Add test explorer

Cargo.toml

@@ -142,6 +142,7 @@ dashmap = { version = "=5.5.3", features = ["raw-api"] }
 [workspace.lints.rust]
 rust_2018_idioms = "warn"
 unused_lifetimes = "warn"
+unreachable_pub = "warn"
 semicolon_in_expressions_from_macros = "warn"
 
 [workspace.lints.clippy]

crates/flycheck/src/command.rs

@@ -0,0 +1,156 @@
+//! Utilities for running a cargo command like `cargo check` or `cargo test` in a separate thread and
+//! parse its stdout/stderr.
+
+use std::{
+    ffi::OsString,
+    fmt, io,
+    path::PathBuf,
+    process::{ChildStderr, ChildStdout, Command, Stdio},
+};
+
+use command_group::{CommandGroup, GroupChild};
+use crossbeam_channel::{unbounded, Receiver, Sender};
+use stdx::process::streaming_output;
+
+/// Cargo output is structured as a one JSON per line. This trait abstracts parsing one line of
+/// cargo output into a Rust data type.
+pub(crate) trait ParseFromLine: Sized + Send + 'static {
+    fn from_line(line: &str, error: &mut String) -> Option<Self>;
+    fn from_eof() -> Option<Self>;
+}
+
+struct CargoActor<T> {
+    sender: Sender<T>,
+    stdout: ChildStdout,
+    stderr: ChildStderr,
+}
+
+impl<T: ParseFromLine> CargoActor<T> {
+    fn new(sender: Sender<T>, stdout: ChildStdout, stderr: ChildStderr) -> Self {
+        CargoActor { sender, stdout, stderr }
+    }
+
+    fn run(self) -> io::Result<(bool, String)> {
+        // 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 resilient 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
+        // erroneous output.
+
+        let mut stdout_errors = String::new();
+        let mut stderr_errors = String::new();
+        let mut read_at_least_one_stdout_message = false;
+        let mut read_at_least_one_stderr_message = false;
+        let process_line = |line: &str, error: &mut String| {
+            // Try to deserialize a message from Cargo or Rustc.
+            if let Some(t) = T::from_line(line, error) {
+                self.sender.send(t).unwrap();
+                true
+            } else {
+                false
+            }
+        };
+        let output = streaming_output(
+            self.stdout,
+            self.stderr,
+            &mut |line| {
+                if process_line(line, &mut stdout_errors) {
+                    read_at_least_one_stdout_message = true;
+                }
+            },
+            &mut |line| {
+                if process_line(line, &mut stderr_errors) {
+                    read_at_least_one_stderr_message = true;
+                }
+            },
+            &mut || {
+                if let Some(t) = T::from_eof() {
+                    self.sender.send(t).unwrap();
+                }
+            },
+        );
+
+        let read_at_least_one_message =
+            read_at_least_one_stdout_message || read_at_least_one_stderr_message;
+        let mut error = stdout_errors;
+        error.push_str(&stderr_errors);
+        match output {
+            Ok(_) => Ok((read_at_least_one_message, error)),
+            Err(e) => Err(io::Error::new(e.kind(), format!("{e:?}: {error}"))),
+        }
+    }
+}
+
+struct JodGroupChild(GroupChild);
+
+impl Drop for JodGroupChild {
+    fn drop(&mut self) {
+        _ = self.0.kill();
+        _ = self.0.wait();
+    }
+}
+
+/// A handle to a cargo process used for fly-checking.
+pub(crate) struct CommandHandle<T> {
+    /// The handle to the actual cargo process. As we cannot cancel directly from with
+    /// a read syscall dropping and therefore terminating the process is our best option.
+    child: JodGroupChild,
+    thread: stdx::thread::JoinHandle<io::Result<(bool, String)>>,
+    pub(crate) receiver: Receiver<T>,
+    program: OsString,
+    arguments: Vec<OsString>,
+    current_dir: Option<PathBuf>,
+}
+
+impl<T> fmt::Debug for CommandHandle<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("CommandHandle")
+            .field("program", &self.program)
+            .field("arguments", &self.arguments)
+            .field("current_dir", &self.current_dir)
+            .finish()
+    }
+}
+
+impl<T: ParseFromLine> CommandHandle<T> {
+    pub(crate) fn spawn(mut command: Command) -> std::io::Result<Self> {
+        command.stdout(Stdio::piped()).stderr(Stdio::piped()).stdin(Stdio::null());
+        let mut child = command.group_spawn().map(JodGroupChild)?;
+
+        let program = command.get_program().into();
+        let arguments = command.get_args().map(|arg| arg.into()).collect::<Vec<OsString>>();
+        let current_dir = command.get_current_dir().map(|arg| arg.to_path_buf());
+
+        let stdout = child.0.inner().stdout.take().unwrap();
+        let stderr = child.0.inner().stderr.take().unwrap();
+
+        let (sender, receiver) = unbounded();
+        let actor = CargoActor::<T>::new(sender, stdout, stderr);
+        let thread = stdx::thread::Builder::new(stdx::thread::ThreadIntent::Worker)
+            .name("CargoHandle".to_owned())
+            .spawn(move || actor.run())
+            .expect("failed to spawn thread");
+        Ok(CommandHandle { program, arguments, current_dir, child, thread, receiver })
+    }
+
+    pub(crate) fn cancel(mut self) {
+        let _ = self.child.0.kill();
+        let _ = self.child.0.wait();
+    }
+
+    pub(crate) fn join(mut self) -> io::Result<()> {
+        let _ = self.child.0.kill();
+        let exit_status = self.child.0.wait()?;
+        let (read_at_least_one_message, error) = self.thread.join()?;
+        if read_at_least_one_message || exit_status.success() {
+            Ok(())
+        } else {
+            Err(io::Error::new(io::ErrorKind::Other, format!(
+            "Cargo watcher failed, the command produced no valid metadata (exit code: {exit_status:?}):\n{error}"
+        )))
+        }
+    }
+}