Improve error output of wasm-builder when wasm ins't installed

utils/wasm-builder/Cargo.toml

@@ -22,3 +22,4 @@ fs2 = "0.4.3"
 wasm-gc-api = "0.1.11"
 atty = "0.2.13"
 itertools = "0.8.2"
+ansi_term = "0.12.1"

utils/wasm-builder/src/lib.rs

@@ -179,7 +179,7 @@ pub fn build_project_with_default_rustflags(
 			bloaty.wasm_binary_bloaty_path_escaped(),
 		)
 	};
-	
+
 	write_file_if_changed(
 			file_name.into(),
 			format!(
@@ -309,3 +309,8 @@ impl CargoCommand {
 				.contains("-nightly")
 	}
 }
+
+/// Returns `true` when color output is enabled.
+fn color_output_enabled() -> bool {
+	env::var(crate::WASM_BUILD_NO_COLOR).is_err()
+}

utils/wasm-builder/src/prerequisites.rs

@@ -18,14 +18,24 @@
 use std::fs;
 
 use tempfile::tempdir;
+use ansi_term::Color;
+
+/// Print an error message.
+fn print_error_message(message: &str) -> String {
+	if super::color_output_enabled() {
+		Color::Red.bold().paint(message).to_string()
+	} else {
+		message.into()
+	}
+}
 
 /// Checks that all prerequisites are installed.
 ///
 /// # Returns
 /// Returns `None` if everything was found and `Some(ERR_MSG)` if something could not be found.
-pub fn check() -> Option<&'static str> {
+pub fn check() -> Option<String> {
 	if !check_nightly_installed(){
-		return Some("Rust nightly not installed, please install it!")
+		return Some(print_error_message("Rust nightly not installed, please install it!"))
 	}
 
 	check_wasm_toolchain_installed()
@@ -35,7 +45,7 @@ fn check_nightly_installed() -> bool {
 	crate::get_nightly_cargo().is_nightly()
 }
 
-fn check_wasm_toolchain_installed() -> Option<&'static str> {
+fn check_wasm_toolchain_installed() -> Option<String> {
 	let temp = tempdir().expect("Creating temp dir does not fail; qed");
 	fs::create_dir_all(temp.path().join("src")).expect("Creating src dir does not fail; qed");
 
@@ -59,22 +69,39 @@ fn check_wasm_toolchain_installed() -> Option<&'static str> {
 	fs::write(&test_file, "pub fn test() {}")
 		.expect("Writing to the test file does not fail; qed");
 
-	let err_msg = "Rust WASM toolchain not installed, please install it!";
+	let err_msg = print_error_message("Rust WASM toolchain not installed, please install it!");
 	let manifest_path = manifest_path.display().to_string();
-	crate::get_nightly_cargo()
-		.command()
-		.args(&["build", "--target=wasm32-unknown-unknown", "--manifest-path", &manifest_path])
+
+	let mut build_cmd = crate::get_nightly_cargo().command();
+
+	build_cmd.args(&["build", "--target=wasm32-unknown-unknown", "--manifest-path", &manifest_path]);
+
+	if super::color_output_enabled() {
+		build_cmd.arg("--color=always");
+	}
+
+	build_cmd
 		.output()
-		.map_err(|_| err_msg)
+		.map_err(|_| err_msg.clone())
 		.and_then(|s|
 			if s.status.success() {
 				Ok(())
 			} else {
 				match String::from_utf8(s.stderr) {
 					Ok(ref err) if err.contains("linker `rust-lld` not found") => {
-						Err("`rust-lld` not found, please install it!")
+						Err(print_error_message("`rust-lld` not found, please install it!"))
 					},
-					_ => Err(err_msg)
+					Ok(ref err) => Err(
+						format!(
+							"{}\n\n{}\n{}\n{}{}\n",
+							err_msg,
+							Color::Yellow.bold().paint("Further error information:"),
+							Color::Yellow.bold().paint("-".repeat(60)),
+							err,
+							Color::Yellow.bold().paint("-".repeat(60)),
+						)
+					),
+					Err(_) => Err(err_msg),
 				}
 			}
 		)

utils/wasm-builder/src/wasm_project.rs

@@ -449,7 +449,7 @@ fn build_project(project: &Path, default_rustflags: &str) {
 		// We don't want to call ourselves recursively
 		.env(crate::SKIP_BUILD_ENV, "");
 
-	if env::var(crate::WASM_BUILD_NO_COLOR).is_err() {
+	if super::color_output_enabled() {
 		build_cmd.arg("--color=always");
 	}