Add a platform plugin infrastructure.

lib/src/runner/loader.dart

Index: lib/src/runner/loader.dart
diff --git a/lib/src/runner/loader.dart b/lib/src/runner/loader.dart
index b7594db40536b4bc904c9b47078422a91d145e44..6e68ee20aa1ce8c96dec24a9df0be1f2d75fc512 100644
--- a/lib/src/runner/loader.dart
+++ b/lib/src/runner/loader.dart
@@ -4,30 +4,25 @@
 
 import 'dart:async';
 import 'dart:io';
-import 'dart:isolate';
 
 import 'package:analyzer/analyzer.dart' hide Configuration;
 import 'package:async/async.dart';
 import 'package:path/path.dart' as p;
-import 'package:stack_trace/stack_trace.dart';
 
 import '../backend/group.dart';
 import '../backend/metadata.dart';
-import '../backend/test.dart';
 import '../backend/test_platform.dart';
-import '../util/dart.dart' as dart;
 import '../util/io.dart';
-import '../util/remote_exception.dart';
 import '../utils.dart';
 import 'browser/server.dart';
 import 'configuration.dart';
-import 'hack_load_vm_file_hook.dart';
 import 'load_exception.dart';
 import 'load_suite.dart';
 import 'parse_metadata.dart';
+import 'plugin/environment.dart';
+import 'plugin/platform.dart';
 import 'runner_suite.dart';
-import 'vm/environment.dart';
-import 'vm/isolate_test.dart';
+import 'vm/platform.dart';
 
 /// A class for finding test files and loading them into a runnable form.
 class Loader {
@@ -40,6 +35,11 @@ class Loader {
   /// All suites that have been created by the loader.
   final _suites = new Set<RunnerSuite>();
 
+  /// Plugins for loading test suites for various platforms.
+  ///
+  /// This includes the built-in [VMPlatform] plugin.
+  final _platformPlugins = <TestPlatform, PlatformPlugin>{};
+
   /// The server that serves browser test pages.
   ///
   /// This is lazily initialized the first time it's accessed.
@@ -58,7 +58,19 @@ class Loader {
   /// [root] is the root directory that will be served for browser tests. It
   /// defaults to the working directory.
   Loader(this._config, {String root})
-      : _root = root == null ? p.current : root;
+      : _root = root == null ? p.current : root {
+    registerPlatformPlugin(new VMPlatform(_config));
+  }
+
+  /// Registers [plugin] as a plugin for the platforms it defines in
+  /// [PlatformPlugin.platforms].
+  ///
+  /// This overwrites previous plugins for those platforms.
+  void registerPlatformPlugin(PlatformPlugin plugin) {
+    for (var platform in plugin.platforms) {
+      _platformPlugins[platform] = plugin;
+    }
+  }
 
   /// Loads all test suites in [dir].
   ///
@@ -119,17 +131,27 @@ class Loader {
       // Don't load a skipped suite.
       if (metadata.skip) {
         yield new LoadSuite.forSuite(new RunnerSuite(
-            const VMEnvironment(),
+            const PluginEnvironment(),
             new Group.root([], metadata: metadata),
             path: path, platform: platform));
         continue;
       }
 
       var name = (platform.isJS ? "compiling " : "loading ") + path;
-      yield new LoadSuite(name, () {
-        return platform == TestPlatform.vm
-            ? _loadVmFile(path, metadata)
-            : _loadBrowserFile(path, platform, metadata);
+      yield new LoadSuite(name, () async {
+        var plugin = _platformPlugins[platform];
+
+        if (plugin != null) {
+          try {
+            return await plugin.load(path, platform, metadata);
+          } catch (error, stackTrace) {
+            if (error is LoadException) rethrow;
+            await new Future.error(new LoadException(path, error), stackTrace);
+          }
+        }
+
+        assert(platform.isBrowser);
+        return _loadBrowserFile(path, platform, metadata);
       }, path: path, platform: platform);
     }
   }
@@ -141,125 +163,6 @@ class Loader {
         Metadata metadata) async =>
       (await _browserServer).loadSuite(path, platform, metadata);
 
