_send
+            .send(CheckTask::Status(WorkDoneProgress::End(WorkDoneProgressEnd { message: None })))
+            .unwrap();
+    }
+
+    fn should_recheck(&mut self) -> bool {
+        if let Some(_last_update_req) = &self.last_update_req {
+            // We currently only request an update on save, as we need up to
+            // date source on disk for cargo check to do it's magic, so we
+            // don't really need to debounce the requests at this point.
+            return true;
+        }
+        false
+    }
+
+    fn handle_command(&mut self, cmd: CheckCommand) {
+        match cmd {
+            CheckCommand::Update => self.last_update_req = Some(Instant::now()),
+        }
+    }
+
+    fn handle_message(&self, msg: CheckEvent, task_send: &Sender<CheckTask>) {
+        match msg {
+            CheckEvent::Begin => {
+                task_send
+                    .send(CheckTask::Status(WorkDoneProgress::Begin(WorkDoneProgressBegin {
+                        title: "Running 'cargo check'".to_string(),
+                        cancellable: Some(false),
+                        message: None,
+                        percentage: None,
+                    })))
+                    .unwrap();
+            }
+
+            CheckEvent::End => {
+                task_send
+                    .send(CheckTask::Status(WorkDoneProgress::End(WorkDoneProgressEnd {
+                        message: None,
+                    })))
+                    .unwrap();
+            }
+
+            CheckEvent::Msg(Message::CompilerArtifact(msg)) => {
+                task_send
+                    .send(CheckTask::Status(WorkDoneProgress::Report(WorkDoneProgressReport {
+                        cancellable: Some(false),
+                        message: Some(msg.target.name),
+                        percentage: None,
+                    })))
+                    .unwrap();
+            }
+
+            CheckEvent::Msg(Message::CompilerMessage(msg)) => {
+                let map_result = map_rust_diagnostic_to_lsp(&msg.message, &self.workspace_root);
+                if map_result.is_empty() {
+                    return;
+                }
+
+                for MappedRustDiagnostic { location, diagnostic, fixes } in map_result {
+                    let fixes = fixes
+                        .into_iter()
+                        .map(|fix| {
+                            CodeAction { diagnostics: Some(vec![diagnostic.clone()]), ..fix }.into()
+                        })
+                        .collect();
+
+                    task_send
+                        .send(CheckTask::AddDiagnostic { url: location.uri, diagnostic, fixes })
+                        .unwrap();
+                }
+            }
+
+            CheckEvent::Msg(Message::BuildScriptExecuted(_msg)) => {}
+            CheckEvent::Msg(Message::Unknown) => {}
+        }
+    }
+
+    fn restart_check_process(&mut self) {
+        // First, clear and cancel the old thread
+        self.message_recv = never();
+        self.check_process = None;
+
+        let mut args: Vec<String> = vec![
+            self.options.command.clone(),
+            "--workspace".to_string(),
+            "--message-format=json".to_string(),
+            "--manifest-path".to_string(),
+            format!("{}/Cargo.toml", self.workspace_root.display()),
+        ];
+        if self.options.all_targets {
+            args.push("--all-targets".to_string());
+        }
+        args.extend(self.options.args.iter().cloned());
+
+        let (message_send, message_recv) = unbounded();
+        let workspace_root = self.workspace_root.to_owned();
+        self.message_recv = message_recv;
+        self.check_process = Some(jod_thread::spawn(move || {
+            // If we trigger an error here, we will do so in the loop instead,
+            // which will break out of the loop, and continue the shutdown
+            let _ = message_send.send(CheckEvent::Begin);
+
+            let res = run_cargo(&args, Some(&workspace_root), &mut |message| {
+                // Skip certain kinds of messages to only spend time on what's useful
+                match &message {
+                    Message::CompilerArtifact(artifact) if artifact.fresh => return true,
+                    Message::BuildScriptExecuted(_) => return true,
+                    Message::Unknown => return true,
+                    _ => {}
+                }
+
+                // if the send channel was closed, we want to shutdown
+                message_send.send(CheckEvent::Msg(message)).is_ok()
+            });
+
+            if let Err(err) = res {
+                // FIXME: make the `message_send` to be `Sender<Result<CheckEvent, CargoError>>`
+                // to display user-caused misconfiguration errors instead of just logging them here
+                log::error!("Cargo watcher failed {:?}", err);
+            }
+
+            // We can ignore any error here, as we are already in the progress
+            // of shutting down.
+            let _ = message_send.send(CheckEvent::End);
+        }))
+    }
+}
+
+#[derive(Debug)]
+pub struct DiagnosticWithFixes {
+    diagnostic: Diagnostic,
+    fixes: Vec<CodeAction>,
+}
+
+enum CheckEvent {
+    Begin,
+    Msg(cargo_metadata::Message),
+    End,
+}
+
+#[derive(Debug)]
+pub struct CargoError(String);
+
+impl fmt::Display for CargoError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "Cargo failed: {}", self.0)
+    }
+}
+impl error::Error for CargoError {}
+
+fn run_cargo(
+    args: &[String],
+    current_dir: Option<&Path>,
+    on_message: &mut dyn FnMut(cargo_metadata::Message) -> bool,
+) -> Result<(), CargoError> {
+    let mut command = Command::new("cargo");
+    if let Some(current_dir) = current_dir {
+        command.current_dir(current_dir);
+    }
+
+    let mut child = command
+        .args(args)
+        .stdout(Stdio::piped())
+        .stderr(Stdio::null())
+        .stdin(Stdio::null())
+        .spawn()
+        .expect("couldn't launch cargo");
+
+    // We manually read a line at a time, instead of using serde's
+    // stream deserializers, because the deserializer cannot recover
+    // from an error, resulting in it getting stuck, because we try to
+    // be resillient against failures.
+    //
+    // Because cargo only outputs one JSON object per line, we can
+    // simply skip a line if it doesn't parse, which just ignores any
+    // erroneus output.
+    let stdout = BufReader::new(child.stdout.take().unwrap());
+    let mut read_at_least_one_message = false;
+
+    for line in stdout.lines() {
+        let line = match line {
+            Ok(line) => line,
+            Err(err) => {
+                log::error!("Couldn't read line from cargo: {}", err);
+                continue;
+            }
+        };
+
+        let message = serde_json::from_str::<cargo_metadata::Message>(&line);
+        let message = match message {
+            Ok(message) => message,
+            Err(err) => {
+                log::error!("Invalid json from cargo check, ignoring ({}): {:?} ", err, line);
+                continue;
+            }
+        };
+
+        read_at_least_one_message = true;
+
+        if !on_message(message) {
+            break;
+        }
+    }
+
+    // It is okay to ignore the result, as it only errors if the process is already dead
+    let _ = child.kill();
+
+    let err_msg = match child.wait() {
+        Ok(exit_code) if !exit_code.success() && !read_at_least_one_message => {
+            // FIXME: Read the stderr to display the reason, see `read2()` reference in PR comment:
+            // https://github.com/rust-analyzer/rust-analyzer/pull/3632#discussion_r395605298
+            format!(
+                "the command produced no valid metadata (exit code: {:?}): cargo {}",
+                exit_code,
+                args.join(" ")
+            )
+        }
+        Err(err) => format!("io error: {:?}", err),
+        Ok(_) => return Ok(()),
+    };
+
+    Err(CargoError(err_msg))
+}