Show indicators that perf script is running

Perf script can take a long time to run. This change adds an indicator
to show that it is running so that the user knows that their application
is not causing the terminal to hang.

Addresses flamegraph-rs#270

Cargo.toml

@@ -23,8 +23,10 @@ anyhow = "1.0.43"
 cargo_metadata = "0.18"
 clap = { version = "4.0.11", features = ["derive"] }
 clap_complete = "4.0.2"
+indicatif = "0.17.8"
 inferno = { version = "0.11.0", default_features = false, features = ["multithreaded", "nameattr"] }
 opener = "0.7.1"
+scopeguard = "1.2.0"
 shlex = "1.1.0"
 
 [target.'cfg(unix)'.dependencies]

src/lib.rs

@@ -34,6 +34,10 @@ pub enum Workload {
 
 #[cfg(target_os = "linux")]
 mod arch {
+    use indicatif::{ProgressBar, ProgressStyle};
+    use scopeguard;
+    use std::time::Duration;
+
     use super::*;
 
     pub const SPAWN_ERROR: &str = "could not spawn perf";
@@ -116,6 +120,20 @@ mod arch {
             command.arg(perf_output);
         }
 
+        // perf script can take a long time to run. Notify the user that it is running
+        // by using a spinner. Ensure that the spinner gets cleaned up regardless of how
+        // this function exits by using a scopeguard.
+        let spinner = ProgressBar::new_spinner().with_prefix("Running perf script");
+        spinner.set_style(
+            ProgressStyle::with_template("{prefix} [{elapsed}]: {spinner:.green}")
+                .unwrap()
+                .tick_strings(&[".", "..", "...", " ..", "  .", "", "✓"]),
+        );
+        spinner.enable_steady_tick(Duration::from_millis(500));
+        let _guard = scopeguard::guard(spinner, |spinner| {
+            spinner.finish();
+        });
+
         let output = command.output().context("unable to call perf script")?;
         if !output.status.success() {
             anyhow::bail!(format!(