Improve pub's pubspec error messages.

sdk/lib/_internal/pub/test/pubspec_test.dart

 // Copyright (c) 2012, 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.
 
 library pubspec_test;
 
 import 'dart:async';
 
 import 'package:unittest/unittest.dart';
 
@@ skipping 230 matching lines @@
 
     test("throws if transformers isn't a list", () {
       expectPubspecException('transformers: "not list"',
           (pubspec) => pubspec.transformers,
           '"transformers" field must be a list');
     });
 
     test("throws if a transformer isn't a string or map", () {
       expectPubspecException('transformers: [12]',
           (pubspec) => pubspec.transformers,
-          '"transformers" field must be a string or map');
+          'A transformer must be a string or map.');
     });
 
     test("throws if a transformer's configuration isn't a map", () {
       expectPubspecException('transformers: [{pkg: 12}]',
           (pubspec) => pubspec.transformers,
-          '"transformers.pkg" field must be a map');
+          "A transformer's configuration must be a map.");
     });
 
     test("throws if a transformer's configuration contains an unknown "
         "reserved key at the top level", () {
       expectPubspecException('''
 name: pkg
 transformers: [{pkg: {\$key: "value"}}]''',
           (pubspec) => pubspec.transformers,
-          'Invalid transformer configuration for "transformers.pkg": '
-          'Unknown reserved field "\$key"');
+          'Invalid transformer config: Unknown reserved field.');
     });
 
     test("doesn't throw if a transformer's configuration contains a "
         "non-top-level key beginning with a dollar sign", () {
       var pubspec = new Pubspec.parse('''
 name: pkg
 transformers:
 - pkg: {outer: {\$inner: value}}
 ''', sources);
 
       var pkg = pubspec.transformers[0].single;
       expect(pkg.configuration["outer"]["\$inner"], equals("value"));
     });
 
     test("throws if the \$include value is not a string or list", () {
       expectPubspecException('''
 name: pkg
 transformers:
 - pkg: {\$include: 123}''',
           (pubspec) => pubspec.transformers,
-          'Invalid transformer configuration for "transformers.pkg": '
-          '"\$include" field must be a string or list, but was "123"');
+          'Invalid transformer config: "\$include" field must be a string or '
+            'list.');
     });
 
     test("throws if the \$include list contains a non-string", () {
       expectPubspecException('''
 name: pkg
 transformers:
 - pkg: {\$include: ["ok", 123, "alright", null]}''',
         (pubspec) => pubspec.transformers,
-        'Invalid transformer configuration for "transformers.pkg": '
-        '"\$include" list field may only contain strings, but contained '
-        '"123" and "null"');
+        'Invalid transformer config: "\$include" field may contain only '
+          'strings.');
     });
 
     test("throws if the \$exclude value is not a string or list", () {
       expectPubspecException('''
 name: pkg
 transformers:
 - pkg: {\$exclude: 123}''',
         (pubspec) => pubspec.transformers,
-        'Invalid transformer configuration for "transformers.pkg": '
-        '"\$exclude" field must be a string or list, but was "123"');
+        'Invalid transformer config: "\$exclude" field must be a string or '
+          'list.');
     });
 
     test("throws if the \$exclude list contains a non-string", () {
       expectPubspecException('''
 name: pkg
 transformers:
 - pkg: {\$exclude: ["ok", 123, "alright", null]}''',
         (pubspec) => pubspec.transformers,
-        'Invalid transformer configuration for "transformers.pkg": '
-        '"\$exclude" list field may only contain strings, but contained '
-        '"123" and "null"');
+        'Invalid transformer config: "\$exclude" field may contain only '
+          'strings.');
     });
 
     test("throws if a transformer is not from a dependency", () {
       expectPubspecException('''
 name: pkg
 transformers: [foo]
 ''',
         (pubspec) => pubspec.transformers,
-        '"transformers.foo" refers to a package that\'s not a dependency.');
+        '"foo" is not a dependency.');
     });
 
     test("allows a transformer from a normal dependency", () {
       var pubspec = new Pubspec.parse('''
 name: pkg
 dependencies:
   foo:
     mock: ok
 transformers:
 - foo''', sources);
@@ skipping 70 matching lines @@
             (pubspec) => pubspec.environment);
       });
 
       test("throws if the sdk isn't a valid version constraint", () {
         expectPubspecException('environment: {sdk: "oopies"}',
             (pubspec) => pubspec.environment);
       });
     });
   });
 }