Use os_pipe

Cargo.lock

@@ -519,6 +519,16 @@ version = "1.19.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3fdb12b2476b595f9358c5161aa467c2438859caa136dec86c26fdd2efe17b92"
 
+[[package]]
+name = "os_pipe"
+version = "1.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "57119c3b893986491ec9aa85056780d3a0f3cf4da7cc09dd3650dbd6c6738fb9"
+dependencies = [
+ "libc",
+ "windows-sys 0.52.0",
+]
+
 [[package]]
 name = "parking_lot"
 version = "0.12.1"
@@ -677,6 +687,7 @@ dependencies = [
  "crossterm",
  "hashbrown",
  "notify-debouncer-mini",
+ "os_pipe",
  "predicates",
  "ratatui",
  "rustlings-macros",

Cargo.toml

@@ -50,6 +50,7 @@ clap = { version = "4.5.4", features = ["derive"] }
 crossterm = "0.27.0"
 hashbrown = "0.14.3"
 notify-debouncer-mini = "0.4.1"
+os_pipe = "1.1.5"
 ratatui = "0.26.2"
 rustlings-macros = { path = "rustlings-macros", version = "6.0.0-beta.0" }
 serde.workspace = true

src/app_state.rs

@@ -11,7 +11,12 @@ use std::{
     process::{Command, Stdio},
 };
 
-use crate::{embedded::EMBEDDED_FILES, exercise::Exercise, info_file::ExerciseInfo, DEBUG_PROFILE};
+use crate::{
+    embedded::EMBEDDED_FILES,
+    exercise::{Exercise, OUTPUT_CAPACITY},
+    info_file::ExerciseInfo,
+    DEBUG_PROFILE,
+};
 
 const STATE_FILE_NAME: &str = ".rustlings-state.txt";
 const BAD_INDEX_ERR: &str = "The current exercise index is higher than the number of exercises";
@@ -302,11 +307,13 @@ impl AppState {
         let Some(ind) = self.next_pending_exercise_ind() else {
             writer.write_all(RERUNNING_ALL_EXERCISES_MSG)?;
 
+            let mut output = Vec::with_capacity(OUTPUT_CAPACITY);
             for (exercise_ind, exercise) in self.exercises().iter().enumerate() {
                 writer.write_fmt(format_args!("Running {exercise} ... "))?;
                 writer.flush()?;
 
-                if !exercise.run()?.status.success() {
+                let success = exercise.run(&mut output)?;
+                if !success {
                     writer.write_fmt(format_args!("{}\n\n", "FAILED".red()))?;
 
                     self.current_exercise_ind = exercise_ind;
@@ -322,6 +329,8 @@ impl AppState {
                 }
 
                 writer.write_fmt(format_args!("{}\n", "ok".green()))?;
+
+                output.clear();
             }
 
             writer.execute(Clear(ClearType::All))?;

src/exercise.rs

@@ -2,11 +2,42 @@ use anyhow::{Context, Result};
 use crossterm::style::{style, StyledContent, Stylize};
 use std::{
     fmt::{self, Display, Formatter},
-    path::Path,
-    process::{Command, Output},
+    io::{Read, Write},
+    process::Command,
 };
 
-use crate::{info_file::Mode, terminal_link::TerminalFileLink, DEBUG_PROFILE};
+use crate::{in_official_repo, info_file::Mode, terminal_link::TerminalFileLink, DEBUG_PROFILE};
+
+// TODO
+pub const OUTPUT_CAPACITY: usize = 1 << 12;
+
+fn run_command(mut cmd: Command, cmd_description: &str, output: &mut Vec<u8>) -> Result<bool> {
+    let (mut reader, writer) = os_pipe::pipe().with_context(|| {
+        format!("Failed to create a pipe to run the command `{cmd_description}``")
+    })?;
+
+    let mut handle = cmd
+        .stdout(writer.try_clone().with_context(|| {
+            format!("Failed to clone the pipe writer for the command `{cmd_description}`")
+        })?)
+        .stderr(writer)
+        .spawn()
+        .with_context(|| format!("Failed to run the command `{cmd_description}`"))?;
+
+    // Prevent pipe deadlock.
+    drop(cmd);
+
+    reader
+        .read_to_end(output)
+        .with_context(|| format!("Failed to read the output of the command `{cmd_description}`"))?;
+
+    output.push(b'\n');
+
+    handle
+        .wait()
+        .with_context(|| format!("Failed to wait on the command `{cmd_description}` to exit"))
+        .map(|status| status.success())
+}
 
