feat(unstable): deno run --watch

cli/file_watcher.rs

@@ -0,0 +1,89 @@
+use crate::colors;
+use deno_core::ErrBox;
+use futures::stream::StreamExt;
+use futures::Future;
+use notify::event::Event as NotifyEvent;
+use notify::event::EventKind;
+use notify::Error as NotifyError;
+use notify::RecommendedWatcher;
+use notify::RecursiveMode;
+use notify::Watcher;
+use std::path::PathBuf;
+use std::pin::Pin;
+use tokio::select;
+use tokio::sync::mpsc;
+
+// TODO(bartlomieju): rename
+type WatchFuture =
+  Pin<Box<dyn Future<Output = std::result::Result<(), deno_core::ErrBox>>>>;
+
+async fn error_handler(watch_future: WatchFuture) {
+  let result = watch_future.await;
+  if let Err(err) = result {
+    let msg = format!("{}: {}", colors::red_bold("error"), err.to_string(),);
+    eprintln!("{}", msg);
+  }
+}
+
+pub async fn watch_func<F>(
+  watch_paths: &[PathBuf],
+  closure: F,
+) -> Result<(), ErrBox>
+where
+  F: Fn() -> WatchFuture,
+{
+  loop {
+    let func = error_handler(closure());
+    let mut is_file_changed = false;
+    select! {
+      _ = file_watcher(watch_paths) => {
+          is_file_changed = true;
+          info!(
+            "{} File change detected! Restarting!",
+            colors::intense_blue("Watcher")
+          );
+        },
+      _ = func => { },
+    };
+    if !is_file_changed {
+      info!(
+        "{} Process terminated! Restarting on file change...",
+        colors::intense_blue("Watcher")
+      );
+      file_watcher(watch_paths).await?;
+      info!(
+        "{} File change detected! Restarting!",
+        colors::intense_blue("Watcher")
+      );
+    }
+  }
+}
+
+pub async fn file_watcher(paths: &[PathBuf]) -> Result<(), deno_core::ErrBox> {
+  let (sender, mut receiver) = mpsc::channel::<Result<NotifyEvent, ErrBox>>(16);
+  let sender = std::sync::Mutex::new(sender);
+
+  let mut watcher: RecommendedWatcher =
+    Watcher::new_immediate(move |res: Result<NotifyEvent, NotifyError>| {
+      let res2 = res.map_err(ErrBox::from);
+      let mut sender = sender.lock().unwrap();
+      // Ignore result, if send failed it means that watcher was already closed,
+      // but not all messages have been flushed.
+      let _ = sender.try_send(res2);
+    })?;
+
+  for path in paths {
+    watcher.watch(path, RecursiveMode::NonRecursive)?;
+  }
+
+  while let Some(result) = receiver.next().await {
+    let event = result?;
+    match event.kind {
+      EventKind::Create(_) => break,
+      EventKind::Modify(_) => break,
+      EventKind::Remove(_) => break,
+      _ => continue,
+    }
+  }
+  Ok(())
+}

cli/flags.rs

@@ -123,6 +123,7 @@ pub struct Flags {
   pub unstable: bool,
   pub v8_flags: Option<Vec<String>>,
   pub version: bool,
+  pub watch: bool,
   pub write_allowlist: Vec<PathBuf>,
 }
 
@@ -562,6 +563,7 @@ fn run_parse(flags: &mut Flags, matches: &clap::ArgMatches) {
     flags.argv.push(v);
   }
 
+  flags.watch = matches.is_present("watch");
   flags.subcommand = DenoSubcommand::Run { script };
 }
 
@@ -1157,6 +1159,7 @@ fn run_test_args<'a, 'b>(app: App<'a, 'b>) -> App<'a, 'b> {
 
 fn run_subcommand<'a, 'b>() -> App<'a, 'b> {
   run_test_args(SubCommand::with_name("run"))
+    .arg(watch_arg())
     .setting(AppSettings::TrailingVarArg)
     .arg(script_arg())
     .about("Run a program given a filename or url to the module. Use '-' as a filename to read from stdin.")
@@ -1409,6 +1412,16 @@ fn v8_flags_arg_parse(flags: &mut Flags, matches: &ArgMatches) {
   }
 }
 
