Formatter selection preservation support.

pkg/analyzer_experimental/bin/formatter.dart

 #!/usr/bin/env 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:convert';
 import 'dart:io';
 import 'dart:utf';
 
 import 'package:args/args.dart';
 import 'package:path/path.dart' as path;
 
 import 'package:analyzer_experimental/src/services/formatter_impl.dart';
 
 
 const BINARY_NAME = 'dartfmt';
 final dartFileRegExp = new RegExp(r'^[^.].*\.dart$', caseSensitive: false);
 final argParser = _initArgParser();
 
+bool machineFormat;
 bool overwriteFileContents;
+Selection selection;
 const followLinks = false;
 
 main() {
   var options = argParser.parse(new Options().arguments);
   if (options['help']) {
     _printUsage();
     return;
   }
-  overwriteFileContents = options['write'];
 
+  _readOptions(options);
+  
   if (options.rest.isEmpty) {
     _formatStdin(options);
   } else {
     _formatPaths(options.rest);
   }
 }
 
+_readOptions(options) {
+  machineFormat = options['machine'];
+  overwriteFileContents = options['write'];
+  selection = _parseSelection(options['selection']);
+}
+
+Selection _parseSelection(selectionOption) {
+  if (selectionOption != null) {
+    var units = selectionOption.split(',');
+    if (units.length == 2) {
+      var offset = _toInt(units[0]);
+      var length = _toInt(units[1]);
+      if (offset != null && length != null) {
+        return new Selection(offset, length);
+      }
+    }
+    throw new FormatterException('Selections are specified as integer pairs '
+                                 '(e.g., "(offset, length)".');
+  }
+}
+
+int _toInt(str) => int.parse(str, onError: (_) => null);
+
 _formatPaths(paths) {
   paths.forEach((path) {
     if (FileSystemEntity.isDirectorySync(path)) {
       _formatDirectory(new Directory(path));
     } else {
       _formatFile(new File(path));
     }
   });
 }
 
@@ skipping 35 matching lines @@
         onDone: () => print(_formatCU(input.toString())));
 }
 
 /// Initialize the arg parser instance.
 ArgParser _initArgParser() {
   // NOTE: these flags are placeholders only!
   var parser = new ArgParser();
   parser.addFlag('write', abbr: 'w', negatable: false,
       help: 'Write reformatted sources to files (overwriting contents).  '
             'Do not print reformatted sources to standard output.');
+  parser.addFlag('machine', abbr: 'm', negatable: false,
+      help: 'Produce output in a format suitable for parsing.');
+  parser.addOption('selection', abbr: 's',
+      help: 'Specify selection information as an offset,length pair '
+            '(e.g., -s "0,4").');
   parser.addFlag('help', abbr: 'h', negatable: false,
       help: 'Print this usage information.');
   return parser;
 }
 
 
 /// Displays usage information.
 _printUsage() {
   var buffer = new StringBuffer();
   buffer..write('$BINARY_NAME formats Dart programs.')
         ..write('\n\n')
         ..write('Without an explicit path, $BINARY_NAME processes the standard '
                 'input.  Given a file, it operates on that file; given a '
                 'directory, it operates on all .dart files in that directory, '
                 'recursively. (Files starting with a period are ignored.) By '
                 'default, $BINARY_NAME prints the reformatted sources to '
                 'standard output.')
         ..write('\n\n')
         ..write('Supported flags are:')
         ..write('Usage: $BINARY_NAME [flags] [path...]\n\n')
         ..write('${argParser.getUsage()}\n\n');
   _log(buffer.toString());
 }
 
 /// Format the given [src] as a compilation unit.
-String _formatCU(src, {options: const FormatterOptions()}) =>
-    new CodeFormatter(options).format(CodeKind.COMPILATION_UNIT, src).source;
+String _formatCU(src, {options: const FormatterOptions()}) {
+  var formatResult = new CodeFormatter(options).format(
+      CodeKind.COMPILATION_UNIT, src, selection: selection);
+  if (machineFormat) {
+    return _toJson(formatResult);
+  }
+  return formatResult.source;
+}
+
+_toJson(formatResult) => 
+    // Actual JSON format TBD
+    JSON.encode({'source': formatResult.source,
+                 'selection': formatResult.selection.toString()});
 
 /// Log the given [msg].
 _log(String msg) {
   //TODO(pquitslund): add proper log support
   print(msg);
 }