Better command line error messages

runtime/bin/main.cc

 // Copyright (c) 2012, 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.
 
 #include <stdlib.h>
 #include <string.h>
 #include <stdio.h>
 
 #include "include/dart_api.h"
 #include "include/dart_tools_api.h"
@@ skipping 189 matching lines @@
     return false;
   }
   verbose_option = true;
   return true;
 }
 
 
 static bool ProcessPackageRootOption(const char* arg,
                                      CommandLineOptions* vm_options) {
   ASSERT(arg != NULL);
-  if (*arg == '\0' || *arg == '-') {
+  if (*arg == '-') {
     return false;
   }
   commandline_package_root = arg;
   return true;
 }
 
 
 static bool ProcessPackagesOption(const char* arg,
-                                     CommandLineOptions* vm_options) {
+                                  CommandLineOptions* vm_options) {
   ASSERT(arg != NULL);
-  if ((*arg == '\0') || (*arg == '-')) {
+  if (*arg == '-') {
     return false;
   }
   commandline_packages_file = arg;
   return true;
 }
 
 
 static void* GetHashmapKeyFromString(char* key) {
   return reinterpret_cast<void*>(key);
 }
@@ skipping 353 matching lines @@
     i++;
   }
 
   // Verify consistency of arguments.
   if ((commandline_package_root != NULL) &&
       (commandline_packages_file != NULL)) {
     Log::PrintErr("Specifying both a packages directory and a packages "
                   "file is invalid.\n");
     return -1;
   }
+  if ((commandline_package_root != NULL) &&
+      (strlen(commandline_package_root) == 0)) {
+    Log::PrintErr("Empty package root specified.\n");
+    return -1;
+  }
+  if ((commandline_packages_file != NULL) &&
+      (strlen(commandline_packages_file) == 0)) {
+    Log::PrintErr("Empty package file name specified.\n");
+    return -1;
+  }
   if (is_noopt && gen_snapshot_kind != kNone) {
     Log::PrintErr("Generating a snapshot with dart_noopt is invalid.\n");
     return -1;
   }
   if ((gen_snapshot_kind != kNone) && (snapshot_filename == NULL)) {
     Log::PrintErr("Generating a snapshot requires a filename (--snapshot).\n");
     return -1;
   }
   if ((gen_snapshot_kind != kNone) && run_app_snapshot) {
     Log::PrintErr("Specifying an option to generate a snapshot and"
@@ skipping 1134 matching lines @@
   Platform::Exit(Process::GlobalExitCode());
 }
 
 }  // namespace bin
 }  // namespace dart
 
 int main(int argc, char** argv) {
   dart::bin::main(argc, argv);
   UNREACHABLE();
 }