[ VM Service ] Add support for '--[no-]serve-observatory'

To prepare for the eventual removal of Observatory, we plan on disabling
Observatory by default while providing an escape hatch to manually serve
the tool for some period of time before completely removing Observatory
from the SDK. This change adds flags that can be used to configure
whether or not Observatory is served.

Currently, '--serve-observatory' is the default behavior, but will be
changed to '--no-serve-observatory' once tooling is ready to support the
escape hatch behavior.

Part of #50233

TEST=run_test.dart

Change-Id: Ib6d1e1587d9fbd3c61d4a4c75d90635052835844
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/267720
Reviewed-by: Siva Annamalai <asiva@google.com>
Commit-Queue: Ben Konyi <bkonyi@google.com>

pkg/dartdev/lib/src/commands/run.dart

@@ -212,6 +212,10 @@ class RunCommand extends DartdevCommand {
                 'functionality. Note: Disabling DDS may break some '
                 'functionality in IDEs and other tooling.',
             defaultsTo: true)
+        ..addFlag('serve-observatory',
+            hide: !verbose,
+            help: 'Enable hosting Observatory through the VM Service.',
+            defaultsTo: true)
         ..addFlag(
           'debug-dds',
           hide: true,

pkg/dartdev/test/commands/run_test.dart

@@ -18,6 +18,8 @@ const devToolsMessagePrefix =
     'The Dart DevTools debugger and profiler is available at: http://127.0.0.1:';
 const dartVMServiceMessagePrefix =
     'The Dart VM service is listening on http://127.0.0.1:';
+final dartVMServiceRegExp =
+    RegExp(r'The Dart VM service is listening on (http://127.0.0.1:.*)');
 const residentFrontendServerPrefix =
     'The Resident Frontend Compiler is listening at 127.0.0.1:';
 
@@ -577,6 +579,82 @@ void main(List<String> args) => print("$b $args");
       skip: Platform.isWindows,
     );
   });
+
+  group('Observatory', () {
+    void generateServedTest({
+      required bool serve,
+      required bool enableAuthCodes,
+      required bool explicitRun,
+      required bool withDds,
+    }) {
+      test(
+        '${serve ? 'served by default' : 'not served'} ${enableAuthCodes ? "with" : "without"} '
+        'auth codes, ${explicitRun ? 'explicit' : 'implicit'} run,${withDds ? ' ' : 'no'} DDS',
+        () async {
+          p = project(
+            mainSrc:
+                'void main() { print("ready"); int i = 0; while(true) { i++; } }',
+          );
+          Process process = await p.start([
+            if (explicitRun) 'run',
+            '--enable-vm-service',
+            if (!withDds) '--no-dds',
+            if (!enableAuthCodes) '--disable-service-auth-codes',
+            if (!serve) '--no-serve-observatory',
+            p.relativeFilePath,
+          ]);
+
+          final completer = Completer<void>();
+
+          late StreamSubscription sub;
+          late String uri;
+          sub = process.stdout.transform(utf8.decoder).listen((event) async {
+            if (event.contains(dartVMServiceRegExp)) {
+              uri = dartVMServiceRegExp.firstMatch(event)!.group(1)!;
+              await sub.cancel();
+              completer.complete();
+            }
+          });
+          // Wait for process to start.
+          await completer.future;
+          final client = HttpClient();
+          final request = await client.getUrl(Uri.parse(uri));
+          final response = await request.close();
+          final content = await response.transform(utf8.decoder).join();
+          expect(content.contains('Dart VM Observatory'), serve);
+          if (!serve) {
+            if (withDds) {
+              expect(content.contains('DevTools'), true);
+            } else {
+              expect(
+                content,
+                'This VM does not have a registered Dart '
+                'Development Service (DDS) instance and is not currently serving '
+                'Dart DevTools.',
+              );
+            }
+          }
+          process.kill();
+        },
+      );
+    }
+
+    const flags = <bool>[true, false];
+    for (final serve in flags) {
+      for (final enableAuthCodes in flags) {
+        for (final explicitRun in flags) {
+          for (final withDds in flags) {
+            generateServedTest(
+              serve: serve,
+              enableAuthCodes: enableAuthCodes,
+              explicitRun: explicitRun,
+              withDds: withDds,
+            );
+          }
+        }
+      }
+    }
+  });
 }
 
 void residentRun() {

runtime/bin/dart_embedder_api_impl.cc

@@ -108,7 +108,8 @@ Dart_Isolate CreateVmServiceIsolate(const IsolateCreationData& data,
                              config.write_service_info_filename,
                              /*trace_loading=*/false, config.deterministic,
                              /*enable_service_port_fallback=*/false,
-                             /*wait_for_dds_to_advertise_service=*/false)) {
+                             /*wait_for_dds_to_advertise_service=*/false,
+                             /*serve_observatory=*/true)) {
     *error = Utils::StrDup(bin::VmService::GetErrorMessage());
     return nullptr;
   }
@@ -144,7 +145,8 @@ Dart_Isolate CreateVmServiceIsolateFromKernel(
                              config.write_service_info_filename,
                              /*trace_loading=*/false, config.deterministic,
                              /*enable_service_port_fallback=*/false,
-                             /*wait_for_dds_to_advertise_service=*/false)) {
+                             /*wait_for_dds_to_advertise_service=*/false,
+                             /*serve_observatory*/ true)) {
     *error = Utils::StrDup(bin::VmService::GetErrorMessage());
     return nullptr;
   }

runtime/bin/main.cc

@@ -555,7 +555,7 @@ static Dart_Isolate CreateAndSetupServiceIsolate(const char* script_uri,
           Options::vm_service_auth_disabled(),
           Options::vm_write_service_info_filename(), Options::trace_loading(),
           Options::deterministic(), Options::enable_service_port_fallback(),
-          wait_for_dds_to_advertise_service)) {
+          wait_for_dds_to_advertise_service, !Options::disable_observatory())) {
     *error = Utils::StrDup(VmService::GetErrorMessage());
     return NULL;
   }

