1 files changed, 93 insertions, 0 deletions
diff --git a/src/cmd.rs b/src/cmd.rs
new file mode 100644
index 0000000..6092f53
--- /dev/null
+++ b/src/cmd.rs
@@ -0,0 +1,93 @@
+use anyhow::{Context, Result};
+use std::{io::Read, path::Path, process::Command};
+
+/// Run a command with a description for a possible error and append the merged stdout and stderr.
+/// The boolean in the returned `Result` is true if the command's exit status is success.
+pub fn run_cmd(mut cmd: Command, 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 `{description}``"))?;
+
+    let writer_clone = writer.try_clone().with_context(|| {
+        format!("Failed to clone the pipe writer for the command `{description}`")
+    })?;
+
+    let mut handle = cmd
+        .stdout(writer_clone)
+        .stderr(writer)
+        .spawn()
+        .with_context(|| format!("Failed to run the command `{description}`"))?;
+
+    // Prevent pipe deadlock.
+    drop(cmd);
+
+    reader
+        .read_to_end(output)
+        .with_context(|| format!("Failed to read the output of the command `{description}`"))?;
+
+    output.push(b'\n');
+
+    handle
+        .wait()
+        .with_context(|| format!("Failed to wait on the command `{description}` to exit"))
+        .map(|status| status.success())
+}
+
+pub struct CargoCmd<'a> {
+    pub subcommand: &'a str,
+    pub args: &'a [&'a str],
+    pub bin_name: &'a str,
+    pub description: &'a str,
+    /// RUSTFLAGS="-A warnings"
+    pub hide_warnings: bool,
+    /// Added as `--target-dir` if `Self::dev` is true.
+    pub target_dir: &'a Path,
+    /// The output buffer to append the merged stdout and stderr.
+    pub output: &'a mut Vec<u8>,
+    /// true while developing Rustlings.
+    pub dev: bool,
+}
+
+impl<'a> CargoCmd<'a> {
+    /// Run `cargo SUBCOMMAND --bin EXERCISE_NAME … ARGS`.
+    pub fn run(&mut self) -> Result<bool> {
+        let mut cmd = Command::new("cargo");
+        cmd.arg(self.subcommand);
+
+        // A hack to make `cargo run` work when developing Rustlings.
+        if self.dev {
+            cmd.arg("--manifest-path")
+                .arg("dev/Cargo.toml")
+                .arg("--target-dir")
+                .arg(self.target_dir);
+        }
+
+        cmd.arg("--color")
+            .arg("always")
+            .arg("-q")
+            .arg("--bin")
+            .arg(self.bin_name)
+            .args(self.args);
+
+        if self.hide_warnings {
+            cmd.env("RUSTFLAGS", "-A warnings");
+        }
+
+        run_cmd(cmd, self.description, self.output)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_run_cmd() {
+        let mut cmd = Command::new("echo");
+        cmd.arg("Hello");
+
+        let mut output = Vec::with_capacity(8);
+        run_cmd(cmd, "echo …", &mut output).unwrap();
+
+        assert_eq!(output, b"Hello\n\n");
+    }
+}