[et] Adds a .bat entrypoint for Windows (#50784) For https://github.com/flutter/flutter/issues/132807

diff --git a/bin/et.bat b/bin/et.bat
new file mode 100644
index 0000000..b1236e2
--- /dev/null
+++ b/bin/et.bat

@@ -0,0 +1,40 @@
+@ECHO off

+REM Copyright 2013 The Flutter Authors. All rights reserved.

+REM Use of this source code is governed by a BSD-style license that can be

+REM found in the LICENSE file.

+

+REM ---------------------------------- NOTE ----------------------------------

+REM

+REM Please keep the logic in this file consistent with the logic in the

+REM `et` script in the same directory to ensure that it continues to

+REM work across all platforms!

+REM

+REM --------------------------------------------------------------------------

+

+SETLOCAL ENABLEDELAYEDEXPANSION

+

+FOR %%i IN ("%~dp0..\..") DO SET SRC_DIR=%%~fi

+

+REM Test if Git is available on the Host

+where /q git || ECHO Error: Unable to find git in your PATH. && EXIT /B 1

+

+SET repo_dir=%SRC_DIR%\flutter

+SET engine_tool_dir=%repo_dir%\tools\engine_tool

+

+REM Determine which platform we are on and use the right prebuilt Dart SDK

+IF "%PROCESSOR_ARCHITECTURE%"=="AMD64" (

+    SET dart_sdk_path=%SRC_DIR%\flutter\prebuilts\windows-x64\dart-sdk

+) ELSE IF "%PROCESSOR_ARCHITECTURE%"=="ARM64" (

+    SET dart_sdk_path=%SRC_DIR%\flutter\prebuilts\windows-arm64\dart-sdk

+) ELSE (

+    ECHO "Windows x86 (32-bit) is not supported" && EXIT /B 1

+)

+

+SET dart=%dart_sdk_path%\bin\dart.exe

+

+cd "%engine_tool_dir%"

+

+REM Do not use the CALL command in the next line to execute Dart. CALL causes

+REM Windows to re-read the line from disk after the CALL command has finished

+REM regardless of the ampersand chain.

+"%dart%" --disable-dart-dev bin\et.dart %* & exit /B !ERRORLEVEL!


diff --git a/tools/engine_tool/README.md b/tools/engine_tool/README.md
index 496824a..2a36eb9 100644
--- a/tools/engine_tool/README.md
+++ b/tools/engine_tool/README.md

@@ -23,7 +23,6 @@
 GitHub issue [here](https://github.com/flutter/flutter/issues/132807). Some
 desirable new features would do the following:
 
-* Support Windows hosts.
 * Add a `doctor` command.
 * Update the engine checkout so that engine developers no longer have to remeber
 to run `gclient sync -D`.

diff --git a/tools/engine_tool/lib/src/commands/command_runner.dart b/tools/engine_tool/lib/src/commands/command_runner.dart
index 360e649..48e306d 100644
--- a/tools/engine_tool/lib/src/commands/command_runner.dart
+++ b/tools/engine_tool/lib/src/commands/command_runner.dart

@@ -41,7 +41,7 @@
   @override
   Future<int> run(Iterable<String> args) async {
     try{
-      return await runCommand(parse(args)) ?? 1;
+      return await runCommand(parse(args)) ?? 0;
     } on FormatException catch (e) {
       environment.logger.error(e);
       return 1;

diff --git a/tools/engine_tool/test/entry_point_test.dart b/tools/engine_tool/test/entry_point_test.dart
new file mode 100644
index 0000000..052b361
--- /dev/null
+++ b/tools/engine_tool/test/entry_point_test.dart

@@ -0,0 +1,40 @@
+// Copyright 2013 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:io' as io;
+
+import 'package:engine_repo_tools/engine_repo_tools.dart';
+import 'package:litetest/litetest.dart';
+import 'package:path/path.dart' as path;
+import 'package:platform/platform.dart';
+import 'package:process_runner/process_runner.dart';
+
+void main() {
+  final Engine engine;
+  try {
+    engine = Engine.findWithin();
+  } catch (e) {
+    io.stderr.writeln(e);
+    io.exitCode = 1;
+    return;
+  }
+
+  test('The entry points under bin/ work', () async {
+    const Platform platform = LocalPlatform();
+    final ProcessRunner runner = ProcessRunner();
+    final String exe = platform.isWindows ? '.bat' : '';
+    final String entrypointPath = path.join(
+      engine.flutterDir.path, 'bin', 'et$exe',
+    );
+    final ProcessRunnerResult processResult = await runner.runProcess(
+      <String>[entrypointPath, 'help'],
+      failOk: true,
+    );
+    if (processResult.exitCode != 0) {
+      io.stdout.writeln(processResult.stdout);
+      io.stderr.writeln(processResult.stderr);
+    }
+    expect(processResult.exitCode, equals(0));
+  });
+}