first

src/log.rs

@@ -0,0 +1,35 @@
+//! Tiny stderr logger. We use a consistent `==> <action>: <details>` prefix
+//! so progress messages are easy to scan during long builds.
+
+use std::io::{IsTerminal, Write};
+
+const ARROW: &str = "==>";
+
+fn paint(color: &str, text: &str) -> String {
+    if std::io::stderr().is_terminal() {
+        format!("\x1b[{color}m{text}\x1b[0m")
+    } else {
+        text.to_owned()
+    }
+}
+
+fn emit(color: &str, action: &str, details: &str) {
+    let arrow = paint(color, ARROW);
+    let action = paint("1", action);
+    let _ = writeln!(std::io::stderr(), "{arrow} {action} {details}");
+}
+
+/// Major step, e.g. starting a build or packaging an output.
+pub fn step(action: &str, details: &str) {
+    emit("1;34", action, details); // bold blue
+}
+
+/// Cache hit / skipped work.
+pub fn skip(action: &str, details: &str) {
+    emit("1;33", action, details); // bold yellow
+}
+
+/// Sub-step inside a larger action.
+pub fn info(action: &str, details: &str) {
+    emit("1;32", action, details); // bold green
+}