Add --version-json to flutter CLI (#10538)

closes https://github.com/flutter/flutter/issues/10534

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

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 import 'dart:async';
+import 'dart:convert';
 
 import 'package:args/args.dart';
 import 'package:args/command_runner.dart';
@@ -59,6 +60,9 @@ class FlutterCommandRunner extends CommandRunner<Null> {
     argParser.addFlag('version',
         negatable: false,
         help: 'Reports the version of this tool.');
+    argParser.addFlag('json',
+        negatable: false,
+        hide: true);
     argParser.addFlag('color',
         negatable: true,
         hide: !verboseHelp,
@@ -255,10 +259,21 @@ class FlutterCommandRunner extends CommandRunner<Null> {
 
     if (globalResults['version']) {
       flutterUsage.sendCommand('version');
-      printStatus(FlutterVersion.instance.toString());
+      String status;
+      if (globalResults['json']) {
+        status = const JsonEncoder.withIndent('  ').convert(FlutterVersion.instance.toJson());
+      } else {
+        status = FlutterVersion.instance.toString();
+      }
+      printStatus(status);
       return;
     }
 
+    if (globalResults['json']) {
+      printError('The --json flag is only valid with the --version flag.');
+      throw new ProcessExit(2);
+    }
+
     await super.runCommand(globalResults);
   }
 

packages/flutter_tools/lib/src/version.dart

@@ -82,6 +82,15 @@ class FlutterVersion {
     return '$flutterText\n$frameworkText\n$engineText\n$toolsText';
   }
 
+  Map<String, Object> toJson() => <String, Object>{
+        'channel': channel,
+        'repositoryUrl': repositoryUrl ?? 'unknown source',
+        'frameworkRevision': frameworkRevision,
+        'frameworkCommitDate': frameworkCommitDate,
+        'engineRevision': engineRevision,
+        'dartSdkVersion': dartSdkVersion,
+      };
+
   /// A date String describing the last framework commit.
   String get frameworkCommitDate => _latestGitCommitDate();