Add support for Flutter SDK constraints.

test/must_pub_get_test.dart

 // Copyright (c) 2015, 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:io';
 
 import 'package:path/path.dart' as p;
 import 'package:pub/src/exit_codes.dart' as exit_codes;
 import 'package:pub/src/io.dart';
@@ skipping 268 matching lines @@
           d.appPubspec({"foo": "3.0.0"})
         ]).create();
 
         pubGet(environment: {"_PUB_TEST_SDK_VERSION": "1.2.3+4"});
       });
 
       _requiresPubGet("Dart 0.1.2+3 is incompatible with your dependencies' "
           "SDK constraints. Please run \"pub get\" again.");
     });
 
+    integration("the lock file's Flutter SDK constraint doesn't match the "
+        "current Flutter SDK", () {
+      // Avoid using a path dependency because it triggers the full validation
+      // logic. We want to be sure SDK-validation works without that logic.
+      globalPackageServer.add((builder) {
+        builder.serve("foo", "3.0.0", pubspec: {
+          "environment": {"flutter": ">=1.0.0 <2.0.0"}
+        });
+      });
+
+      d.dir('flutter', [
+        d.file('version', '1.2.3')
+      ]).create();
+
+      d.dir(appPath, [
+        d.appPubspec({"foo": "3.0.0"})
+      ]).create();
+
+      pubGet(environment: {"FLUTTER_ROOT": p.join(sandboxDir, 'flutter')});
+
+      d.dir('flutter', [
+        d.file('version', '2.4.6')
+      ]).create();
+
+      // Run pub manually here because otherwise we don't have access to
+      // sandboxDir.
+      schedulePub(
+          args: ["run", "script"],
+          environment: {"FLUTTER_ROOT": p.join(sandboxDir, 'flutter')},
+          error: "Flutter 2.4.6 is incompatible with your dependencies' SDK "
+                   "constraints. Please run \"pub get\" again.",
+          exitCode: exit_codes.DATA);
+    });
+
     group("a path dependency's dependency doesn't match the lockfile", () {
       setUp(() {
         d.dir("bar", [
           d.libPubspec("bar", "1.0.0", deps: {"foo": "1.0.0"})
         ]).create();
 
         d.dir(appPath, [
           d.appPubspec({"bar": {"path": "../bar"}})
         ]).create();
 
@@ skipping 88 matching lines @@
           })
         ]).create();
 
         pubGet();
 
         _touch("pubspec.lock");
       });
 
       _runsSuccessfully();
     });
+
+    integration("the lock file has a Flutter SDK but Flutter is unavailable",
+        () {
+      // Avoid using a path dependency because it triggers the full validation
+      // logic. We want to be sure SDK-validation works without that logic.
+      globalPackageServer.add((builder) {
+        builder.serve("foo", "3.0.0", pubspec: {
+          "environment": {"flutter": ">=1.0.0 <2.0.0"}
+        });
+      });
+
+      d.dir('flutter', [
+        d.file('version', '1.2.3')
+      ]).create();
+
+      d.dir(appPath, [
+        d.appPubspec({"foo": "3.0.0"})
+      ]).create();
+
+      pubGet(environment: {"FLUTTER_ROOT": p.join(sandboxDir, 'flutter')});
+
+      d.dir('flutter', [
+        d.file('version', '2.4.6')
+      ]).create();
+
+      // Run pub manually here because otherwise we don't have access to
+      // sandboxDir.
+      schedulePub(args: ["run", "bin/script.dart"]);
+    });
   });
 }
 
 /// Runs every command that care about the world being up-to-date, and asserts
 /// that it prints [message] as part of its error.
+///
+/// If [environment] is passed, it's called to produce a map that's merged into
+/// the OS environment for the pub commands.
 void _requiresPubGet(String message) {
   for (var command in ["build", "serve", "run", "deps"]) {
     integration("for pub $command", () {
       var args = [command];
       if (command == "run") args.add("script");
 
       schedulePub(
           args: args,
           error: contains(message),
           exitCode: exit_codes.DATA);
@@ skipping 46 matching lines @@
 void _touch(String path) {
   schedule(() async {
     // Delay a bit to make sure the modification times are noticeably different.
     // 1s seems to be the finest granularity that dart:io reports.
     await new Future.delayed(new Duration(seconds: 1));
 
     path = p.join(sandboxDir, "myapp", path);
     touch(path);
   }, "touching $path");
 }