 pub struct Exercise {
     pub dir: Option<&'static str>,
@@ -22,13 +53,30 @@ pub struct Exercise {
 }
 
 impl Exercise {
-    fn cargo_cmd(&self, command: &str, args: &[&str]) -> Result<Output> {
+    fn run_bin(&self, output: &mut Vec<u8>) -> Result<bool> {
+        writeln!(output, "{}", "Output".bold().magenta().underlined())?;
+
+        let bin_path = format!("target/debug/{}", self.name);
+        run_command(Command::new(&bin_path), &bin_path, output)
+    }
+
+    fn cargo_cmd(
+        &self,
+        command: &str,
+        args: &[&str],
+        cmd_description: &str,
+        output: &mut Vec<u8>,
+        dev: bool,
+    ) -> Result<bool> {
         let mut cmd = Command::new("cargo");
         cmd.arg(command);
 
         // A hack to make `cargo run` work when developing Rustlings.
-        if DEBUG_PROFILE && Path::new("tests").exists() {
-            cmd.arg("--manifest-path").arg("dev/Cargo.toml");
+        if dev {
+            cmd.arg("--manifest-path")
+                .arg("dev/Cargo.toml")
+                .arg("--target-dir")
+                .arg("target");
         }
 
         cmd.arg("--color")
@@ -36,15 +84,43 @@ impl Exercise {
             .arg("-q")
             .arg("--bin")
             .arg(self.name)
-            .args(args)
-            .output()
-            .context("Failed to run Cargo")
+            .args(args);
+
+        run_command(cmd, cmd_description, output)
+    }
+
+    fn cargo_cmd_with_bin_output(
+        &self,
+        command: &str,
+        args: &[&str],
+        cmd_description: &str,
+        output: &mut Vec<u8>,
+        dev: bool,
+    ) -> Result<bool> {
+        // Discard the output of `cargo build` because it will be shown again by the Cargo command.
+        output.clear();
+
+        let cargo_cmd_success = self.cargo_cmd(command, args, cmd_description, output, dev)?;
+
+        let run_success = self.run_bin(output)?;
+
+        Ok(cargo_cmd_success && run_success)
     }
 
-    pub fn run(&self) -> Result<Output> {
+    pub fn run(&self, output: &mut Vec<u8>) -> Result<bool> {
+        output.clear();
+
+        // Developing the official Rustlings.
+        let dev = DEBUG_PROFILE && in_official_repo();
+
+        let build_success = self.cargo_cmd("build", &[], "cargo build …", output, dev)?;
+        if !build_success {
+            return Ok(false);
+        }
+
         match self.mode {
-            Mode::Run => self.cargo_cmd("run", &[]),
-            Mode::Test => self.cargo_cmd(
+            Mode::Run => self.run_bin(output),
+            Mode::Test => self.cargo_cmd_with_bin_output(
                 "test",
                 &[
                     "--",
@@ -54,10 +130,16 @@ impl Exercise {
                     "--format",
                     "pretty",
                 ],
+                "cargo test …",
+                output,
+                dev,
             ),
-            Mode::Clippy => self.cargo_cmd(
+            Mode::Clippy => self.cargo_cmd_with_bin_output(
                 "clippy",
-                &["--", "-D", "warnings", "-D", "clippy::float_cmp"],
+                &["--", "-D", "warnings"],
+                "cargo clippy …",
+                output,
+                dev,
             ),
         }
     }

src/main.rs

@@ -75,10 +75,14 @@ enum Subcommands {
     Dev(DevCommands),
 }
 
+fn in_official_repo() -> bool {
+    Path::new("dev/rustlings-repo.txt").exists()
+}
+
 fn main() -> Result<()> {
     let args = Args::parse();
 
