feat(rustup-init): (wip) use process().stderr() as a tracing output

Author: rami3l

src/bin/rustup-init.rs

@@ -27,7 +27,9 @@ use rustup::cli::rustup_mode;
 #[cfg(windows)]
 use rustup::cli::self_update;
 use rustup::cli::setup_mode;
-use rustup::currentprocess::{process, varsource::VarSource, with_runtime, OSProcess};
+use rustup::currentprocess::{
+    filesource::StderrSource, process, varsource::VarSource, with_runtime, OSProcess,
+};
 use rustup::env_var::RUST_RECURSION_COUNT_MAX;
 use rustup::is_proxyable_tools;
 use rustup::utils::utils::{self, ExitCode};
@@ -68,7 +70,9 @@ async fn maybe_trace_rustup() -> Result<utils::ExitCode> {
             trace::{self, Sampler},
             Resource,
         };
-        use tracing_subscriber::{layer::SubscriberExt, EnvFilter, Registry};
+        use tracing_subscriber::{fmt, layer::SubscriberExt, EnvFilter, Registry};
+
+        let curr_process = process();
 
         global::set_text_map_propagator(TraceContextPropagator::new());
         let tracer = opentelemetry_otlp::new_pipeline()
@@ -86,7 +90,14 @@ async fn maybe_trace_rustup() -> Result<utils::ExitCode> {
             .install_batch(opentelemetry_sdk::runtime::Tokio)?;
         let env_filter = EnvFilter::try_from_default_env().unwrap_or(EnvFilter::new("INFO"));
         let telemetry = tracing_opentelemetry::layer().with_tracer(tracer);
-        let subscriber = Registry::default().with(env_filter).with(telemetry);
+        let subscriber = Registry::default()
+            .with(
+                fmt::layer()
+                    .with_ansi(curr_process.stderr().is_a_tty())
+                    .with_writer(move || curr_process.stderr()),
+            )
+            .with(env_filter)
+            .with(telemetry);
         tracing::subscriber::set_global_default(subscriber)?;
         let result = run_rustup().await;
         // We're tracing, so block until all spans are exported.