gn: make gn gen preserve import statements passed in --args

tools/gn/setup.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 "tools/gn/setup.h"
 
 #include <stdlib.h>
 #include <algorithm>
 #include <sstream>
 #include <utility>
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/memory/ref_counted.h"
 #include "base/process/launch.h"
 #include "base/single_thread_task_runner.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/strings/utf_string_conversions.h"
 #include "build/build_config.h"
+#include "tools/gn/command_format.h"
 #include "tools/gn/commands.h"
 #include "tools/gn/filesystem_utils.h"
 #include "tools/gn/input_file.h"
 #include "tools/gn/parse_tree.h"
 #include "tools/gn/parser.h"
 #include "tools/gn/source_dir.h"
 #include "tools/gn/source_file.h"
 #include "tools/gn/standard_out.h"
 #include "tools/gn/switches.h"
 #include "tools/gn/tokenizer.h"
@@ skipping 220 matching lines @@
 Setup::Setup()
     : build_settings_(),
       loader_(new LoaderImpl(&build_settings_)),
       builder_(loader_.get()),
       root_build_file_("//BUILD.gn"),
       check_public_headers_(false),
       dotfile_settings_(&build_settings_, std::string()),
       dotfile_scope_(&dotfile_settings_),
       fill_arguments_(true) {
   dotfile_settings_.set_toolchain_label(Label());
+
   build_settings_.set_item_defined_callback(
       base::Bind(&ItemDefinedCallback, scheduler_.task_runner(), &builder_));
 
   loader_->set_complete_callback(base::Bind(&DecrementWorkCount));
   // The scheduler's task runner wasn't created when the Loader was created, so
   // we need to set it now.
   loader_->set_task_runner(scheduler_.task_runner());
 }
 
 Setup::~Setup() {
@@ skipping 159 matching lines @@
     return false;
   }
 
   args_root_ = Parser::Parse(args_tokens_, &err);
   if (err.has_error()) {
     err.PrintToStdout();
     return false;
   }
 
   Scope arg_scope(&dotfile_settings_);
+  // set soure dir so relative imports in args work

[brettw, 2016/08/17 22:10:01]

Style guide: Comments should be sentences with caps & periods.

+  SourceDir root_source_dir =
+      SourceDirForCurrentDirectory(build_settings_.root_path());
+  arg_scope.set_source_dir(root_source_dir);
   args_root_->Execute(&arg_scope, &err);
   if (err.has_error()) {
     err.PrintToStdout();
     return false;
   }
 
   // Save the result of the command args.
   Scope::KeyValueMap overrides;
   arg_scope.GetCurrentScopeValues(&overrides);
   build_settings_.build_args().AddArgOverrides(overrides);
   return true;
 }
 
 bool Setup::SaveArgsToFile() {
   ScopedTrace setup_trace(TraceItem::TRACE_SETUP, "Save args file");
 
-  std::ostringstream stream;
-  for (const auto& pair : build_settings_.build_args().GetAllOverrides()) {
-    stream << pair.first.as_string() << " = " << pair.second.ToString(true);
-    stream << std::endl;
-  }
-
   // For the first run, the build output dir might not be created yet, so do
   // that so we can write a file into it. Ignore errors, we'll catch the error
   // when we try to write a file to it below.
   base::FilePath build_arg_file =
       build_settings_.GetFullPath(GetBuildArgFile());
   base::CreateDirectory(build_arg_file.DirName());
 
-  std::string contents = stream.str();
+  std::string contents = args_input_file_->contents();
+  commands::FormatStringToString(contents, false, &contents);
 #if defined(OS_WIN)
   // Use Windows lineendings for this file since it will often open in
   // Notepad which can't handle Unix ones.
   base::ReplaceSubstringsAfterOffset(&contents, 0, "\n", "\r\n");
 #endif
   if (base::WriteFile(build_arg_file, contents.c_str(),
       static_cast<int>(contents.size())) == -1) {
     Err(Location(), "Args file could not be written.",
       "The file is \"" + FilePathToUTF8(build_arg_file) +
         "\"").PrintToStdout();
@@ skipping 254 matching lines @@
       if (err.has_error()) {
         err.PrintToStdout();
         return false;
       }
     }
     build_settings_.set_exec_script_whitelist(std::move(whitelist));
   }
 
   return true;
 }