Pass additional options in incremental setup

pkg/front_end/test/incremental_kernel_generator_test.dart

 // Copyright (c) 2017, 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.
 
 import 'dart:async';
 
 import 'package:front_end/compiler_options.dart';
 import 'package:front_end/incremental_kernel_generator.dart';
 import 'package:front_end/memory_file_system.dart';
 import 'package:front_end/src/incremental/byte_store.dart';
@@ skipping 16 matching lines @@
   /// Virtual filesystem for testing.
   final fileSystem = new MemoryFileSystem(Uri.parse('file:///'));
 
   /// The used file watcher.
   WatchUsedFilesFn watchFn = (uri, used) {};
 
   /// The object under test.
   IncrementalKernelGeneratorImpl incrementalKernelGenerator;
 
   /// Compute the initial [Program] for the given [entryPoint].
-  Future<Program> getInitialState(Uri entryPoint) async {
+  Future<Program> getInitialState(Uri entryPoint,
+      {bool setPackages: true}) async {
     Map<String, Uri> dartLibraries = createSdkFiles(fileSystem);
     // TODO(scheglov) Builder the SDK kernel and set it into the options.
 
     // TODO(scheglov) Make `.packages` file optional.
 
     var compilerOptions = new CompilerOptions()
       ..fileSystem = fileSystem
       ..byteStore = new MemoryByteStore()
 //      ..logger = new PerformanceLog(stdout)
       ..strongMode = true
       ..chaseDependencies = true
-      ..dartLibraries = dartLibraries
-      ..packagesFileUri = Uri.parse('file:///test/.packages');
+      ..dartLibraries = dartLibraries;
+
+    if (setPackages) {
+      compilerOptions.packagesFileUri = Uri.parse('file:///test/.packages');
+    }
     incrementalKernelGenerator = await IncrementalKernelGenerator
         .newInstance(compilerOptions, entryPoint, watch: watchFn);
     return (await incrementalKernelGenerator.computeDelta()).newProgram;
   }
 
   test_compile_chain() async {
     writeFile('/test/.packages', 'test:lib/');
     String aPath = '/test/lib/a.dart';
     String bPath = '/test/lib/b.dart';
     String cPath = '/test/lib/c.dart';
@@ skipping 162 matching lines @@
 import self as self;
 import "dart:core" as core;
 
 static method main() → dynamic {
   core::double v = 2.3;
 }
 ''');
     }
   }
 
+  test_inferPackagesFile() async {
+    writeFile('/test/.packages', 'test:lib/');
+    String aPath = '/test/lib/a.dart';
+    String bPath = '/test/lib/b.dart';
+    writeFile(aPath, 'var a = 1;');
+    Uri bUri = writeFile(bPath, r'''
+import "package:test/a.dart";
+var b = a;
+''');
+
+    // Ensures that the `.packages` file can be discovered automatically
+    // from the entry point file.
+    Program program = await getInitialState(bUri, setPackages: false);
+    Library library = _getLibrary(program, bUri);
+    expect(_getLibraryText(library), r'''
+library;
+import self as self;
+import "dart:core" as core;
+import "package:test/a.dart" as a;
+
+static field core::int b = a::a;
+''');
+  }
+
   test_watch() async {
     writeFile('/test/.packages', 'test:lib/');
     String aPath = '/test/lib/a.dart';
     String bPath = '/test/lib/b.dart';
     String cPath = '/test/lib/c.dart';
     Uri aUri = writeFile(aPath, '');
     Uri bUri = writeFile(bPath, '');
     Uri cUri = writeFile(cPath, r'''
 import 'a.dart';
 ''');
@@ skipping 109 matching lines @@
     throw fail('No library found with URI "$uri"');
   }
 
   String _getLibraryText(Library library) {
     StringBuffer buffer = new StringBuffer();
     new Printer(buffer, syntheticNames: new NameSystem())
         .writeLibraryFile(library);
     return buffer.toString();
   }
 }