Implement modular compilation

lib/src/compiler/command.dart

Index: lib/src/compiler/command.dart
diff --git a/lib/src/compiler/command.dart b/lib/src/compiler/command.dart
new file mode 100644
index 0000000000000000000000000000000000000000..2b0eca1c297132f40c324d4c4c14dccb066bb00d
--- /dev/null
+++ b/lib/src/compiler/command.dart
@@ -0,0 +1,74 @@
+// Copyright (c) 2016, 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:convert' show JSON;
+import 'dart:io';
+import 'package:args/command_runner.dart';
+import 'package:analyzer/src/generated/source.dart' show Source;
+import 'package:analyzer/src/summary/package_bundle_reader.dart'
+    show InSummarySource;
+import 'compiler.dart'
+    show BuildUnit, CompilerOptions, JSModuleFile, ModuleCompiler;
+import '../analyzer/context.dart' show AnalyzerOptions;
+import 'package:path/path.dart' as path;
+
+/// The command for invoking the modular compiler.
+class CompileCommand extends Command {
+  get name => 'compile';
+  get description => 'Compile a set of Dart files into a JavaScript module.';
+
+  CompileCommand() {
+    argParser.addOption('out', abbr: 'o', help: 'Output file (required)');
+    CompilerOptions.addArguments(argParser);
+    AnalyzerOptions.addArguments(argParser);
+  }
+
+  @override
+  void run() {
+    var compilerOptions = new CompilerOptions.fromArguments(argResults);
+    var compiler =
+        new ModuleCompiler(new AnalyzerOptions.fromArguments(argResults));
+
+    var outPath = argResults['out'];
+    if (outPath == null) {
+      usageException('Please include the output file location. For example:\n'
+          '    -o PATH/TO/OUTPUT_FILE.js');
+    }
+    var unit = new BuildUnit(path.basenameWithoutExtension(outPath),
+        argResults.rest, _moduleForLibrary);
+
+    JSModuleFile module = compiler.compile(unit, compilerOptions);
+    module.errors.forEach(print);
+
+    if (!module.isValid) throw new CompileErrorException();
+
+    // Write JS file, as well as source map and summary (if requested).
+    new File(outPath).writeAsStringSync(module.code);
+    if (module.sourceMap != null) {
+      var mapPath = outPath + '.map';
+      new File(mapPath)
+          .writeAsStringSync(JSON.encode(module.placeSourceMap(mapPath)));
+    }
+    if (module.summaryBytes != null) {
+      var summaryPath = path.withoutExtension(outPath) + '.sum';
+      new File(summaryPath).writeAsBytesSync(module.summaryBytes);
+    }
+  }
+
+  String _moduleForLibrary(Source source) {
+    if (source is InSummarySource) {
+      return path.basenameWithoutExtension(source.summaryPath);
+    }
+
+    throw usageException(
+        'Imported file "${source.uri}" was not found as a summary or source '
+        'file. Please pass in either the summary or the source file '
+        'for this import.');
+  }
+}
+
+/// Thrown when the input source code has errors.
+class CompileErrorException implements Exception {
+  toString() => '\nPlease fix all errors before compiling (warnings are okay).';
+}