[gn] Detect location of Visual Studio in the registry.

build/toolchain/win/setup_toolchain.py

 # 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.
 #
 # Copies the given "win tool" (which the toolchain uses to wrap compiler
 # invocations) and the environment blocks for the 32-bit and 64-bit builds on
 # Windows to the build directory.
 #
 # The arguments are the visual studio install location and the location of the
 # win tool. The script assumes that the root build directory is the current dir
 # and the files will be written to the current directory.
 
 import errno
 import os
 import re
 import subprocess
 import sys
 
+SCRIPT_DIR = os.path.dirname(__file__)
 
 def _ExtractImportantEnvironment(output_of_set):
   """Extracts environment variables required for the toolchain to run from
   a textual dump output by the cmd.exe 'set' command."""
   envvars_to_save = (
       'goma_.*', # TODO(scottmg): This is ugly, but needed for goma.
       'include',
       'lib',
       'libpath',
       'path',
@@ skipping 19 matching lines @@
           setting = os.path.dirname(sys.executable) + os.pathsep + setting
         env[var.upper()] = setting
         break
   for required in ('SYSTEMROOT', 'TEMP', 'TMP'):
     if required not in env:
       raise Exception('Environment variable "%s" '
                       'required to be set to valid path' % required)
   return env
 
 
+def _DetectVisualStudioPath():
+  """Return path to the GYP_MSVS_VERSION of Visual Studio.
+  """
+
+  # Use the code in build/vs_toolchain.py to avoid duplicating code.
+  chromium_dir = os.path.abspath(os.path.join(SCRIPT_DIR, '..', '..', '..'))
+  sys.path.append(os.path.join(chromium_dir, 'build'))
+  import vs_toolchain
+  return vs_toolchain.DetectVisualStudioPath()
+
+
 def _SetupScript(target_cpu, sdk_dir):
   """Returns a command (with arguments) to be used to set up the
   environment."""
   # Check if we are running in the SDK command line environment and use
   # the setup script from the SDK if so. |target_cpu| should be either
   # 'x86' or 'x64'.
   assert target_cpu in ('x86', 'x64')
   if bool(int(os.environ.get('DEPOT_TOOLS_WIN_TOOLCHAIN', 1))) and sdk_dir:
     return [os.path.normpath(os.path.join(sdk_dir, 'Bin/SetEnv.Cmd')),
             '/' + target_cpu]
   else:
+    if 'GYP_MSVS_OVERRIDE_PATH' not in os.environ:
+      os.environ['GYP_MSVS_OVERRIDE_PATH'] = _DetectVisualStudioPath()
     # We only support x64-hosted tools.
-    # TODO(scottmg|dpranke): Non-depot_tools toolchain: need to get Visual
-    # Studio install location from registry.
     return [os.path.normpath(os.path.join(os.environ['GYP_MSVS_OVERRIDE_PATH'],
                                           'VC/vcvarsall.bat')),
             'amd64_x86' if target_cpu == 'x86' else 'amd64']
 
 
 def _FormatAsEnvironmentBlock(envvar_dict):
   """Format as an 'environment block' directly suitable for CreateProcess.
   Briefly this is a list of key=value\0, terminated by an additional \0. See
   CreateProcess documentation for more details."""
   block = ''
@@ skipping 78 matching lines @@
     env_block = _FormatAsEnvironmentBlock(env)
     with open('environment.winrt_' + cpu, 'wb') as f:
         f.write(env_block)
 
   assert vc_bin_dir
   print 'vc_bin_dir = "%s"' % vc_bin_dir
 
 
 if __name__ == '__main__':
   main()