Improve error handling to work well in CI.

xtask/src/main.rs

@@ -2,19 +2,6 @@ use std::{env, process::Command};
 
 type DynError = Box<dyn std::error::Error>;
 
-const INSTALLATION_ARGS: [[&str; 4]; 7] = [
-    // The --locked flag is important for reproducible builds. It also
-    // avoids breakage due to skews between mdbook and mdbook-svgbob.
-    ["mdbook", "--locked", "--version", "0.4.44"],
-    ["mdbook-svgbob", "--locked", "--version", "0.2.1"],
-    ["mdbook-pandoc", "--locked", "--version", "0.9.3"],
-    ["mdbook-i18n-helpers", "--locked", "--version", "0.3.5"],
-    ["i18n-report", "--locked", "--version", "0.2.0"],
-    // These packages are located in this repository
-    ["--path", "mdbook-exerciser", "--locked", ""],
-    ["--path", "mdbook-course", "--locked", ""],
-];
-
 fn main() {
     if let Err(e) = execute_task() {
         eprintln!("{e}");
@@ -26,35 +13,59 @@ fn execute_task() -> Result<(), DynError> {
     let task = env::args().nth(1);
     match task.as_deref() {
         Some("install-tools") => install_tools()?,
-        _ => print_help(task.as_deref()),
+        _ => {
+            return Err(Box::from(get_help_string(task.as_deref())));
+        }
     }
     Ok(())
 }
 
 fn install_tools() -> Result<(), DynError> {
     println!("Installing project tools...");
 
-    for args in INSTALLATION_ARGS.iter() {
-        Command::new(env!("CARGO"))
+    let install_args: Vec<Vec<&str>> = vec![
+        // The --locked flag is important for reproducible builds. It also
+        // avoids breakage due to skews between mdbook and mdbook-svgbob.
+        vec!["mdbook", "--locked", "--version", "0.4.44"],
+        vec!["mdbook-svgbob", "--locked", "--version", "0.2.1"],
+        vec!["mdbook-pandoc", "--locked", "--version", "0.9.3"],
+        vec!["mdbook-i18n-helpers", "--locked", "--version", "0.3.5"],
+        vec!["i18n-report", "--locked", "--version", "0.2.0"],
+        // These packages are located in this repository
+        vec!["--path", "mdbook-exerciser", "--locked"],
+        vec!["--path", "mdbook-course", "--locked"],
+    ];
+
+    for args in &install_args {
+        let status = Command::new(env!("CARGO"))
             .arg("install")
-            .args(args.iter().filter(|a| **a != ""))
-            .status()?;
+            .args(args)
+            .status()
+            .expect("Failed to execute cargo install");
+
+        if !status.success() {
+            let error_message = format!(
+                "cargo install {} {} exited with status code: {}",
+                args.get(0).unwrap(),
+                args.get(1).unwrap(),
+                status.code().unwrap()
+            );
+            return Err(Box::from(error_message));
+        }
     }
 
     Ok(())
 }
 
-fn print_help(task: Option<&str>) {
+fn get_help_string(task: Option<&str>) -> String {
     if let Some(t) = task {
-        eprintln!(
+        format!(
             "Unrecognized task '{t}'. Available tasks:
 
 install-tools            Installs the tools the project depends on.
-
-Run with `cargo xtask [task]`.
 "
-        );
+        )
     } else {
-        eprintln!("Missing task. To execute a task run `cargo xtask [task]`.");
+        "Missing task. To execute a task run `cargo xtask [task]`.".to_string()
     }
 }