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

@@ -23,6 +23,7 @@ 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"
 shlex = "1.1.0"

src/lib.rs

@@ -34,6 +34,9 @@ pub enum Workload {
 
 #[cfg(target_os = "linux")]
 mod arch {
+    use indicatif::{ProgressBar, ProgressStyle};
+    use std::time::Duration;
+
     use super::*;
 
     pub const SPAWN_ERROR: &str = "could not spawn perf";
@@ -116,7 +119,18 @@ mod arch {
             command.arg(perf_output);
         }
 
-        let output = command.output().context("unable to call perf script")?;
+        // perf script can take a long time to run. Notify the user that it is running
+        // by using a spinner. Note that if this function exits before calling
+        // spinner.finish(), then the spinner will be completely removed from the terminal.
+        let spinner = ProgressBar::new_spinner().with_prefix("Running perf script");
+        spinner.set_style(
+            ProgressStyle::with_template("{prefix} [{elapsed}]: {spinner:.green}").unwrap(),
+        );
+        spinner.enable_steady_tick(Duration::from_millis(500));
+
+        let result = command.output().context("unable to call perf script");
+        spinner.finish();
+        let output = result?;
         if !output.status.success() {
             anyhow::bail!(format!(
                 "unable to run 'perf script': ({}) {}",