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

@@ -1,3 +1,4 @@
+use indicatif::{ProgressBar, ProgressStyle};
 use std::{
     env,
     fs::File,
@@ -34,6 +35,8 @@ pub enum Workload {
 
 #[cfg(target_os = "linux")]
 mod arch {
+    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, so notify the user that it is running
+        // by using a spinner.
+        let spinner = ProgressBar::new_spinner().with_prefix("Running perf script");
+        spinner.set_style(ProgressStyle::with_template("{prefix}: {spinner} [{elapsed}]").unwrap());
+        spinner.enable_steady_tick(Duration::from_millis(80));
+
+        // Call perf script here, but if there is an error, do not exit the function until
+        // we have cleaned up the spinner. If there was no error running the command, process
+        // the status of the command and return its output.
+        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': ({}) {}",