Printing a useful error message if a version field is a num

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

 library pubspec_test;
 import 'dart:async';
 import 'package:pub_semver/pub_semver.dart';
 import 'package:unittest/unittest.dart';
 import '../lib/src/package.dart';
 import '../lib/src/pubspec.dart';
 import '../lib/src/source.dart';
 import '../lib/src/source_registry.dart';
 import 'test_pub.dart';
 class MockSource extends Source {
@@ skipping 176 matching lines @@
     mock: ok
     version: not constraint
 ''', (pubspec) => pubspec.dependencies);
     });
     test("throws if 'name' is not a string", () {
       expectPubspecException(
           'name: [not, a, string]',
           (pubspec) => pubspec.name);
     });
     test("throws if version is not a string", () {
-      expectPubspecException('version: 1.0', (pubspec) => pubspec.version);
+      expectPubspecException('version: [2, 0, 0]',
+          (pubspec) => pubspec.version,
+          '"version" field must be a string');
+    });
+    test("throws if version is malformed (looking like a double)", () {
+      expectPubspecException('version: 2.1',
+          (pubspec) => pubspec.version,
+          '"version" field must have three numeric components: major, minor, '
+          'and patch. Instead of "2.1", consider "2.1.0"');
+    });
+    test("throws if version is malformed (looking like an int)", () {
+      expectPubspecException('version: 2',
+          (pubspec) => pubspec.version,
+          '"version" field must have three numeric components: major, minor, '
+          'and patch. Instead of "2", consider "2.0.0"');
     });
     test("throws if version is not a version", () {
       expectPubspecException(
           'version: not version',
           (pubspec) => pubspec.version);
     });
     test("throws if transformers isn't a list", () {
       expectPubspecException(
           'transformers: "not list"',
           (pubspec) => pubspec.transformers,
@@ skipping 223 matching lines @@
       test("uses the key if the value is null", () {
         var pubspec = new Pubspec.parse('''
 executables:
   command:
 ''', sources);
         expect(pubspec.executables['command'], equals('command'));
       });
     });
   });
 }