-  /// Load the test suite at [path] in VM isolate.
-  ///
-  /// [metadata] is the suite-level metadata for the test.
-  Future<RunnerSuite> _loadVmFile(String path, Metadata metadata) async {
-    if (loadVMFileHook != null) {
-      var suite = await loadVMFileHook(path, metadata, _config);
-      _suites.add(suite);
-      return suite;
-    }
-
-    var receivePort = new ReceivePort();
-
-    var isolate;
-    try {
-      if (_config.pubServeUrl != null) {
-        var url = _config.pubServeUrl.resolveUri(
-            p.toUri(p.relative(path, from: 'test') + '.vm_test.dart'));
-
-        try {
-          isolate = await Isolate.spawnUri(url, [], {
-            'reply': receivePort.sendPort,
-            'metadata': metadata.serialize()
-          }, checked: true);
-        } on IsolateSpawnException catch (error) {
-          if (error.message.contains("OS Error: Connection refused") ||
-              error.message.contains("The remote computer refused")) {
-            throw new LoadException(path,
-                "Error getting $url: Connection refused\n"
-                'Make sure "pub serve" is running.');
-          } else if (error.message.contains("404 Not Found")) {
-            throw new LoadException(path,
-                "Error getting $url: 404 Not Found\n"
-                'Make sure "pub serve" is serving the test/ directory.');
-          }
-
-          throw new LoadException(path, error);
-        }
-      } else {
-        isolate = await dart.runInIsolate('''
-import "package:test/src/backend/metadata.dart";
-import "package:test/src/runner/vm/isolate_listener.dart";
-
-import "${p.toUri(p.absolute(path))}" as test;
-
-void main(_, Map message) {
-  var sendPort = message['reply'];
-  var metadata = new Metadata.deserialize(message['metadata']);
-  IsolateListener.start(sendPort, metadata, () => test.main);
-}
-''', {
-          'reply': receivePort.sendPort,
-          'metadata': metadata.serialize()
-        }, packageRoot: p.toUri(_config.packageRoot), checked: true);
-      }
-    } catch (error, stackTrace) {
-      receivePort.close();
-      if (error is LoadException) rethrow;
-      await new Future.error(new LoadException(path, error), stackTrace);
-    }
-
-    var completer = new Completer();
-
-    var subscription = receivePort.listen((response) {
-      if (response["type"] == "print") {
-        print(response["line"]);
-      } else if (response["type"] == "loadException") {
-        isolate.kill();
-        completer.completeError(
-            new LoadException(path, response["message"]),
-            new Trace.current());
-      } else if (response["type"] == "error") {
-        isolate.kill();
-        var asyncError = RemoteException.deserialize(response["error"]);
-        completer.completeError(
-            new LoadException(path, asyncError.error),
-            asyncError.stackTrace);
-      } else {
-        assert(response["type"] == "success");
-        completer.complete(response["root"]);
-      }
-    });
-
-    try {
-      var suite = new RunnerSuite(
-          const VMEnvironment(),
-          _deserializeGroup(await completer.future),
-          path: path,
-          platform: TestPlatform.vm,
-          os: currentOS,
-          onClose: isolate.kill);
-      _suites.add(suite);
-      return suite;
-    } finally {
-      subscription.cancel();
-    }
-  }
-
-  /// Deserializes [group] into a concrete [Group] class.
-  Group _deserializeGroup(Map group) {
-    var metadata = new Metadata.deserialize(group['metadata']);
-    return new Group(group['name'], group['entries'].map((entry) {
-      if (entry['type'] == 'group') return _deserializeGroup(entry);
-      return _deserializeTest(entry);
-    }),
-        metadata: metadata,
-        setUpAll: _deserializeTest(group['setUpAll']),
-        tearDownAll: _deserializeTest(group['tearDownAll']));
-  }
-
-  /// Deserializes [test] into a concrete [Test] class.
-  ///
-  /// Returns `null` if [test] is `null`.
-  Test _deserializeTest(Map test) {
-    if (test == null) return null;
-
-    var metadata = new Metadata.deserialize(test['metadata']);
-    return new IsolateTest(test['name'], metadata, test['sendPort']);
-  }
-
   /// Close all the browsers that the loader currently has open.
   ///
   /// Note that this doesn't close the loader itself. Browser tests can still be