Fix analysis throwing string (#91435)

packages/flutter_tools/lib/src/commands/analyze_once.dart

@@ -125,7 +125,12 @@ class AnalyzeOnce extends AnalyzeBase {
       // Completing the future in the callback can't fail.
       unawaited(server.onExit.then<void>((int exitCode) {
         if (!analysisCompleter.isCompleted) {
-          analysisCompleter.completeError('analysis server exited: $exitCode');
+          analysisCompleter.completeError(
+            // Include the last 20 lines of server output in exception message
+            Exception(
+              'analysis server exited with code $exitCode and output:\n${server.getLogs(20)}',
+            ),
+          );
         }
       }));
 

packages/flutter_tools/lib/src/dart/analysis.dart

@@ -79,7 +79,7 @@ class AnalysisServer {
     final Stream<String> errorStream = _process!.stderr
         .transform<String>(utf8.decoder)
         .transform<String>(const LineSplitter());
-    errorStream.listen(_logger.printError);
+    errorStream.listen(_handleError);
 
     final Stream<String> inStream = _process!.stdout
         .transform<String>(utf8.decoder)
@@ -94,6 +94,28 @@ class AnalysisServer {
         <String, dynamic>{'included': directories, 'excluded': <String>[]});
   }
 
+  final List<String> _logs = <String>[];
+
+  /// Aggregated STDOUT and STDERR logs from the server.
+  ///
+  /// This can be surfaced to the user if the server crashes. If [tail] is null,
+  /// returns all logs, else only the last [tail] lines.
+  String getLogs([int? tail]) {
+    if (tail == null) {
+      return _logs.join('\n');
+    }
+    // Since List doesn't implement a .tail() method, we reverse it then use
+    // .take()
+    final Iterable<String> reversedLogs = _logs.reversed;
+    final List<String> firstTailLogs = reversedLogs.take(tail).toList();
+    return firstTailLogs.reversed.join('\n');
+  }
+
+  void _handleError(String message) {
+    _logs.add('[stderr] $message');
+    _logger.printError(message);
+  }
+
   bool get didServerErrorOccur => _didServerErrorOccur;
 
   Stream<bool> get onAnalyzing => _analyzingController.stream;
@@ -113,6 +135,7 @@ class AnalysisServer {
   }
 
   void _handleServerResponse(String line) {
+    _logs.add('[stdout] $line');
     _logger.printTrace('<== $line');
 
     final dynamic response = json.decode(line);

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

@@ -312,7 +312,6 @@ class FlutterCommandRunner extends CommandRunner<void> {
       return <String>[];
     }
 
-
     final List<String> projectPaths = globals.fs.directory(rootPath)
       .listSync(followLinks: false)
       .expand((FileSystemEntity entity) {

packages/flutter_tools/test/commands.shard/hermetic/analyze_test.dart

@@ -4,15 +4,25 @@
 
 // @dart = 2.8
 
+import 'package:args/command_runner.dart';
 import 'package:file/file.dart';
 import 'package:file/memory.dart';
+import 'package:flutter_tools/src/artifacts.dart';
+import 'package:flutter_tools/src/base/logger.dart';
+import 'package:flutter_tools/src/base/platform.dart';
+import 'package:flutter_tools/src/base/terminal.dart';
 import 'package:flutter_tools/src/cache.dart';
+import 'package:flutter_tools/src/commands/analyze.dart';
 import 'package:flutter_tools/src/commands/analyze_base.dart';
 import 'package:flutter_tools/src/dart/analysis.dart';
 
 import '../../src/common.dart';
+import '../../src/context.dart';
+import '../../src/fake_process_manager.dart';
+import '../../src/test_flutter_command_runner.dart';
 
 const String _kFlutterRoot = '/data/flutter';
+const int SIGABRT = -6;
 
 void main() {
   testWithoutContext('analyze generate correct errors message', () async {
@@ -35,6 +45,80 @@ void main() {
     );
   });
 
+  group('analyze command', () {
+    FileSystem fileSystem;
+    Platform platform;
+    BufferLogger logger;
+    FakeProcessManager processManager;
+    Terminal terminal;
+    AnalyzeCommand command;
+    CommandRunner<void> runner;
+
+    setUpAll(() {
+      Cache.disableLocking();
+    });
+
+    setUp(() {
+      fileSystem = MemoryFileSystem.test();
+      platform = FakePlatform();
+      logger = BufferLogger.test();
+      processManager = FakeProcessManager.empty();
+      terminal = Terminal.test();
+      command = AnalyzeCommand(
+        artifacts: Artifacts.test(),
+        fileSystem: fileSystem,
+        logger: logger,
+        platform: platform,
+        processManager: processManager,
+        terminal: terminal,
+      );
+      runner = createTestCommandRunner(command);
+
+      // Setup repo roots
+      const String homePath = '/home/user/flutter';
+      Cache.flutterRoot = homePath;
+      for (final String dir in <String>['dev', 'examples', 'packages']) {
+        fileSystem.directory(homePath).childDirectory(dir).createSync(recursive: true);
+      }
+    });
+
+    testUsingContext('SIGABRT throws Exception', () async {
+      const String stderr = 'Something bad happened!';
+      processManager.addCommands(
+        <FakeCommand>[
+          const FakeCommand(
+            // artifact paths are from Artifacts.test() and stable
+            command: <String>[
+              'HostArtifact.engineDartSdkPath/bin/dart',
+              '--disable-dart-dev',
+              'HostArtifact.engineDartSdkPath/bin/snapshots/analysis_server.dart.snapshot',
+              '--disable-server-feature-completion',
+              '--disable-server-feature-search',
+              '--sdk',
+              'HostArtifact.engineDartSdkPath',
+            ],
+            exitCode: SIGABRT,
+            stderr: stderr,
+          ),
+        ],
+      );
+      await expectLater(
+        runner.run(<String>['analyze']),
+        throwsA(
+          isA<Exception>().having(
+            (Exception e) => e.toString(),
+            'description',
+            contains('analysis server exited with code $SIGABRT and output:\n[stderr] $stderr'),
+          ),
+        ),
+      );
+    },
+    overrides: <Type, Generator>{
+      FileSystem: () => fileSystem,
+      ProcessManager: () => processManager,
+    });
+  });
+
   testWithoutContext('analyze inRepo', () {
     final FileSystem fileSystem = MemoryFileSystem.test();
     fileSystem.directory(_kFlutterRoot).createSync(recursive: true);