Add support for Flutter SDK constraints.

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.
 
 import 'package:pub/src/package.dart';
 import 'package:pub/src/pubspec.dart';
 import 'package:pub/src/source.dart';
 import 'package:pub/src/source/path.dart';
 import 'package:pub/src/source_registry.dart';
 import 'package:pub/src/system_cache.dart';
@@ skipping 387 matching lines @@
       expectPubspecException('''
 name: pkg
 dependencies:
   from_path: {path: non_local_path}
 ''', (pubspec) => pubspec.dependencies,
           '"non_local_path" is a relative path, but this isn\'t a local '
           'pubspec.');
     });
 
     group("environment", () {
-      test("defaults to any SDK constraint if environment is omitted", () {
+      test("allows an omitted environment", () {
         var pubspec = new Pubspec.parse('', sources);
-        expect(pubspec.environment.sdkVersion, equals(VersionConstraint.any));
-      });
-
-      test("allows an empty environment map", () {
-        var pubspec = new Pubspec.parse('''
-environment:
-''', sources);
-        expect(pubspec.environment.sdkVersion, equals(VersionConstraint.any));
+        expect(pubspec.dartSdkConstraint, equals(VersionConstraint.any));
+        expect(pubspec.flutterSdkConstraint, isNull);
       });
 
       test("throws if the environment value isn't a map", () {
         expectPubspecException('environment: []',
-            (pubspec) => pubspec.environment);
+            (pubspec) => pubspec.dartSdkConstraint);
       });
 
-      test("allows a version constraint for the sdk", () {
+      test("allows a version constraint for the SDKs", () {
         var pubspec = new Pubspec.parse('''
 environment:
   sdk: ">=1.2.3 <2.3.4"
+  flutter: ^0.1.2
 ''', sources);
-        expect(pubspec.environment.sdkVersion,
+        expect(pubspec.dartSdkConstraint,
             equals(new VersionConstraint.parse(">=1.2.3 <2.3.4")));
+        expect(pubspec.flutterSdkConstraint,
+            equals(new VersionConstraint.parse("^0.1.2")));
       });
 
       test("throws if the sdk isn't a string", () {
         expectPubspecException('environment: {sdk: []}',
-            (pubspec) => pubspec.environment);
+            (pubspec) => pubspec.dartSdkConstraint);
         expectPubspecException('environment: {sdk: 1.0}',
-            (pubspec) => pubspec.environment);
+            (pubspec) => pubspec.dartSdkConstraint);
+        expectPubspecException('environment: {sdk: 1.2.3, flutter: []}',
+            (pubspec) => pubspec.dartSdkConstraint);
+        expectPubspecException('environment: {sdk: 1.2.3, flutter: 1.0}',
+            (pubspec) => pubspec.dartSdkConstraint);
       });
 
       test("throws if the sdk isn't a valid version constraint", () {
         expectPubspecException('environment: {sdk: "oopies"}',
-            (pubspec) => pubspec.environment);
+            (pubspec) => pubspec.dartSdkConstraint);
+        expectPubspecException('environment: {sdk: 1.2.3, flutter: "oopies"}',
+            (pubspec) => pubspec.dartSdkConstraint);
       });
     });
 
     group("publishTo", () {
       test("defaults to null if omitted", () {
         var pubspec = new Pubspec.parse('', sources);
         expect(pubspec.publishTo, isNull);
       });
 
       test("throws if not a string", () {
@@ skipping 68 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'));
       });
     });
   });
 }