Add initial support for build_runner serve (#4)

Refactor shared arguments into abstract class.

Author: nshahan

webdev/lib/src/command/build_command.dart

@@ -1,29 +1,17 @@
 import 'dart:async';
+
 import 'package:io/io.dart';
 
-import 'package:args/command_runner.dart';
+import 'build_runner_command_base.dart';
 
 /// Command to execute pub run build_runner build.
-class BuildCommand extends Command {
+class BuildCommand extends BuildRunnerCommandBase {
   @override
   final name = 'build';
 
   @override
   final description = 'Run builders to build a package.';
 
-  BuildCommand() {
-    // TODO(nshahan) Expose more args passed to build_runner build.
-    // build_runner might expose args for use in wrapping scripts like this one.
-    argParser
-      ..addOption('output',
-          abbr: 'o', help: 'A directory to write the result of a build to.')
-      ..addFlag('verbose',
-          abbr: 'v',
-          defaultsTo: false,
-          negatable: false,
-          help: 'Enables verbose logging.');
-  }
-
   @override
   Future run() async {
     final manager = new ProcessManager();

webdev/lib/src/command/build_runner_command_base.dart

@@ -0,0 +1,18 @@
+import 'package:args/command_runner.dart';
+
+/// Extend to get a command with the arguments common to all build_runner
+/// commands.
+abstract class BuildRunnerCommandBase extends Command {
+  BuildRunnerCommandBase() {
+    // TODO(nshahan) Expose more common args passed to build_runner commands.
+    // build_runner might expose args for use in wrapping scripts like this one.
+    argParser
+      ..addOption('output',
+          abbr: 'o', help: 'A directory to write the result of a build to.')
+      ..addFlag('verbose',
+          abbr: 'v',
+          defaultsTo: false,
+          negatable: false,
+          help: 'Enables verbose logging.');
+  }
+}

webdev/lib/src/command/serve_command.dart

@@ -0,0 +1,35 @@
+import 'dart:async';
+
+import 'package:io/io.dart';
+
+import 'build_runner_command_base.dart';
+
+/// Command to execute pub run build_runner serve.
+class ServeCommand extends BuildRunnerCommandBase {
+  @override
+  final name = 'serve';
+
+  @override
+  final description = 'Run a local web development server and a file system'
+      ' watcher that re-builds on changes.';
+
+  ServeCommand() {
+    // TODO(nshahan) Expose more args passed to build_runner serve.
+    // build_runner might expose args for use in wrapping scripts like this one.
+    argParser
+      ..addOption('hostname',
+          defaultsTo: 'localhost', help: 'Specify the hostname to serve on.');
+  }
+
+  @override
+  Future run() async {
+    final manager = new ProcessManager();
+    final executable = 'pub';
+    final arguments = ['run', 'build_runner', 'serve', '--assume-tty'];
+    arguments.addAll(argResults.arguments);
+    var spawn = await manager.spawn(executable, arguments);
+
+    await spawn.exitCode;
+    await sharedStdIn.terminate();
+  }
+}

webdev/lib/src/webdev_command_runner.dart

@@ -1,13 +1,10 @@
 import 'package:args/command_runner.dart';
 
 import 'command/build_command.dart';
+import 'command/serve_command.dart';
 
 /// All available top level commands.
-CommandRunner webdevCommandRunner() {
-  final commandRunner =
-      new CommandRunner('webdev', 'A tool to develop Dart web projects.');
-
-  commandRunner.addCommand(new BuildCommand());
-
-  return commandRunner;
-}
+CommandRunner webdevCommandRunner() =>
+    new CommandRunner('webdev', 'A tool to develop Dart web projects.')
+      ..addCommand(new BuildCommand())
+      ..addCommand(new ServeCommand());