Work in progress: front end hot reload API

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:analyzer/file_system/physical_file_system.dart';
+import 'package:analyzer/src/dart/sdk/sdk.dart';
+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:kernel/ast.dart';
+import 'package:path/path.dart' as pathos;
+import 'package:test/test.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';
+
+main() {
+  defineReflectiveSuite(() {
+    defineReflectiveTests(IncrementalKernelGeneratorTest);
+  });
+}
+
+final _sdkSummary = _readSdkSummary();
+
+List<int> _readSdkSummary() {
+  var resourceProvider = PhysicalResourceProvider.INSTANCE;
+  var sdk = new FolderBasedDartSdk(resourceProvider,
+      FolderBasedDartSdk.defaultSdkDirectory(resourceProvider))
+    ..useSummary = true;
+  var path = resourceProvider.pathContext
+      .join(sdk.directory.path, 'lib', '_internal', 'strong.sum');
+  return resourceProvider.getFile(path).readAsBytesSync();
+}
+
+@reflectiveTest
+class IncrementalKernelGeneratorTest {
+  static final sdkSummaryUri = Uri.parse('special:sdk_summary');
+
+  /// Virtual filesystem for testing.
+  final fileSystem = new MemoryFileSystem(pathos.posix, Uri.parse('file:///'));
+
+  /// The object under test.
+  IncrementalKernelGenerator incrementalKernelGenerator;
+
+  Future<Map<Uri, Program>> getInitialState(Uri startingUri) async {
+    fileSystem.entityForUri(sdkSummaryUri).writeAsBytesSync(_sdkSummary);
+    incrementalKernelGenerator = new IncrementalKernelGenerator(
+        startingUri,
+        new CompilerOptions()
+          ..fileSystem = fileSystem
+          ..chaseDependencies = true
+          ..sdkSummary = sdkSummaryUri
+          ..packagesFileUri = new Uri());
+    return (await incrementalKernelGenerator.computeDelta()).newState;
+  }
+
+  test_emptyProgram() async {
+    writeFiles({'/foo.dart': 'main() {}'});
+    var fileUri = Uri.parse('file:///foo.dart');
+    var initialState = await getInitialState(fileUri);
+    expect(initialState.keys, unorderedEquals([fileUri]));
+    var program = initialState[fileUri];
+    expect(program.libraries, hasLength(1));
+    var library = program.libraries[0];
+    expect(library.importUri, fileUri);
+    expect(library.classes, isEmpty);
+    expect(library.procedures, hasLength(1));
+    expect(library.procedures[0].name.name, 'main');
+    var body = library.procedures[0].function.body;
+    expect(body, new isInstanceOf<Block>());
+    var block = body as Block;
+    expect(block.statements, isEmpty);
+  }
+
+  /// Write the given file contents to the virtual filesystem.
+  void writeFiles(Map<String, String> contents) {
+    contents.forEach((path, text) {
+      fileSystem
+          .entityForUri(Uri.parse('file://$path'))
+          .writeAsStringSync(text);
+    });
+  }
+}