Add support for ^ constraints in pub.

sdk/lib/_internal/pub_generated/test/validator/dependency_test.dart

 // Copyright (c) 2013, 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 'dart:convert';
 
 import 'package:http/http.dart' as http;
 import 'package:http/testing.dart';
 import 'package:path/path.dart' as path;
@@ skipping 41 matching lines @@
   }));
 
   d.dir(appPath, [d.libPubspec("test_pkg", "1.0.0", deps: {
       "foo": dep
     })]).create();
 }
 
 main() {
   initConfig();
 
-  integration('should consider a package valid if it looks normal', () {
-    d.validPackage.create();
-    expectNoValidationError(dependency);
+  group('should consider a package valid if it', () {
+    integration('looks normal', () {
+      d.validPackage.create();
+      expectNoValidationError(dependency);
+    });
+
+    integration('has a ^ constraint with an appropriate SDK constraint', () {
+      d.dir(appPath, [d.libPubspec("test_pkg", "1.0.0", deps: {
+          "foo": "^1.2.3"
+        }, sdk: ">=1.8.0 <2.0.0")]).create();
+      expectNoValidationError(dependency);
+    });
   });
 
   group('should consider a package invalid if it', () {
     setUp(d.validPackage.create);
 
     group('has a git dependency', () {
       group('where a hosted version exists', () {
         integration("and should suggest the hosted primary version", () {
           setUpDependency({
             'git': 'git://github.com/dart-lang/foo'
@@ skipping 298 matching lines @@
       });
 
       integration('and it should preserve the lower-bound operator', () {
         d.dir(appPath, [d.libPubspec("test_pkg", "1.0.0", deps: {
             "foo": ">1.2.3"
           })]).create();
 
         expectDependencyValidationWarning('  foo: ">1.2.3 <2.0.0"');
       });
     });
+
+    group('has a ^ dependency', () {
+      integration("without an SDK constraint", () {
+        d.dir(appPath, [d.libPubspec("integration_pkg", "1.0.0", deps: {
+            "foo": "^1.2.3"
+          })]).create();
+
+        expectDependencyValidationError('  foo: ">=1.2.3 <2.0.0"');
+      });
+
+      integration("with a too-broad SDK constraint", () {
+        d.dir(appPath, [d.libPubspec("test_pkg", "1.0.0", deps: {
+            "foo": "^1.2.3"
+          }, sdk: ">=1.5.0 <2.0.0")]).create();
+
+        expectDependencyValidationError('  foo: ">=1.2.3 <2.0.0"');
+      });
+    });
   });
 }