-    if !DEBUG_PROFILE && Path::new("dev/rustlings-repo.txt").exists() {
+    if !DEBUG_PROFILE && in_official_repo() {
         bail!("{OLD_METHOD_ERR}");
     }
 

src/run.rs

@@ -4,20 +4,19 @@ use std::io::{self, Write};
 
 use crate::{
     app_state::{AppState, ExercisesProgress},
+    exercise::OUTPUT_CAPACITY,
     terminal_link::TerminalFileLink,
 };
 
 pub fn run(app_state: &mut AppState) -> Result<()> {
     let exercise = app_state.current_exercise();
-    let output = exercise.run()?;
+    let mut output = Vec::with_capacity(OUTPUT_CAPACITY);
+    let success = exercise.run(&mut output)?;
 
     let mut stdout = io::stdout().lock();
-    stdout.write_all(&output.stdout)?;
-    stdout.write_all(b"\n")?;
-    stdout.write_all(&output.stderr)?;
-    stdout.flush()?;
+    stdout.write_all(&output)?;
 
-    if !output.status.success() {
+    if !success {
         app_state.set_pending(app_state.current_exercise_ind())?;
 
         bail!(

src/watch/state.rs

@@ -8,6 +8,7 @@ use std::io::{self, StdoutLock, Write};
 
 use crate::{
     app_state::{AppState, ExercisesProgress},
+    exercise::OUTPUT_CAPACITY,
     progress_bar::progress_bar,
     terminal_link::TerminalFileLink,
 };
@@ -21,8 +22,7 @@ enum DoneStatus {
 pub struct WatchState<'a> {
     writer: StdoutLock<'a>,
     app_state: &'a mut AppState,
-    stdout: Option<Vec<u8>>,
-    stderr: Option<Vec<u8>>,
+    output: Vec<u8>,
     show_hint: bool,
     done_status: DoneStatus,
     manual_run: bool,
@@ -35,8 +35,7 @@ impl<'a> WatchState<'a> {
         Self {
             writer,
             app_state,
-            stdout: None,
-            stderr: None,
+            output: Vec::with_capacity(OUTPUT_CAPACITY),
             show_hint: false,
             done_status: DoneStatus::Pending,
             manual_run,
@@ -51,11 +50,8 @@ impl<'a> WatchState<'a> {
     pub fn run_current_exercise(&mut self) -> Result<()> {
         self.show_hint = false;
 
-        let output = self.app_state.current_exercise().run()?;
-        self.stdout = Some(output.stdout);
-
-        if output.status.success() {
-            self.stderr = None;
+        let success = self.app_state.current_exercise().run(&mut self.output)?;
+        if success {
             self.done_status =
                 if let Some(solution_path) = self.app_state.current_solution_path()? {
                     DoneStatus::DoneWithSolution(solution_path)
@@ -66,7 +62,6 @@ impl<'a> WatchState<'a> {
             self.app_state
                 .set_pending(self.app_state.current_exercise_ind())?;
 
-            self.stderr = Some(output.stderr);
             self.done_status = DoneStatus::Pending;
         }
 
@@ -116,16 +111,7 @@ impl<'a> WatchState<'a> {
 
         self.writer.execute(Clear(ClearType::All))?;
 
-        if let Some(stdout) = &self.stdout {
-            self.writer.write_all(stdout)?;
-            self.writer.write_all(b"\n")?;
-        }
-
-        if let Some(stderr) = &self.stderr {
-            self.writer.write_all(stderr)?;
-            self.writer.write_all(b"\n")?;
-        }
-
+        self.writer.write_all(&self.output)?;
         self.writer.write_all(b"\n")?;
 
         if self.show_hint {