Implement --help option and generalize option parsing.

Review URL: https://chromiumcodereview.appspot.com//10383086

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@7461 260f80e4-7a28-3924-810f-c04153c831b5

lib/compiler/implementation/dart2js.dart

@@ -16,6 +16,38 @@
 
 final String LIBRARY_ROOT = '../../../..';
 
+typedef void HandleOption(String option);
+
+class OptionHandler {
+  String pattern;
+  HandleOption handle;
+
+  OptionHandler(this.pattern, this.handle);
+}
+
+String extractParameter(String argument) {
+  return argument.substring(argument.indexOf('=') + 1);
+}
+
+void parseCommandLine(List<OptionHandler> handlers, List<String> argv) {
+  var patterns = <String>[];
+  for (OptionHandler handler in handlers) {
+    patterns.add(handler.pattern);
+  }
+  var pattern = new RegExp('^(${Strings.join(patterns, ")|(")})\$');
+  assert(pattern.groupCount() == handlers.length);
+  OUTER: for (String argument in argv) {
+    Match match = pattern.firstMatch(argument);
+    for (int i = 0; i < handlers.length; i++) {
+      if (match[i + 1] !== null) {
+        handlers[i].handle(argument);
+        continue OUTER;
+      }
+    }
+    throw 'Internal error: "$argument" did not match';
+  }
+}
+
 void compile(List<String> argv) {
   Uri cwd = getCurrentDirectory();
   bool throwOnError = false;
@@ -25,41 +57,43 @@ void compile(List<String> argv) {
   Uri out = cwd.resolve('out.js');
   List<String> options = new List<String>();
 
+  passThrough(String argument) => options.add(argument);
+
   List<String> arguments = <String>[];
-  for (String argument in argv) {
-    if ('--throw-on-error' == argument) {
-      throwOnError = true;
-    } else if ('--suppress-warnings' == argument) {
-      showWarnings = false;
-    } else if ('--verbose' == argument) {
-      verbose = true;
-    } else if (argument.startsWith('--library-root=')) {
-      String path =
-          nativeToUriPath(argument.substring(argument.indexOf('=') + 1));
+  List<OptionHandler> handlers = <OptionHandler>[
+    new OptionHandler('--throw-on-error', (_) => throwOnError = true),
+    new OptionHandler('--suppress-warnings', (_) => showWarnings = false),
+    new OptionHandler('--verbose', (_) => verbose = true),
+    new OptionHandler('--library-root=.*', (String argument) {
+      String path = nativeToUriPath(extractParameter(argument));
       if (!path.endsWith("/")) path = "$path/";
       libraryRoot = cwd.resolve(path);
-    } else if (argument.startsWith('--out=')) {
-      String path =
-          nativeToUriPath(argument.substring(argument.indexOf('=') + 1));
-      out = cwd.resolve(path);
-    } else if ('--allow-mock-compilation' == argument) {
-      options.add(argument);
-    } else if ('--no-colors' == argument) {
-      colors.enabled = false;
-    } else if ('--enable-checked-mode' == argument) {
-      options.add(argument);
-    } else if (argument.startsWith('-')) {
-      fail('Unknown option $argument.');
-    } else {
+    }),
+    new OptionHandler('--out=.*', (String argument) {
+      out = cwd.resolve(nativeToUriPath(extractParameter(argument)));
+    }),
+    new OptionHandler('--allow-mock-compilation', passThrough),
+    new OptionHandler('--no-colors', (_) => colors.enabled = false),
+    new OptionHandler('--enable-checked-mode|--checked|-c',
+                      (_) => passThrough('--enable_checked_mode')),
+    new OptionHandler('--help', (_) => helpAndExit()),
+    // The following two options must come last.
+    new OptionHandler('-.*', (String argument) {
+      fail('Error: unknown option "$argument".');
+    }),
+    new OptionHandler('.*', (String argument) {
       arguments.add(nativeToUriPath(argument));
-    }
-  }
+    })
+  ];
+
+  parseCommandLine(handlers, argv);
+
   if (arguments.isEmpty()) {
-    fail('No file to compile.');
+    helpAndFail('Error: no file to compile.');
   }
   if (arguments.length > 1) {
     var extra = arguments.getRange(1, arguments.length - 1);
-    fail('Extra arguments: $extra.');
+    helpAndFail('Error: extra arguments: ${Strings.join(extra, " ")}');
   }
 
   Map<String, SourceFile> sourceFiles = <SourceFile>{};
@@ -104,7 +138,7 @@ void compile(List<String> argv) {
   // directly. In effect, we don't support truly asynchronous API.
   String code = api.compile(uri, libraryRoot, provider, handler, options).value;
   if (code === null) {
-    fail('Compilation failed.');
+    fail('Error: compilation failed.');
   }
   writeString(out, code);
   int jsBytesWritten = code.length;
@@ -120,7 +154,7 @@ class AbortLeg {
 
 void writeString(Uri uri, String text) {
   if (uri.scheme != 'file') {
-    fail('Unhandled scheme ${uri.scheme}.');
+    fail('Error: unhandled scheme ${uri.scheme}.');
   }
   var file = new File(uriPathToNative(uri.path)).openSync(FileMode.WRITE);
   file.writeStringSync(text);
@@ -148,6 +182,38 @@ void compilerMain(Options options) {
   compile(argv);
 }
 
+void help() {
+  // This message should be no longer than 22 lines. The default
+  // terminal size normally 80x24. Two lines are used for the prompts
+  // before and after running the compiler.
+  print('''
+dart2js [OPTIONS...] DART-FILE
+
+A Dart to JavaScript compiler.
+
+By default, the compiled JavaScript code is saved to a file named
+out.js in the current directory.
+
+Common options:
+
+  --help      Display this message.
+
+  --out=FILE  Save the output to FILE (default is out.js).
+
+  --checked   Turn on checked mode in generated JavaScript code.
+''');
+}
+
+void helpAndExit() {
+  help();
+  exit(0);
+}
+
+void helpAndFail(String message) {
+  help();
+  fail(message);
+}
+
 void main() {
   try {
     compilerMain(new Options());