runtime/bin/main_options.cc

@@ -483,6 +483,11 @@ bool Options::ParseArguments(int argc,
         // a VM flag as disabling DDS changes how we configure the VM service,
         // so we don't need to handle that case here.
         skipVmOption = true;
+      } else if (IsOption(argv[i], "serve-observatory")) {
+        // This flag is currently set by default in vmservice_io.dart, so we
+        // ignore it. --no-serve-observatory is a VM flag so we don't need to
+        // handle that case here.
+        skipVmOption = true;
       }
       if (!skipVmOption) {
         temp_vm_options.AddArgument(argv[i]);

runtime/bin/main_options.h

@@ -48,7 +48,8 @@ namespace bin {
   V(long_ssl_cert_evaluation, long_ssl_cert_evaluation)                        \
   V(bypass_trusting_system_roots, bypass_trusting_system_roots)                \
   V(delayed_filewatch_callback, delayed_filewatch_callback)                    \
-  V(mark_main_isolate_as_system_isolate, mark_main_isolate_as_system_isolate)
+  V(mark_main_isolate_as_system_isolate, mark_main_isolate_as_system_isolate)  \
+  V(no_serve_observatory, disable_observatory)
 
 // Boolean flags that have a short form.
 #define SHORT_BOOL_OPTIONS_LIST(V)                                             \

runtime/bin/run_vm_tests.cc

@@ -151,7 +151,8 @@ static Dart_Isolate CreateAndSetupServiceIsolate(const char* script_uri,
                              /*write_service_info_filename*/ "",
                              /*trace_loading=*/false, /*deterministic=*/true,
                              /*enable_service_port_fallback=*/false,
-                             /*wait_for_dds_to_advertise_service*/ false)) {
+                             /*wait_for_dds_to_advertise_service*/ false,
+                             /*serve_observatory*/ true)) {
     *error = Utils::StrDup(bin::VmService::GetErrorMessage());
     return nullptr;
   }

runtime/bin/vmservice_impl.cc

@@ -119,7 +119,8 @@ bool VmService::Setup(const char* server_ip,
                       bool trace_loading,
                       bool deterministic,
                       bool enable_service_port_fallback,
-                      bool wait_for_dds_to_advertise_service) {
+                      bool wait_for_dds_to_advertise_service,
+                      bool serve_observatory) {
   Dart_Isolate isolate = Dart_CurrentIsolate();
   ASSERT(isolate != NULL);
   SetServerAddress("");
@@ -196,6 +197,10 @@ bool VmService::Setup(const char* server_ip,
                          Dart_NewBoolean(wait_for_dds_to_advertise_service));
   SHUTDOWN_ON_ERROR(result);
 
+  result = Dart_SetField(library, DartUtils::NewString("_serveObservatory"),
+                         serve_observatory ? Dart_True() : Dart_False());
+  SHUTDOWN_ON_ERROR(result);
+
 // Are we running on Windows?
 #if defined(DART_HOST_OS_WINDOWS)
   Dart_Handle is_windows = Dart_True();

runtime/bin/vmservice_impl.h

@@ -22,7 +22,8 @@ class VmService {
                     bool trace_loading,
                     bool deterministic,
                     bool enable_service_port_fallback,
-                    bool wait_for_dds_to_advertise_service);
+                    bool wait_for_dds_to_advertise_service,
+                    bool serve_observatory);
 
   static void SetNativeResolver();
 

sdk/lib/_internal/vm/bin/vmservice_io.dart

@@ -39,6 +39,8 @@ StreamSubscription<ProcessSignal>? _signalSubscription;
 bool _enableServicePortFallback = false;
 @pragma("vm:entry-point")
 bool _waitForDdsToAdvertiseService = false;
+@pragma("vm:entry-point")
+bool _serveObservatory = true;
 
 // HTTP server.
 Server? server;

sdk/lib/_internal/vm/bin/vmservice_server.dart

@@ -369,7 +369,43 @@ class Server {
       }
       return;
     }
-
+    if (!_serveObservatory) {
+      final ddsUri = _service.ddsUri;
+      if (ddsUri == null) {
+        request.response.headers.contentType = ContentType.text;
+        request.response.write('This VM does not have a registered Dart '
+            'Development Service (DDS) instance and is not currently serving '
+            'Dart DevTools.');
+        request.response.close();
+        return;
+      }
+      // We build this path manually rather than manipulating ddsUri directly
+      // as the resulting path requires an unencoded '#'. The Uri class will
+      // always encode '#' as '%23' in paths to avoid conflicts with fragments,
+      // which will result in the redirect failing.
+      final path = StringBuffer();
+      // Add authentication code to the path.
+      if (ddsUri.pathSegments.length > 1) {
+        path.writeAll([
+          ddsUri.pathSegments
+              .sublist(0, ddsUri.pathSegments.length - 1)
+              .join('/'),
+          '/',
+        ]);
+      }
+      final queryComponent = Uri.encodeQueryComponent(
+        ddsUri.replace(scheme: 'ws', path: '${path}ws').toString(),
+      );
+      path.writeAll([
+        'devtools/#/',
+        '?uri=$queryComponent',
+      ]);
+      final redirectUri = Uri.parse(
+        'http://${ddsUri.host}:${ddsUri.port}/$path',
+      );
+      request.response.redirect(redirectUri);
+      return;
+    }
     if (assets == null) {
       request.response.headers.contentType = ContentType.text;
       request.response.write('This VM was built without the Observatory UI.');