Ensure onStdinClose only completes for non-tty streams

CHANGELOG.md

@@ -1,5 +1,11 @@
 ## 1.50.1
 
+### Command Line Interface
+
+* Fix a bug where moving the `--watch` command to the background would
+  unexpectedly cause the command to stop running unless the standard input
+  stream was a TTY.
+
 ### Embedded Sass
 
 * The JS embedded host and the embedded compiler will now properly avoid

lib/src/io/interface.dart

@@ -95,10 +95,12 @@ String? getEnvironmentVariable(String name) => throw '';
 int get exitCode => throw '';
 set exitCode(int value) => throw '';
 
-/// If stdin is a TTY, returns a [CancelableOperation] that completes once it
-/// closes.
+/// Returns a [CancelableOperation] that completes when stdin closes.
 ///
-/// Otherwise, returns a [CancelableOperation] that never completes.
+/// Note that if stdin is a TTY, the operation never completes. This is to
+/// avoid interfering with background job systems where reading from stdin
+/// and then moving the process to the background would incorrectly cause
+/// the job to stop.
 ///
 /// As long as this is uncanceled, it will monopolize stdin so that nothing else
 /// can read from it.

lib/src/io/node.dart

@@ -218,7 +218,7 @@ set exitCode(int code) => process.exitCode = code;
 
 CancelableOperation<void> onStdinClose() {
   var completer = CancelableCompleter<void>();
-  if (isStdinTTY == true) {
+  if (isStdinTTY != true) {
     process.stdin.on('end', allowInterop(() => completer.complete()));
   }
   return completer.operation;

lib/src/io/vm.dart

@@ -91,8 +91,8 @@ DateTime modificationTime(String path) {
 String? getEnvironmentVariable(String name) => io.Platform.environment[name];
 
 CancelableOperation<void> onStdinClose() => io.stdin.hasTerminal
-    ? CancelableOperation.fromSubscription(io.stdin.listen(null))
-    : CancelableCompleter<void>().operation;
+    ? CancelableCompleter<void>().operation
+    : CancelableOperation.fromSubscription(io.stdin.listen(null));
 
 Future<Stream<WatchEvent>> watchDir(String path, {bool poll = false}) async {
   var watcher = poll ? PollingDirectoryWatcher(path) : DirectoryWatcher(path);