fix: drain stdout pipe to prevent project listing deadlock (#106)

The list_gcloud_projects() function piped stdout from `gcloud projects
list` but only read it after the child process exited. When a user has
enough GCP projects that the output exceeds the OS pipe buffer (~64KB),
gcloud blocks on write, the parent blocks waiting for exit, and neither
side makes progress — hitting the 10s timeout.

Spawn a thread to drain stdout concurrently so the pipe buffer never
fills up while the main thread polls for process completion.

Fixes googleworkspace/cli#96

.changeset/fix-project-listing-deadlock.md

@@ -0,0 +1,11 @@
+---
+"@googleworkspace/cli": patch
+---
+
+fix: drain stdout pipe to prevent project listing timeout during auth setup
+
+Fixed `gws auth setup` timing out at step 3 (GCP project selection) for users
+with many projects. The `gcloud projects list` stdout pipe was only read after
+the child process exited, causing a deadlock when output exceeded the OS pipe
+buffer (~64 KB). Stdout is now drained in a background thread to prevent the
+pipe from filling up.

src/setup.rs

@@ -545,6 +545,16 @@ fn list_gcloud_projects() -> (Vec<(String, String)>, Option<String>) {
         Err(e) => return (Vec::new(), Some(format!("Failed to run gcloud: {e}"))),
     };
 
+    // Drain stdout in a background thread to prevent pipe buffer deadlock.
+    // Without this, gcloud blocks once the OS pipe buffer (~64 KB) fills up,
+    // and the parent blocks waiting for gcloud to exit — a classic deadlock.
+    let stdout = child.stdout.take().expect("stdout was piped");
+    let reader_handle = std::thread::spawn(move || {
+        let mut buf = String::new();
+        std::io::Read::read_to_string(&mut { stdout }, &mut buf).ok();
+        buf
+    });
+
     // Wait with timeout
     let timeout = std::time::Duration::from_secs(10);
     let start = std::time::Instant::now();
@@ -552,15 +562,7 @@ fn list_gcloud_projects() -> (Vec<(String, String)>, Option<String>) {
         match child.try_wait() {
             Ok(Some(status)) => {
                 if status.success() {
-                    let stdout = child
-                        .stdout
-                        .take()
-                        .map(|mut s| {
-                            let mut buf = String::new();
-                            std::io::Read::read_to_string(&mut s, &mut buf).ok();
-                            buf
-                        })
-                        .unwrap_or_default();
+                    let stdout = reader_handle.join().unwrap_or_default();
                     let projects = stdout
                         .lines()
                         .filter_map(|line| {