+fn watch_arg<'a, 'b>() -> Arg<'a, 'b> {
+  Arg::with_name("watch")
+    .long("watch")
+    .help("Watch for file changes and restart process automatically")
+    .long_help(
+      "Watch for file changes and restart process automatically.
+Only local files from entry point module graph are watched.",
+    )
+}
+
 fn no_check_arg<'a, 'b>() -> Arg<'a, 'b> {
   Arg::with_name("no-check")
     .long("no-check")
@@ -1560,6 +1573,22 @@ mod tests {
     );
   }
 
+  #[test]
+  fn run_watch() {
+    let r = flags_from_vec_safe(svec!["deno", "run", "--watch", "script.ts"]);
+    let flags = r.unwrap();
+    assert_eq!(
+      flags,
+      Flags {
+        subcommand: DenoSubcommand::Run {
+          script: "script.ts".to_string(),
+        },
+        watch: true,
+        ..Flags::default()
+      }
+    );
+  }
+
   #[test]
   fn run_reload_allow_write() {
     let r = flags_from_vec_safe(svec![

cli/main.rs

@@ -30,6 +30,7 @@ mod diff;
 mod disk_cache;
 pub mod errors;
 mod file_fetcher;
+mod file_watcher;
 pub mod flags;
 mod flags_allow_net;
 mod fmt;
@@ -229,6 +230,8 @@ async fn cache_command(flags: Flags, files: Vec<String>) -> Result<(), ErrBox> {
 
   for file in files {
     let specifier = ModuleSpecifier::resolve_url_or_path(&file)?;
+    // TODO(bartlomieju): don't use `preload_module` in favor of calling "GlobalState::prepare_module_load()"
+    // explicitly? Seems wasteful to create multiple worker just to run TS compiler
     worker.preload_module(&specifier).await.map(|_| ())?;
   }
 
@@ -436,33 +439,29 @@ async fn run_repl(flags: Flags) -> Result<(), ErrBox> {
   }
 }
 
-async fn run_command(flags: Flags, script: String) -> Result<(), ErrBox> {
+async fn run_from_stdin(flags: Flags) -> Result<(), ErrBox> {
   let global_state = GlobalState::new(flags.clone())?;
-  let main_module = if script != "-" {
-    ModuleSpecifier::resolve_url_or_path(&script).unwrap()
-  } else {
-    ModuleSpecifier::resolve_url_or_path("./__$deno$stdin.ts").unwrap()
-  };
+  let main_module =
+    ModuleSpecifier::resolve_url_or_path("./__$deno$stdin.ts").unwrap();
   let mut worker =
     MainWorker::create(&global_state.clone(), main_module.clone())?;
-  if script == "-" {
-    let mut source = Vec::new();
-    std::io::stdin().read_to_end(&mut source)?;
-    let main_module_url = main_module.as_url().to_owned();
-    // Create a dummy source file.
-    let source_file = SourceFile {
-      filename: main_module_url.to_file_path().unwrap(),
-      url: main_module_url,
-      types_header: None,
-      media_type: MediaType::TypeScript,
-      source_code: source.into(),
-    };
-    // Save our fake file into file fetcher cache
-    // to allow module access by TS compiler
-    global_state
-      .file_fetcher
-      .save_source_file_in_cache(&main_module, source_file);
+
+  let mut source = Vec::new();
+  std::io::stdin().read_to_end(&mut source)?;
+  let main_module_url = main_module.as_url().to_owned();
+  // Create a dummy source file.
+  let source_file = SourceFile {
+    filename: main_module_url.to_file_path().unwrap(),
+    url: main_module_url,
+    types_header: None,
+    media_type: MediaType::TypeScript,
+    source_code: source.into(),
   };
+  // Save our fake file into file fetcher cache
+  // to allow module access by TS compiler
+  global_state
+    .file_fetcher
+    .save_source_file_in_cache(&main_module, source_file);
 
   debug!("main_module {}", main_module);
   worker.execute_module(&main_module).await?;
@@ -472,6 +471,69 @@ async fn run_command(flags: Flags, script: String) -> Result<(), ErrBox> {
   Ok(())
 }
 
