Fix computing export scopes for library cycles and after loading.

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 127 matching lines @@
         _getLibraryText(library),
         r'''
 library;
 import self as self;
 import "./a.dart" as a;
 
 static field a::A a;
 ''');
   }
 
+  test_compile_export_cycle() async {
+    writeFile('/test/.packages', 'test:lib/');
+    String aPath = '/test/lib/a.dart';
+    String bPath = '/test/lib/b.dart';
+    String cPath = '/test/lib/c.dart';
+    writeFile(aPath, 'export "b.dart"; class A {}');
+    writeFile(bPath, 'export "a.dart"; class B {}');
+    Uri cUri = writeFile(
+        cPath,
+        r'''
+import 'b.dart';
+A a;
+B b;
+''');
+
+    {
+      Program program = await getInitialState(cUri);
+      Library library = _getLibrary(program, cUri);
+      expect(
+          _getLibraryText(library),
+          r'''
+library;
+import self as self;
+import "./a.dart" as a;
+import "./b.dart" as b;
+
+static field a::A a;
+static field b::B b;
+''');
+    }
+
+    // Update c.dart and compile.
+    // We should load the cycle [a.dart, b.dart] from the byte store.
+    // This tests that we compute export scopes after loading.
+    writeFile(
+        cPath,
+        r'''
+import 'b.dart';
+A a;
+B b;
+int c;
+''');
+    incrementalKernelGenerator.invalidate(cUri);
+    {
+      DeltaProgram delta = await incrementalKernelGenerator.computeDelta();
+      Program program = delta.newProgram;
+      Library library = _getLibrary(program, cUri);
+      expect(
+          _getLibraryText(library),
+          r'''
+library;
+import self as self;
+import "./a.dart" as a;
+import "./b.dart" as b;
+import "dart:core" as core;
+
+static field a::A a;
+static field b::B b;
+static field core::int c;
+''');
+    }
+  }
+
   test_compile_typedef() async {
     writeFile('/test/.packages', 'test:lib/');
     String aPath = '/test/lib/a.dart';
     String bPath = '/test/lib/b.dart';
     writeFile(aPath, 'typedef int F<T>(T x);');
     Uri bUri = writeFile(
         bPath,
         r'''
 import 'a.dart';
 F<String> f;
@@ skipping 203 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();
   }
 }