[VM] Use the incremental compiler to compile sources only when the observatory

server is started.

When the incremental compiler is used it accumulates state that
increases the footprint of the process. This state is needed only
when the 'reload' or 'expression evaluation' functionality is used
in the debugger.

Currently in the VM we do not have a good way of detecting when the
debugger will be used as the vm service observatory functionality
can be turned on dynamically after the program has started.

This CL turns on the incremental compiler only when command line options
are used to start the observatory server. We could run into issues with
'expression evaluation' when the observatory is started dynamically after
the program is loaded.

Change-Id: I18c17698622071bca428018f7fdac1a84b0f195e
Reviewed-on: https://dart-review.googlesource.com/64667
Reviewed-by: Ryan Macnak <[email protected]>
Commit-Queue: Siva Annamalai <[email protected]>

Author: a-siva

pkg/vm/bin/kernel_service.dart

@@ -305,18 +305,20 @@ void _recordDependencies(
     int isolateId, Component component, String packageConfig) {
   final dependencies = isolateDependencies[isolateId] ??= new List<Uri>();
 
-  for (var lib in component.libraries) {
-    if (lib.importUri.scheme == "dart") continue;
-
-    dependencies.add(lib.fileUri);
-    for (var part in lib.parts) {
-      final fileUri = lib.fileUri.resolve(part.partUri);
-      if (fileUri.scheme != "" && fileUri.scheme != "file") {
-        // E.g. part 'package:foo/foo.dart';
-        // Maybe the front end should resolve this?
-        continue;
+  if (component != null) {
+    for (var lib in component.libraries) {
+      if (lib.importUri.scheme == "dart") continue;
+
+      dependencies.add(lib.fileUri);
+      for (var part in lib.parts) {
+        final fileUri = lib.fileUri.resolve(part.partUri);
+        if (fileUri.scheme != "" && fileUri.scheme != "file") {
+          // E.g. part 'package:foo/foo.dart';
+          // Maybe the front end should resolve this?
+          continue;
+        }
+        dependencies.add(fileUri);
       }
-      dependencies.add(fileUri);
     }
   }
 
@@ -447,7 +449,7 @@ Future _processLoadRequest(request) async {
     FileSystem fileSystem = _buildFileSystem(
         sourceFiles, platformKernel, multirootFilepaths, multirootScheme);
     compiler = new SingleShotCompilerWrapper(fileSystem, platformKernelPath,
-        requireMain: sourceFiles.isEmpty,
+        requireMain: false,
         strongMode: strong,
         suppressWarnings: suppressWarnings,
         syncAsync: syncAsync,
@@ -461,12 +463,17 @@ Future _processLoadRequest(request) async {
     }
 
     Component component = await compiler.compile(script);
-    _recordDependencies(isolateId, component, packageConfig);
 
     if (compiler.errors.isNotEmpty) {
-      result = new CompilationResult.errors(compiler.errors,
-          serializeComponent(component, filter: (lib) => !lib.isExternal));
+      if (component != null) {
+        result = new CompilationResult.errors(compiler.errors,
+            serializeComponent(component, filter: (lib) => !lib.isExternal));
+      } else {
+        result = new CompilationResult.errors(compiler.errors, null);
+      }
     } else {
+      // Record dependencies only if compilation was error free.
+      _recordDependencies(isolateId, component, packageConfig);
       // We serialize the component excluding vm_platform.dill because the VM has
       // these sources built-in. Everything loaded as a summary in
       // [kernelForProgram] is marked `external`, so we can use that bit to

runtime/bin/dfe.cc

@@ -81,6 +81,7 @@ static char* GetDirectoryPrefixFromExeName() {
 
 DFE::DFE()
     : use_dfe_(false),
+      use_incremental_compiler_(false),
       frontend_filename_(NULL),
       application_kernel_buffer_(NULL),
       application_kernel_buffer_size_(0) {}
@@ -218,8 +219,8 @@ void DFE::CompileAndReadScript(const char* script_uri,
                                int* exit_code,
                                bool strong,
                                const char* package_config) {
-  Dart_KernelCompilationResult result =
-      CompileScript(script_uri, strong, true, package_config);
+  Dart_KernelCompilationResult result = CompileScript(
+      script_uri, strong, use_incremental_compiler(), package_config);
   switch (result.status) {
     case Dart_KernelCompilationStatus_Ok:
       *kernel_buffer = result.kernel;

runtime/bin/dfe.h

@@ -34,6 +34,11 @@ class DFE {
   void set_use_dfe(bool value = true) { use_dfe_ = value; }
   bool UseDartFrontend() const { return use_dfe_; }
 
+  void set_use_incremental_compiler(bool value) {
+    use_incremental_compiler_ = value;
+  }
+  bool use_incremental_compiler() const { return use_incremental_compiler_; }
+
   // Returns the platform binary file name if the path to
   // kernel binaries was set using SetKernelBinaries.
   const char* GetPlatformBinaryFilename();
@@ -100,6 +105,7 @@ class DFE {
 
  private:
   bool use_dfe_;
+  bool use_incremental_compiler_;
   char* frontend_filename_;
 
   // Kernel binary specified on the cmd line.

runtime/bin/main_options.cc

@@ -296,6 +296,9 @@ bool Options::ProcessEnableVmServiceOption(const char* arg,
         "Use --enable-vm-service[=<port number>[/<bind address>]]\n");
     return false;
   }
+#if !defined(DART_PRECOMPILED_RUNTIME)
+  dfe()->set_use_incremental_compiler(true);
+#endif  // !defined(DART_PRECOMPILED_RUNTIME)
 
   return true;
 }
@@ -320,6 +323,9 @@ bool Options::ProcessObserveOption(const char* arg,
   vm_options->AddArgument("--pause-isolates-on-unhandled-exceptions");
   vm_options->AddArgument("--profiler");
   vm_options->AddArgument("--warn-on-pause-with-no-debugger");
+#if !defined(DART_PRECOMPILED_RUNTIME)
+  dfe()->set_use_incremental_compiler(true);
+#endif  // !defined(DART_PRECOMPILED_RUNTIME)
   return true;
 }
 

tests/lib_2/mirrors/dynamic_load_test.dart

@@ -43,6 +43,7 @@ main() async {
   }
   print(error);
   Expect.isTrue(error.toString().contains("Cannot open file") ||
+      error.toString().contains("file not found") ||
       error.toString().contains("No such file or directory") ||
       error.toString().contains("The system cannot find the file specified"));
   Expect.isTrue(error.toString().contains("DOES_NOT_EXIST"));

tests/standalone_2/standalone_2_kernel.status

@@ -203,5 +203,8 @@ package/package_isolate_test: CompileTimeError
 [ $fasta && !$strong ]
 regress_29350_test/none: MissingCompileTimeError
 
+[ $strong && ($compiler == dartk || $compiler == dartkp) ]
+io/named_pipe_script_test: RuntimeError # Issue 33842
+
 [ !$strong && ($compiler == dartk || $compiler == dartkp || $runtime == dart_precompiled || $runtime == vm) ]
 *: SkipByDesign # standalone_2 is only supported in strong mode.