Make cargo run work

src/bin/gen-dev-cargo-toml.rs

@@ -0,0 +1,56 @@
+use anyhow::{bail, Context, Result};
+use serde::Deserialize;
+use std::{
+    fs::{self, create_dir},
+    io::ErrorKind,
+};
+
+#[derive(Deserialize)]
+struct Exercise {
+    name: String,
+    path: String,
+}
+
+#[derive(Deserialize)]
+struct InfoToml {
+    exercises: Vec<Exercise>,
+}
+
+fn main() -> Result<()> {
+    let exercises = toml_edit::de::from_str::<InfoToml>(
+        &fs::read_to_string("info.toml").context("Failed to read `info.toml`")?,
+    )
+    .context("Failed to deserialize `info.toml`")?
+    .exercises;
+
+    let mut buf = Vec::with_capacity(1 << 14);
+
+    buf.extend_from_slice(b"bin = [\n");
+
+    for exercise in exercises {
+        buf.extend_from_slice(b"  { name = \"");
+        buf.extend_from_slice(exercise.name.as_bytes());
+        buf.extend_from_slice(b"\", path = \"../");
+        buf.extend_from_slice(exercise.path.as_bytes());
+        buf.extend_from_slice(b"\" },\n");
+    }
+
+    buf.extend_from_slice(
+        br#"]
+
+[package]
+name = "rustlings"
+version = "0.0.0"
+edition = "2021"
+publish = false
+"#,
+    );
+
+    if let Err(e) = create_dir("dev") {
+        if e.kind() != ErrorKind::AlreadyExists {
+            bail!("Failed to create the `dev` directory: {e}");
+        }
+    }
+
+    fs::write("dev/Cargo.toml", buf).context("Failed to write `dev/Cargo.toml`")
+}

src/exercise.rs

@@ -91,9 +91,17 @@ pub struct ContextLine {
 
 impl Exercise {
     fn cargo_cmd(&self, command: &str, args: &[&str]) -> Result<Output> {
-        Command::new("cargo")
-            .arg(command)
-            .arg("--color")
+        let mut cmd = Command::new("cargo");
+        cmd.arg(command);
+
+        // A hack to make `cargo run` work when developing Rustlings.
+        // Use `dev/Cargo.toml` when in the directory of the repository.
+        #[cfg(debug_assertions)]
+        if std::path::Path::new("tests").exists() {
+            cmd.arg("--manifest-path").arg("dev/Cargo.toml");
+        }
+
+        cmd.arg("--color")
             .arg("always")
             .arg("-q")
             .arg("--bin")