Close watcher by sending EOF

Author: nojaf

rewatch/src/watcher.rs

@@ -14,9 +14,11 @@ use futures_timer::Delay;
 use notify::event::ModifyKind;
 use notify::{Config, Error, Event, EventKind, RecommendedWatcher, RecursiveMode, Watcher};
 use std::collections::HashMap;
+use std::io::{IsTerminal, Read};
 use std::path::{Path, PathBuf};
 use std::sync::Arc;
 use std::sync::Mutex;
+use std::sync::atomic::{AtomicBool, Ordering};
 use std::time::{Duration, Instant, SystemTime};
 
 #[derive(Debug, Clone, PartialEq, Eq, Copy)]
@@ -208,6 +210,19 @@ async fn async_watch(
     })
     .expect("Error setting Ctrl-C handler");
 
+    // When stdin is a pipe (not a TTY), monitor it for EOF so that the
+    // parent process can signal a graceful shutdown by closing stdin.
+    let stdin_closed = Arc::new(AtomicBool::new(false));
+    let stdin_closed_clone = Arc::clone(&stdin_closed);
+    if !std::io::stdin().is_terminal() {
+        std::thread::spawn(move || {
+            let mut buf = [0u8; 1];
+            // This blocks until EOF (Ok(0)) or an error occurs.
+            let _ = std::io::stdin().read(&mut buf);
+            stdin_closed.store(true, Ordering::Relaxed);
+        });
+    }
+
     let mut initial_build = true;
 
     // Track file mtimes to deduplicate events.
@@ -217,7 +232,7 @@ async fn async_watch(
     let mut last_mtime: HashMap<PathBuf, SystemTime> = HashMap::new();
 
     loop {
-        if *ctrlc_pressed_clone.lock().unwrap() {
+        if *ctrlc_pressed_clone.lock().unwrap() || stdin_closed_clone.load(Ordering::Relaxed) {
             if show_progress {
                 println!("\nExiting...");
             }

tests/rewatch_tests/helpers/process.mjs

@@ -1,6 +1,4 @@
 import child_process from "node:child_process";
-import { unlink } from "node:fs/promises";
-import path from "node:path";
 import { bsc_exe, rescript_exe, runtimePath } from "./bins.mjs";
 
 /**
@@ -82,7 +80,7 @@ export function createRescriptCli(cwd, otelEndpoint) {
 
       const proc = child_process.spawn(rescript_exe, ["watch", ...args], {
         cwd,
-        stdio: ["ignore", "pipe", "pipe"],
+        stdio: ["pipe", "pipe", "pipe"],
         env,
         signal,
       });
@@ -118,21 +116,16 @@ export function createRescriptCli(cwd, otelEndpoint) {
       return {
         /**
          * Stop the watch process gracefully.
-         * Removes lib/rescript.lock to signal rewatch to exit, then polls
-         * for the process to exit. Falls back to AbortController if the
-         * process doesn't exit within the timeout.
+         * Closes stdin to signal EOF, which rewatch detects and exits.
+         * Falls back to AbortController if the process doesn't exit
+         * within the timeout.
          * @returns {Promise<void>}
          */
         async stop() {
           if (exited) return;
 
-          // Signal graceful shutdown by removing the lock file
-          const lockFile = path.join(cwd, "lib", "rescript.lock");
-          try {
-            await unlink(lockFile);
-          } catch {
-            // Lock file may not exist
-          }
+          // Signal graceful shutdown by closing stdin (EOF)
+          proc.stdin.end();
 
           // Poll for graceful exit
           const deadline = Date.now() + 5000;