GN: Change gen command syntax, support relative dirs.

tools/gn/command_gyp.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <iostream>
 #include <map>
 #include <utility>
 #include <vector>
 
 #include "base/command_line.h"
@@ skipping 406 matching lines @@
     "  executable(\"my_app\") {\n"
     "    deps = [ \":gyp_target\" ]\n"
     "    gyp_file = \"//foo/myapp.gyp\"\n"
     "    sources = ...\n"
     "  }\n";
 
 int RunGyp(const std::vector<std::string>& args) {
   base::ElapsedTimer timer;
   Setups setups;
 
+  const CommandLine* cmdline = CommandLine::ForCurrentProcess();
+
+  // Compute output directory.
+  std::string build_dir;
+  if (args.size() == 1) {
+    build_dir = args[0];
+  } else {
+    // Backwards-compat code for the old invocation that uses
+    // "gn gyp --output=foo"
+    // TODO(brettw) This should be removed when gyp_chromium has been updated.
+
+    // Switch to set the build output directory.
+    const char kSwitchBuildOutput[] = "output";
+    build_dir = cmdline->GetSwitchValueASCII(kSwitchBuildOutput);
+    if (build_dir.empty())
+      build_dir = "//out/Default/";
+  }
+
   // Deliberately leaked to avoid expensive process teardown. We also turn off
   // unused override checking since we want to merge all declared arguments and
   // check those, rather than check each build individually. Otherwise, you
   // couldn't have an arg that was used in only one build type. This comes up
   // because some args are build-type specific.
   setups.debug = new Setup;
   setups.debug->set_check_for_unused_overrides(false);
-  if (!setups.debug->DoSetup())
+  if (!setups.debug->DoSetup(build_dir))
     return 1;
   const char kIsDebug[] = "is_debug";
 
   SourceDir base_build_dir = setups.debug->build_settings().build_dir();
   setups.debug->build_settings().SetBuildDir(
       AppendDirSuffix(base_build_dir, ".Debug"));
 
   // Make a release build based on the debug one. We use a new directory for
   // the build output so that they don't stomp on each other.
   setups.release = new DependentSetup(setups.debug);
@@ skipping 63 matching lines @@
 
   Err err;
   std::pair<int, int> counts = WriteGypFiles(setups, &err);
   if (err.has_error()) {
     err.PrintToStdout();
     return 1;
   }
 
   base::TimeDelta elapsed_time = timer.Elapsed();
 
-  if (!CommandLine::ForCurrentProcess()->HasSwitch(kSwitchQuiet)) {
+  if (!cmdline->HasSwitch(kSwitchQuiet)) {
     OutputString("Done. ", DECORATION_GREEN);
 
     std::string stats = "Wrote " +
         base::IntToString(counts.first) + " targets to " +
         base::IntToString(counts.second) + " GYP files read from " +
         base::IntToString(
             setups.debug->scheduler().input_file_manager()->GetInputFileCount())
         + " GN files in " +
         base::IntToString(elapsed_time.InMilliseconds()) + "ms\n";
 
     OutputString(stats);
   }
 
   return 0;
 }
 
 }  // namespace commands