+async fn run_with_watch(flags: Flags, script: String) -> Result<(), ErrBox> {
+  let main_module = ModuleSpecifier::resolve_url_or_path(&script)?;
+  let global_state = GlobalState::new(flags.clone())?;
+
+  let mut module_graph_loader = module_graph::ModuleGraphLoader::new(
+    global_state.file_fetcher.clone(),
+    global_state.maybe_import_map.clone(),
+    Permissions::allow_all(),
+    false,
+    false,
+  );
+  module_graph_loader.add_to_graph(&main_module, None).await?;
+  let module_graph = module_graph_loader.get_graph();
+
+  // Find all local files in graph
+  let paths_to_watch: Vec<PathBuf> = module_graph
+    .values()
+    .map(|f| Url::parse(&f.url).unwrap())
+    .filter(|url| url.scheme() == "file")
+    .map(|url| url.to_file_path().unwrap())
+    .collect();
+
+  // FIXME(bartlomieju): new file watcher is created on after each restart
+  file_watcher::watch_func(&paths_to_watch, move || {
+    // FIXME(bartlomieju): GlobalState must be created on each restart - otherwise file fetcher
+    // will use cached source files
+    let gs = GlobalState::new(flags.clone()).unwrap();
+    let main_module = main_module.clone();
+    async move {
+      let mut worker = MainWorker::create(&gs, main_module.clone())?;
+      debug!("main_module {}", main_module);
+      worker.execute_module(&main_module).await?;
+      worker.execute("window.dispatchEvent(new Event('load'))")?;
+      (&mut *worker).await?;
+      worker.execute("window.dispatchEvent(new Event('unload'))")?;
+      Ok(())
+    }
+    .boxed_local()
+  })
+  .await
+}
+
+async fn run_command(flags: Flags, script: String) -> Result<(), ErrBox> {
+  // Read script content from stdin
+  if script == "-" {
+    return run_from_stdin(flags).await;
+  }
+
+  if flags.watch {
+    return run_with_watch(flags, script).await;
+  }
+
+  let main_module = ModuleSpecifier::resolve_url_or_path(&script)?;
+  let global_state = GlobalState::new(flags.clone())?;
+  let mut worker = MainWorker::create(&global_state, main_module.clone())?;
+  debug!("main_module {}", main_module);
+  worker.execute_module(&main_module).await?;
+  worker.execute("window.dispatchEvent(new Event('load'))")?;
+  (&mut *worker).await?;
+  worker.execute("window.dispatchEvent(new Event('unload'))")?;
+  Ok(())
+}
+
 async fn test_command(
   flags: Flags,
   include: Option<Vec<String>>,

cli/tests/integration_tests.rs

@@ -981,6 +981,41 @@ fn info_with_compiled_source() {
   assert_eq!(output.stderr, b"");
 }
 
+#[test]
+fn run_watch() {
+  let t = TempDir::new().expect("tempdir fail");
+  let file_to_watch = t.path().join("file_to_watch.js");
+  std::fs::write(&file_to_watch, "console.log('Hello world');")
+    .expect("error writing file");
+
+  let mut child = util::deno_cmd()
+    .current_dir(util::root_path())
+    .arg("run")
+    .arg("--watch")
+    .arg(&file_to_watch)
+    .stdout(std::process::Stdio::piped())
+    .spawn()
+    .expect("failed to spawn script");
+
+  let stdout = child.stdout.as_mut().unwrap();
+  let mut stdout_lines =
+    std::io::BufReader::new(stdout).lines().map(|r| r.unwrap());
+
+  assert!(stdout_lines.next().unwrap().contains("Hello world"));
+  assert!(stdout_lines.next().unwrap().contains("Process terminated"));
+
+  // Change content of the file
+  std::fs::write(&file_to_watch, "console.log('Hello world2');")
+    .expect("error writing file");
+
+  assert!(stdout_lines.next().unwrap().contains("Restarting"));
+  assert!(stdout_lines.next().unwrap().contains("Hello world2"));
+  assert!(stdout_lines.next().unwrap().contains("Process terminated"));
+
+  child.kill().unwrap();
+  drop(t);
+}
+
 #[test]
 fn repl_test_console_log() {
   let (out, err) = util::run_and_collect_output(