Update the toolchain if there's a mismatch between the env and win_toolchain.json

build/vs_toolchain.py

 #!/usr/bin/env python
 # Copyright 2014 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.
 
 import json
 import os
 import pipes
 import shutil
 import subprocess
 import sys
 
 
 script_dir = os.path.dirname(os.path.realpath(__file__))
 chrome_src = os.path.abspath(os.path.join(script_dir, os.pardir))
 SRC_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
 sys.path.insert(0, os.path.join(chrome_src, 'tools', 'gyp', 'pylib'))
 json_data_file = os.path.join(script_dir, 'win_toolchain.json')
 
 
 import gyp
 
 
+# Use MSVS2013 as the default toolchain.
+CURRENT_TOOLCHAIN_VERSION = '2013'

[brucedawson, 2016/01/15 21:10:52]

Should probably be "CURRENT_DEFAULT_TOOLCHAIN_VERSION", to better reflect its
actual usage.

[Sébastien Marchand, 2016/01/15 21:21:39]

Done.

+
+
 def SetEnvironmentAndGetRuntimeDllDirs():
   """Sets up os.environ to use the depot_tools VS toolchain with gyp, and
   returns the location of the VS runtime DLLs so they can be copied into
   the output directory after gyp generation.
   """
   vs_runtime_dll_dirs = None
   depot_tools_win_toolchain = \
       bool(int(os.environ.get('DEPOT_TOOLS_WIN_TOOLCHAIN', '1')))
   # When running on a non-Windows host, only do this if the SDK has explicitly
   # been downloaded before (in which case json_data_file will exist).
   if ((sys.platform in ('win32', 'cygwin') or os.path.exists(json_data_file))
       and depot_tools_win_toolchain):
-    if not os.path.exists(json_data_file):
+    if ShouldUpdateToolchain():
       Update()
     with open(json_data_file, 'r') as tempf:
       toolchain_data = json.load(tempf)
 
     toolchain = toolchain_data['path']
     version = toolchain_data['version']
     win_sdk = toolchain_data.get('win_sdk')
     if not win_sdk:
       win_sdk = toolchain_data['win8sdk']
     wdk = toolchain_data['wdk']
@@ skipping 51 matching lines @@
     raise Exception('The python library _winreg not found.')
 
 
 def DetectVisualStudioPath():
   """Return path to the GYP_MSVS_VERSION of Visual Studio.
   """
 
   # Note that this code is used from
   # build/toolchain/win/setup_toolchain.py as well.
 
-  # Default to Visual Studio 2013 for now.
-  version_as_year = os.environ.get('GYP_MSVS_VERSION', '2013')
+  version_as_year = os.environ.get('GYP_MSVS_VERSION',
+                                   CURRENT_TOOLCHAIN_VERSION)
   year_to_version = {
       '2013': '12.0',
       '2015': '14.0',
   }
   if version_as_year not in year_to_version:
     raise Exception(('Visual Studio version %s (from GYP_MSVS_VERSION)'
                      ' not supported. Supported versions are: %s') % (
                        version_as_year, ', '.join(year_to_version.keys())))
   version = year_to_version[version_as_year]
   keys = [r'HKLM\Software\Microsoft\VisualStudio\%s' % version,
@@ skipping 136 matching lines @@
 def _GetDesiredVsToolchainHashes():
   """Load a list of SHA1s corresponding to the toolchains that we want installed
   to build with."""
   if os.environ.get('GYP_MSVS_VERSION') == '2015':
     return ['17c7ddb3595be5c6b9c98b6f930adad7e4456671'] # Update 1
   else:
     # Default to VS2013.
     return ['9ff97c632ae1fee0c98bcd53e71770eb3a0d8deb']
 
 
+def ShouldUpdateToolchain():
+  """Check if the toolchain should be upgraded."""
+  if not os.path.exists(json_data_file):
+    return True
+  with open(json_data_file, 'r') as tempf:
+    toolchain_data = json.load(tempf)
+  version = toolchain_data['version']
+  env_version = os.environ.get('GYP_MSVS_VERSION', CURRENT_TOOLCHAIN_VERSION)
+  # If there's a mismatch between the version set in the environment and the one
+  # in the json file then the toolchain should be updated.
+  if version != env_version:

[scottmg, 2016/01/15 21:08:13]

return version != env_version

[Sébastien Marchand, 2016/01/15 21:21:39]

Done.

+    return True
+  return False
+
+
 def Update(force=False):
   """Requests an update of the toolchain to the specific hashes we have at
   this revision. The update outputs a .json of the various configuration
   information required to pass to gyp which we use in |GetToolchainDir()|.
   """
   if force != False and force != '--force':
     print >>sys.stderr, 'Unknown parameter "%s"' % force
     return 1
   if force == '--force' or os.path.exists(json_data_file):
     force = True
@@ skipping 49 matching lines @@
       'copy_dlls': CopyDlls,
   }
   if len(sys.argv) < 2 or sys.argv[1] not in commands:
     print >>sys.stderr, 'Expected one of: %s' % ', '.join(commands)
     return 1
   return commands[sys.argv[1]](*sys.argv[2:])
 
 
 if __name__ == '__main__':
   sys.exit(main())