Use messages for (some) public API errors

pkg/front_end/test/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 'package:front_end/front_end.dart';
 import 'package:front_end/src/fasta/kernel/utils.dart';
 import 'package:front_end/src/testing/compiler_common.dart';
 import 'package:kernel/ast.dart';
 
 import 'package:test/test.dart';
@@ skipping 38 matching lines @@
 
       // Note: summaries created by the SDK today contain empty statements as
       // method bodies.
       expect(printMember.function.body is EmptyStatement, isTrue);
     });
 
     test('compiler requires a main method', () async {
       var errors = [];
       var options = new CompilerOptions()..onError = (e) => errors.add(e);
       await compileScript('a() => print("hi");', options: options);
-      expect('${errors.first}', contains("No 'main' method found"));
+      // TODO(sigmund): when we expose codes in the public APIs, we should
+      // compare the code here and not the message.
+      expect(errors.first.message, contains("No 'main' method found"));

[ahe, 2017/07/12 13:14:44]

Since this is a front_end test, you can import fasta_codes.dart and compare the
codes now.

[Siggi Cherem (dart-lang), 2017/07/12 21:54:59]

Not quite: we are not exposing the `Code` class from the public API. We should
expose something in the future, but we can deal with that separately.

     });
 
     test('default error handler throws', () async {
       var exceptionThrown = false;
       try {
         await compileScript('a() => print("hi");');
-      } catch (e) {
+      } on CompilationError catch (e) {
         exceptionThrown = true;
-        expect('$e', contains("No 'main' method found"));
+        expect(e.message, contains("No 'main' method found"));
       }
       expect(exceptionThrown, isTrue);
     });
 
     test('generated program contains source-info', () async {
       var program = await compileScript('a() => print("hi"); main() {}',
           fileName: 'a.dart');
       // Kernel always store an empty '' key in the map, so there is always at
       // least one. Having more means that source-info is added.
       expect(program.uriToSource.keys.length, greaterThan(1));
@@ skipping 60 matching lines @@
     });
 
     test('compiler by default is hermetic', () async {
       var errors = [];
       var options = new CompilerOptions()..onError = (e) => errors.add(e);
       var sources = {
         'a.dart': 'import "b.dart"; a() => print("hi");',
         'b.dart': ''
       };
       await compileUnit(['a.dart'], sources, options: options);
-      expect(errors.first.toString(), contains('Invalid access'));
+      expect(errors.first.message, contains('Invalid access'));
       errors.clear();
 
       await compileUnit(['a.dart', 'b.dart'], sources, options: options);
       expect(errors, isEmpty);
     });
 
     test('chaseDependencies=true removes hermetic restriction', () async {
       var errors = [];
       var options = new CompilerOptions()
         ..chaseDependencies = true
@@ skipping 41 matching lines @@
       checkDCallsC(unitD1);
 
       var unitD2 = await compileUnit(['d.dart'], sources,
           inputSummaries: ['bc.dill', 'a.dill']);
       checkDCallsC(unitD2);
     });
 
     // TODO(sigmund): add tests with trimming dependencies
   });
 }