Teach flutter msbuild for Windows (#32335)

Eliminates the need for a build.bat in the Windows build workflow, adding
preliminary support for building using msbuild. The handling of
vcvars64.bat may be refined in the future, but this serves as a starting point.

packages/flutter_tools/lib/src/project.dart

@@ -592,13 +592,19 @@ class WindowsProject {
 
   final FlutterProject project;
 
-  bool existsSync() => project.directory.childDirectory('windows').existsSync();
+  bool existsSync() => _editableDirectory.existsSync();
 
-  // Note: The build script file exists as a temporary shim.
-  File get buildScript => project.directory.childDirectory('windows').childFile('build.bat');
+  Directory get _editableDirectory => project.directory.childDirectory('windows');
+
+  /// Contains definitions for FLUTTER_ROOT, LOCAL_ENGINE, and more flags for
+  /// the build.
+  File get generatedPropertySheetFile => _editableDirectory.childDirectory('flutter').childFile('Generated.props');
+
+  // The MSBuild project file.
+  File get vcprojFile => _editableDirectory.childFile('Runner.vcxproj');
 
   // Note: The name script file exists as a temporary shim.
-  File get nameScript => project.directory.childDirectory('windows').childFile('name_output.bat');
+  File get nameScript => _editableDirectory.childFile('name_output.bat');
 }
 
 /// The Linux sub project.

packages/flutter_tools/lib/src/windows/build_windows.dart

@@ -11,14 +11,26 @@ import '../cache.dart';
 import '../convert.dart';
 import '../globals.dart';
 import '../project.dart';
+import 'msbuild_utils.dart';
 
-/// Builds the Windows project through the project bat script.
+/// Builds the Windows project using msbuild.
 Future<void> buildWindows(WindowsProject windowsProject, BuildInfo buildInfo) async {
+  final Map<String, String> environment = <String, String>{
+    'FLUTTER_ROOT': Cache.flutterRoot,
+    'EXTRA_BUNDLE_FLAGS': buildInfo?.trackWidgetCreation == true ? '--track-widget-creation' : '',
+  };
+  writePropertySheet(windowsProject.generatedPropertySheetFile, environment);
+
+  final String vcvarsScript = await findVcvars();
+  if (vcvarsScript == null) {
+    throwToolExit('Unable to build: could not find vcvars64.bat');
+  }
+
+  final String configuration = buildInfo.isDebug ? 'Debug' : 'Release';
   final Process process = await processManager.start(<String>[
-    windowsProject.buildScript.path,
-    Cache.flutterRoot,
-    buildInfo.isDebug ? 'debug' : 'release',
-    buildInfo?.trackWidgetCreation == true ? 'track-widget-creation' : 'no-track-widget-creation',
+    vcvarsScript, '&&', 'msbuild',
+    windowsProject.vcprojFile.path,
+    '/p:Configuration=$configuration',
   ], runInShell: true);
   final Status status = logger.startProgress(
     'Building Windows application...',

packages/flutter_tools/lib/src/windows/msbuild_utils.dart

+// Copyright 2019 The Chromium 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 'package:xml/xml.dart' as xml;
+
+import '../base/file_system.dart';
+import '../base/io.dart';
+import '../base/platform.dart';
+import '../base/process_manager.dart';
+
+/// The supported versions of Visual Studio.
+const List<String> _visualStudioVersions = <String>['2017', '2019'];
+
+/// The supported flavors of Visual Studio.
+const List<String> _visualStudioFlavors = <String>[
+  'Community',
+  'Professional',
+  'Enterprise',
+  'Preview'
+];
+
+/// Returns the path to an installed vcvars64.bat script if found, or null.
+Future<String> findVcvars() async {
+  final String programDir = platform.environment['PROGRAMFILES(X86)'];
+  final String pathPrefix = fs.path.join(programDir, 'Microsoft Visual Studio');
+  const String vcvarsScriptName = 'vcvars64.bat';
+  final String pathSuffix =
+      fs.path.join('VC', 'Auxiliary', 'Build', vcvarsScriptName);
+  for (final String version in _visualStudioVersions) {
+    for (final String flavor in _visualStudioFlavors) {
+      final String testPath =
+          fs.path.join(pathPrefix, version, flavor, pathSuffix);
+      if (fs.file(testPath).existsSync()) {
+        return testPath;
+      }
+    }
+  }
+
+  // If it can't be found manually, check the path.
+  final ProcessResult whereResult = await processManager.run(<String>[
+    'where.exe',
+    vcvarsScriptName,
+  ]);
+  if (whereResult.exitCode == 0) {
+    return whereResult.stdout.trim();
+  }
+
+  return null;
+}
+
+/// Writes a property sheet (.props) file to expose all of the key/value
+/// pairs in [variables] as enivornment variables.
+void writePropertySheet(File propertySheetFile, Map<String, String> variables) {
+  final xml.XmlBuilder builder = xml.XmlBuilder();
+  builder.processing('xml', 'version="1.0" encoding="utf-8"');
+  builder.element('Project', nest: () {
+    builder.attribute('ToolsVersion', '4.0');
+    builder.attribute(
+        'xmlns', 'http://schemas.microsoft.com/developer/msbuild/2003');
+    builder.element('ImportGroup', nest: () {
+      builder.attribute('Label', 'PropertySheets');
+    });
+    _addUserMacros(builder, variables);
+    builder.element('PropertyGroup');
+    builder.element('ItemDefinitionGroup');
+    _addItemGroup(builder, variables);
+  });
+
+  propertySheetFile.createSync(recursive: true);
+  propertySheetFile.writeAsStringSync(
+      builder.build().toXmlString(pretty: true, indent: '  '));
+}
+
+/// Adds the UserMacros PropertyGroup that defines [variables] to [builder].
+void _addUserMacros(xml.XmlBuilder builder, Map<String, String> variables) {
+  builder.element('PropertyGroup', nest: () {
+    builder.attribute('Label', 'UserMacros');
+    for (final MapEntry<String, String> variable in variables.entries) {
+      builder.element(variable.key, nest: () {
+        builder.text(variable.value);
+      });
+    }
+  });
+}
+
+/// Adds the ItemGroup to expose the given [variables] as environment variables
+/// to [builder].
+void _addItemGroup(xml.XmlBuilder builder, Map<String, String> variables) {
+  builder.element('ItemGroup', nest: () {
+    for (final String name in variables.keys) {
+      builder.element('BuildMacro', nest: () {
+        builder.attribute('Include', name);
+        builder.element('Value', nest: () {
+          builder.text('\$($name)');
+        });
+        builder.element('EnvironmentVariable', nest: () {
+          builder.text('true');
+        });
+      });
+    }
+  });
+}

