[flutter_tools] add flutterRoot field to JSON machine output (#62053)

packages/flutter_tools/lib/src/runner/flutter_command_runner.dart

@@ -317,7 +317,11 @@ class FlutterCommandRunner extends CommandRunner<void> {
           globals.flutterVersion.fetchTagsAndUpdate();
           String status;
           if (machineFlag) {
-            status = const JsonEncoder.withIndent('  ').convert(globals.flutterVersion.toJson());
+            final Map<String, Object> jsonOut = globals.flutterVersion.toJson();
+            if (jsonOut != null) {
+              jsonOut['flutterRoot'] = Cache.flutterRoot;
+            }
+            status = const JsonEncoder.withIndent('  ').convert(jsonOut);
           } else {
             status = globals.flutterVersion.toString();
           }

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

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:convert';
+
 import 'package:flutter_tools/src/base/file_system.dart';
 import 'package:flutter_tools/src/base/io.dart';
 import 'package:flutter_tools/src/features.dart';
@@ -128,4 +130,21 @@ void main() {
     // Only printed by verbose tool.
     expect(result.stdout, isNot(contains('exiting with code 0')));
   });
+
+  test('flutter --version --machine outputs JSON with flutterRoot', () async {
+    final String flutterBin = globals.fs.path.join(getFlutterRoot(), 'bin', 'flutter');
+    final ProcessResult result = await const LocalProcessManager().run(<String>[
+      flutterBin,
+      '--version',
+      '--machine',
+    ]);
+
+    final Map<String, Object> versionInfo = json.decode(result.stdout
+      .toString()
+      .replaceAll('Building flutter tool...', '')
+      .replaceAll('Waiting for another flutter command to release the startup lock...', '')
+      .trim()) as Map<String, Object>;
+
+    expect(versionInfo, containsPair('flutterRoot', isNotNull));
+  });
 }