add verbose option to show hidden args

pkg/dev_compiler/lib/src/compiler/command.dart

 // 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:io';
 import 'package:analyzer/src/generated/source.dart' show Source;
 import 'package:analyzer/src/summary/package_bundle_reader.dart'
     show InSummarySource;
 import 'package:args/args.dart' show ArgParser, ArgResults;
 import 'package:args/command_runner.dart' show UsageException;
 import 'package:path/path.dart' as path;
 
 import '../analyzer/context.dart' show AnalyzerOptions, parseDeclaredVariables;
 import 'compiler.dart' show BuildUnit, CompilerOptions, ModuleCompiler;
 import 'module_builder.dart';
 
-final ArgParser _argParser = () {
-  var argParser = new ArgParser(allowTrailingOptions: true)
-    ..addFlag('help', abbr: 'h', help: 'Display this message.')
-    ..addOption('out',
-        abbr: 'o', allowMultiple: true, help: 'Output file (required).')
-    ..addOption('module-root',
-        help: 'Root module directory.\n'
-            'Generated module paths are relative to this root.')
-    ..addOption('library-root',
-        help: 'Root of source files.\n'
-            'Generated library names are relative to this root.');
-  addModuleFormatOptions(argParser, allowMultiple: true);
-  AnalyzerOptions.addArguments(argParser);
-  CompilerOptions.addArguments(argParser);
-  return argParser;
-}();
+bool _verbose = false;
 
 /// Runs a single compile for dartdevc.
 ///
 /// This handles argument parsing, usage, error handling.
 /// See bin/dartdevc.dart for the actual entry point, which includes Bazel
 /// worker support.
 int compile(List<String> args, {void printFn(Object obj)}) {
   printFn ??= print;
   ArgResults argResults;
   var declaredVars = <String, String>{};
   try {
-    argResults = _argParser.parse(parseDeclaredVariables(args, declaredVars));
+    argResults = _argParser().parse(parseDeclaredVariables(args, declaredVars));
+    _verbose = argResults['verbose'];
   } on FormatException catch (error) {
     printFn('$error\n\n$_usageMessage');
     return 64;
   }
   try {
     _compile(argResults, declaredVars, printFn);
     return 0;
   } on UsageException catch (error) {
     // Incorrect usage, input file not found, etc.
     printFn(error);
@@ skipping 18 matching lines @@
     dartdevc arguments: ${args.join(' ')}
     dart --version: ${Platform.version}
 ```
 $error
 $stackTrace
 ```''');
     return 70;
   }
 }
 
+ArgParser _argParser({bool hide: true}) {
+  var argParser = new ArgParser(allowTrailingOptions: true)
+    ..addFlag('help',
+        abbr: 'h',
+        help: 'Display this message.\n'
+            'Add --verbose to show hidden options.',
+        negatable: false)
+    ..addFlag('verbose', abbr: 'v', help: 'Verbose output.')
+    ..addOption('out',
+        abbr: 'o', allowMultiple: true, help: 'Output file (required).')
+    ..addOption('module-root',
+        help: 'Root module directory.\n'
+            'Generated module paths are relative to this root.')
+    ..addOption('library-root',
+        help: 'Root of source files.\n'
+            'Generated library names are relative to this root.');
+  addModuleFormatOptions(argParser, allowMultiple: true, hide: hide);
+  AnalyzerOptions.addArguments(argParser, hide: hide);
+  CompilerOptions.addArguments(argParser, hide: hide);
+  return argParser;
+}
+
 bool _changed(List<int> list1, List<int> list2) {
   var length = list1.length;
   if (length != list2.length) return true;
   for (var i = 0; i < length; ++i) {
     if (list1[i] != list2[i]) return true;
   }
   return false;
 }
 
 void _compile(ArgResults argResults, Map<String, String> declaredVars,
@@ skipping 98 matching lines @@
         'directory $moduleRoot');
   }
 
   _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.');
   return null; // unreachable
 }
 
-final _usageMessage =
+String get _usageMessage =>
     'Dart Development Compiler compiles Dart into a JavaScript module.'
-    '\n\n${_argParser.usage}';
+        '\n\n${_argParser(hide: !_verbose).usage}';
 
 void _usageException(String message) {
   throw new UsageException(message, _usageMessage);
 }
 
 /// Thrown when the input source code has errors.
 class CompileErrorException implements Exception {
   toString() => '\nPlease fix all errors before compiling (warnings are okay).';
 }