[flutter_tools] exec rather than spawn subprocess from bin/internal/shared.sh (#99871)

bin/internal/shared.sh

@@ -222,10 +222,10 @@ function shared::execute() {
     flutter*)
       # FLUTTER_TOOL_ARGS aren't quoted below, because it is meant to be
       # considered as separate space-separated args.
-      "$DART" --disable-dart-dev --packages="$FLUTTER_TOOLS_DIR/.packages" $FLUTTER_TOOL_ARGS "$SNAPSHOT_PATH" "$@"
+      exec "$DART" --disable-dart-dev --packages="$FLUTTER_TOOLS_DIR/.packages" $FLUTTER_TOOL_ARGS "$SNAPSHOT_PATH" "$@"
       ;;
     dart*)
-      "$DART" "$@"
+      exec "$DART" "$@"
       ;;
     *)
       >&2 echo "Error! Executable name $BIN_NAME not recognized!"

packages/flutter_tools/test/integration.shard/bash_entrypoint_test.dart

@@ -0,0 +1,71 @@
+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:async';
+import 'dart:convert';
+
+import 'package:file/file.dart';
+import 'package:flutter_tools/src/base/io.dart';
+
+import '../src/common.dart';
+import 'test_utils.dart';
+
+final String flutterRootPath = getFlutterRoot();
+final Directory flutterRoot = fileSystem.directory(flutterRootPath);
+
+Future<void> main() async {
+  test('verify terminating flutter/bin/dart terminates the underlying dart process', () async {
+    final Completer<void> childReadyCompleter = Completer<void>();
+    String stdout = '';
+    final Process process = await processManager.start(
+        <String>[
+          dartBash.path,
+          listenForSigtermScript.path,
+        ],
+    );
+    final Future<Object?> stdoutFuture = process.stdout
+        .transform<String>(utf8.decoder)
+        .forEach((String str) {
+          stdout += str;
+          if (stdout.contains('Ready to receive signals') && !childReadyCompleter.isCompleted) {
+            childReadyCompleter.complete();
+          }
+        });
+    // Ensure that the child app has registered its signal handler
+    await childReadyCompleter.future;
+    final bool killSuccess = process.kill();
+    expect(killSuccess, true);
+    // Wait for stdout to complete
+    await stdoutFuture;
+    // Ensure child exited successfully
+    expect(
+        await process.exitCode,
+        0,
+        reason: 'child process exited with code ${await process.exitCode}, and '
+        'stdout:\n$stdout',
+    );
+    expect(stdout, contains('Successfully received SIGTERM!'));
+  },
+  skip: platform.isWindows); // [intended] Windows does not use the bash entrypoint
+}
+
+// A test Dart app that will run until it receives SIGTERM
+File get listenForSigtermScript {
+  return flutterRoot
+      .childDirectory('packages')
+      .childDirectory('flutter_tools')
+      .childDirectory('test')
+      .childDirectory('integration.shard')
+      .childDirectory('test_data')
+      .childFile('listen_for_sigterm.dart')
+      .absolute;
+}
+
+// The executable bash entrypoint for the Dart binary.
+File get dartBash {
+  return flutterRoot
+      .childDirectory('bin')
+      .childFile('dart')
+      .absolute;
+}

packages/flutter_tools/test/integration.shard/test_data/listen_for_sigterm.dart

@@ -0,0 +1,25 @@
+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:async';
+import 'package:flutter_tools/src/base/io.dart';
+
+// This application will log to STDOUT and exit with 0 when it receives the
+// SIGTERM signal.
+Future<void> main() async {
+  final Stdout stdout = Stdio().stdout;
+  final Stream<ProcessSignal> interruptStream = ProcessSignal.sigterm.watch();
+  interruptStream.listen((_) {
+    // The test should assert that this was logged
+    stdout.writeln('Successfully received SIGTERM!');
+    exit(0);
+  });
+  // The test should wait for this message before sending SIGTERM, or else the
+  // listener may not have been registered.
+  stdout.writeln('Ready to receive signals');
+
+  await Future<void>.delayed(const Duration(seconds: 10));
+  stdout.writeln('Did not receive SIGTERM!');
+  exit(1);
+}