packages/flutter_tools/test/commands/build_windows_test.dart

@@ -11,6 +11,7 @@ import 'package:flutter_tools/src/cache.dart';
 import 'package:flutter_tools/src/commands/build.dart';
 import 'package:mockito/mockito.dart';
 import 'package:process/process.dart';
+import 'package:xml/xml.dart' as xml;
 
 import '../src/common.dart';
 import '../src/context.dart';
@@ -21,8 +22,12 @@ void main() {
   final MockProcessManager mockProcessManager = MockProcessManager();
   final MemoryFileSystem memoryFilesystem = MemoryFileSystem(style: FileSystemStyle.windows);
   final MockProcess mockProcess = MockProcess();
-  final MockPlatform windowsPlatform = MockPlatform();
+  final MockPlatform windowsPlatform = MockPlatform()
+      ..environment['PROGRAMFILES(X86)'] = r'C:\Program Files (x86)\';
   final MockPlatform notWindowsPlatform = MockPlatform();
+  const String projectPath = r'windows\Runner.vcxproj';
+  // A vcvars64.bat location that will be found by the lookup method.
+  const String vcvarsPath = r'C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build\vcvars64.bat';
 
   when(mockProcess.exitCode).thenAnswer((Invocation invocation) async {
     return 0;
@@ -36,9 +41,22 @@ void main() {
   when(windowsPlatform.isWindows).thenReturn(true);
   when(notWindowsPlatform.isWindows).thenReturn(false);
 
+  testUsingContext('Windows build fails when there is no vcvars64.bat', () async {
+    final BuildCommand command = BuildCommand();
+    applyMocksToCommand(command);
+    fs.file(projectPath).createSync(recursive: true);
+    expect(createTestCommandRunner(command).run(
+      const <String>['build', 'windows']
+    ), throwsA(isInstanceOf<ToolExit>()));
+  }, overrides: <Type, Generator>{
+    Platform: () => windowsPlatform,
+    FileSystem: () => memoryFilesystem,
+  });
+
   testUsingContext('Windows build fails when there is no windows project', () async {
     final BuildCommand command = BuildCommand();
     applyMocksToCommand(command);
+    fs.file(vcvarsPath).createSync(recursive: true);
     expect(createTestCommandRunner(command).run(
       const <String>['build', 'windows']
     ), throwsA(isInstanceOf<ToolExit>()));
@@ -50,7 +68,8 @@ void main() {
   testUsingContext('Windows build fails on non windows platform', () async {
     final BuildCommand command = BuildCommand();
     applyMocksToCommand(command);
-    fs.file(r'windows\build.bat').createSync(recursive: true);
+    fs.file(projectPath).createSync(recursive: true);
+    fs.file(vcvarsPath).createSync(recursive: true);
     fs.file('pubspec.yaml').createSync();
     fs.file('.packages').createSync();
 
@@ -62,17 +81,20 @@ void main() {
     FileSystem: () => memoryFilesystem,
   });
 
-  testUsingContext('Windows build invokes build script', () async {
+  testUsingContext('Windows build invokes msbuild and writes generated files', () async {
     final BuildCommand command = BuildCommand();
     applyMocksToCommand(command);
-    fs.file(r'windows\build.bat').createSync(recursive: true);
+    fs.file(projectPath).createSync(recursive: true);
+    fs.file(vcvarsPath).createSync(recursive: true);
     fs.file('pubspec.yaml').createSync();
     fs.file('.packages').createSync();
+
     when(mockProcessManager.start(<String>[
-      r'C:\windows\build.bat',
-      r'C:\',
-      'release',
-      'no-track-widget-creation',
+      vcvarsPath,
+      '&&',
+      'msbuild',
+      'C:\\$projectPath',
+      '/p:Configuration=Release',
     ], runInShell: true)).thenAnswer((Invocation invocation) async {
       return mockProcess;
     });
@@ -80,6 +102,14 @@ void main() {
     await createTestCommandRunner(command).run(
       const <String>['build', 'windows']
     );
+
+    // Spot-check important elemenst from the properties file.
+    final File propsFile = fs.file(r'C:\windows\flutter\Generated.props');
+    expect(propsFile.existsSync(), true);
+    final xml.XmlDocument props = xml.parse(propsFile.readAsStringSync());
+    expect(props.findAllElements('PropertyGroup').first.getAttribute('Label'), 'UserMacros');
+    expect(props.findAllElements('ItemGroup').length, 1);
+    expect(props.findAllElements('FLUTTER_ROOT').first.text, r'C:\');
   }, overrides: <Type, Generator>{
     FileSystem: () => memoryFilesystem,
     ProcessManager: () => mockProcessManager,