GN: Use build directory for CD for scripts

tools/gn/function_exec_script.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 "base/command_line.h"
 #include "base/file_util.h"
 #include "base/logging.h"
 #include "base/process/kill.h"
 #include "base/process/launch.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 224 matching lines @@
 const char kExecScript_Help[] =
     "exec_script: Synchronously run a script and return the output.\n"
     "\n"
     "  exec_script(filename, arguments, input_conversion,\n"
     "              [file_dependencies])\n"
     "\n"
     "  Runs the given script, returning the stdout of the script. The build\n"
     "  generation will fail if the script does not exist or returns a nonzero\n"
     "  exit code.\n"
     "\n"
+    "  The current directory when executing the script will be the root\n"
+    "  build directory. If you are passing file names, you will want to use\n"
+    "  the to_build_dir() function to make file names relative to this\n"
+    "  path (see \"gn help to_build_dir\").\n"
+    "\n"
     "Arguments:\n"
     "\n"
     "  filename:\n"
-    "      File name of python script to execute, relative to the build file.\n"
+    "      File name of python script to execute. Non-absolute names will\n"
+    "      be treated as relative to the current build file.\n"
     "\n"
     "  arguments:\n"
     "      A list of strings to be passed to the script as arguments.\n"
     "\n"
     "  input_conversion:\n"
     "      Controls how the file is read and parsed.\n"
     "      See \"gn help input_conversion\".\n"
     "\n"
     "  dependencies:\n"
     "      (Optional) A list of files that this script reads or otherwise\n"
     "      depends on. These dependencies will be added to the build result\n"
     "      such that if any of them change, the build will be regenerated and\n"
     "      the script will be re-run.\n"
     "\n"
     "      The script itself will be an implicit dependency so you do not\n"
     "      need to list it.\n"
     "\n"
     "Example:\n"
     "\n"
     "  all_lines = exec_script(\"myscript.py\", [some_input], \"list lines\",\n"
-    "                          [\"data_file.txt\"])\n";
+    "                          [ to_build_dir(\"data_file.txt\") ])\n";
 
 Value RunExecScript(Scope* scope,
                     const FunctionCallNode* function,
                     const std::vector<Value>& args,
                     Err* err) {
   if (args.size() != 3 && args.size() != 4) {
     *err = Err(function->function(), "Wrong number of args to write_file",
                "I expected three or four arguments.");
     return Value();
   }
@@ skipping 49 matching lines @@
   base::TimeTicks begin_exec;
   if (g_scheduler->verbose_logging()) {
 #if defined(OS_WIN)
     g_scheduler->Log("Pythoning", UTF16ToUTF8(cmdline.GetCommandLineString()));
 #else
     g_scheduler->Log("Pythoning", cmdline.GetCommandLineString());
 #endif
     begin_exec = base::TimeTicks::Now();
   }
 
+  base::FilePath startup_dir =
+      build_settings->GetFullPath(build_settings->build_dir());
+
   // Execute the process.
   // TODO(brettw) set the environment block.
   std::string output;
   std::string stderr_output;  // TODO(brettw) not hooked up, see above.
   int exit_code = 0;
-  if (!ExecProcess(cmdline, build_settings->GetFullPath(cur_dir),
+  if (!ExecProcess(cmdline, startup_dir,
                    &output, &stderr_output, &exit_code)) {
     *err = Err(function->function(), "Could not execute python.",
         "I was trying to execute \"" + FilePathToUTF8(python_path) + "\".");
     return Value();
   }
   if (g_scheduler->verbose_logging()) {
     g_scheduler->Log("Pythoning", script_source.value() + " took " +
         base::Int64ToString(
             (base::TimeTicks::Now() - begin_exec).InMilliseconds()) +
         "ms");
   }
 
   // TODO(brettw) maybe we need stderr also for reasonable stack dumps.
   if (exit_code != 0) {
-    std::string msg = "Current dir: " +
-        FilePathToUTF8(build_settings->GetFullPath(cur_dir)) + "\nCommand: " +
-        cmdline.GetCommandLineString() +
+    std::string msg = "Current dir: " + FilePathToUTF8(startup_dir) +
+        "\nCommand: " + cmdline.GetCommandLineString() +
         "\nReturned " + base::IntToString(exit_code);
     if (!output.empty())
       msg += " and printed out:\n\n" + output;
     else
       msg += ".";
     *err = Err(function->function(), "Script returned non-zero exit code.",
                msg);
     return Value();
   }
 
   return ConvertInputToValue(output, function, args[2], err);
 }
 
 }  // namespace functions