Correctly set root_library based on the application script URI instead of looking for the library t…

utils/kernel-service/kernel-service.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /// This is an interface to the Dart Kernel parser and Kernel binary generator.
 ///
 /// It is used by the kernel-isolate to load Dart source code and generate
 /// Kernel binary format.
 ///
 /// This is either invoked as the root script of the Kernel isolate when used
@@ skipping 30 matching lines @@
 // Process a request from the runtime. See KernelIsolate::CompileToKernel in
 // kernel_isolate.cc and Loader::SendKernelRequest in loader.cc.
 Future _processLoadRequest(request) async {
   if (verbose) print("DFE: request: $request");
 
   int tag = request[0];
   final SendPort port = request[1];
   final String inputFileUri = request[2];
   final Uri script = Uri.base.resolve(inputFileUri);
 
-  FileSystem fileSystem = request.length > 3
-      ? _buildFileSystem(request[3])
-      : PhysicalFileSystem.instance;
+  FileSystem fileSystem = PhysicalFileSystem.instance;
+  bool requireMain = true;
+
+  if (request.length > 3) {
+    fileSystem = _buildFileSystem(request[3]);
+    requireMain = false;
+  }
 
   Uri packagesUri = (Platform.packageConfig != null)
       ? Uri.parse(Platform.packageConfig)
       : null;
 
   Uri sdkSummary = Uri.base
       .resolveUri(new Uri.file(Platform.resolvedExecutable))
       .resolveUri(new Uri.directory("patched_sdk"))
       // TODO(sigmund): use outline.dill when the mixin transformer is modular.
       .resolve('platform.dill');
@@ skipping 11 matching lines @@
     ..strongMode = strongMode
     ..fileSystem = fileSystem
     ..target = new VmFastaTarget(new TargetFlags(strongMode: strongMode))
     ..packagesFileUri = packagesUri
     ..sdkSummary = sdkSummary
     ..verbose = verbose
     ..onError = (CompilationError e) => errors.add(e.message);
 
   CompilationResult result;
   try {
-    Program program = await kernelForProgram(script, options);
+    Program program = requireMain
+        ? await kernelForProgram(script, options)
+        : await kernelForBuildUnit([script], options..chaseDependencies = true);
+
     if (errors.isNotEmpty) {
       result = new CompilationResult.errors(errors);
     } else {
       // We serialize the program excluding 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
       // decide what to excluce.
       // TODO(sigmund): remove the following line (Issue #30111)
       program.libraries.forEach((e) => e.isExternal = false);
       result = new CompilationResult.ok(
@@ skipping 145 matching lines @@
   _CompilationCrash(this.exception, this.stack);
 
   @override
   Status get status => Status.crash;
 
   @override
   String get errorString => "${exception}\n${stack}";
 
   String toString() => "_CompilationCrash(${errorString})";
 }