Only import gyp when required in vs_toolchain.py.

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 glob
 import json
 import os
 import pipes
 import platform
 import shutil
 import stat
 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 MSVS2015 as the default toolchain.
 CURRENT_DEFAULT_TOOLCHAIN_VERSION = '2015'
 
 
 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.
 
   Return value is [x64path, x86path] or None
@@ skipping 16 matching lines @@
     if not win_sdk:
       win_sdk = toolchain_data['win8sdk']
     wdk = toolchain_data['wdk']
     # TODO(scottmg): The order unfortunately matters in these. They should be
     # split into separate keys for x86 and x64. (See CopyVsRuntimeDlls call
     # below). http://crbug.com/345992
     vs_runtime_dll_dirs = toolchain_data['runtime_dirs']
 
     os.environ['GYP_MSVS_OVERRIDE_PATH'] = toolchain
     os.environ['GYP_MSVS_VERSION'] = version
+
+    # Limit the scope of the gyp import to only where it is used. This
+    # potentially lets build configs that never execute this block to drop
+    # their GYP checkout.
+    import gyp
+
     # We need to make sure windows_sdk_path is set to the automated
     # toolchain values in GYP_DEFINES, but don't want to override any
     # otheroptions.express
     # values there.
     gyp_defines_dict = gyp.NameValueListToDict(gyp.ShlexEnv('GYP_DEFINES'))
     gyp_defines_dict['windows_sdk_path'] = win_sdk
     os.environ['GYP_DEFINES'] = ' '.join('%s=%s' % (k, pipes.quote(str(v)))
         for k, v in gyp_defines_dict.iteritems())
+
     os.environ['WINDOWSSDKDIR'] = win_sdk
     os.environ['WDK_DIR'] = wdk
     # Include the VS runtime in the PATH in case it's not machine-installed.
     runtime_path = os.path.pathsep.join(vs_runtime_dll_dirs)
     os.environ['PATH'] = runtime_path + os.path.pathsep + os.environ['PATH']
   elif sys.platform == 'win32' and not depot_tools_win_toolchain:
     if not 'GYP_MSVS_OVERRIDE_PATH' in os.environ:
       os.environ['GYP_MSVS_OVERRIDE_PATH'] = DetectVisualStudioPath()
     if not 'GYP_MSVS_VERSION' in os.environ:
       os.environ['GYP_MSVS_VERSION'] = GetVisualStudioVersion()
@@ skipping 83 matching lines @@
   raise Exception(('Visual Studio Version %s (from GYP_MSVS_VERSION)'
                    ' not found.') % (version_as_year))
 
 
 def _VersionNumber():
   """Gets the standard version number ('120', '140', etc.) based on
   GYP_MSVS_VERSION."""
   vs_version = GetVisualStudioVersion()
   if vs_version == '2013':
     return '120'
-  elif vs_version == '2015':
+  if vs_version == '2015':
     return '140'
-  elif vs_version == '2017':
+  if vs_version == '2017':
     return '150'
-  else:
-    raise ValueError('Unexpected GYP_MSVS_VERSION')
+  raise ValueError('Unexpected GYP_MSVS_VERSION')
 
 
 def _CopyRuntimeImpl(target, source, verbose=True):
   """Copy |source| to |target| if it doesn't already exist or if it needs to be
   updated (comparing last modified time as an approximate float match as for
   some reason the values tend to differ by ~1e-07 despite being copies of the
   same file... https://crbug.com/603603).
   """
   if (os.path.isdir(os.path.dirname(target)) and
       (not os.path.isfile(target) or
@@ skipping 143 matching lines @@
 
   for debug_file in debugger_files:
     full_path = os.path.join(win_sdk_dir, 'Debuggers', target_cpu, debug_file)
     target_path = os.path.join(target_dir, debug_file)
     _CopyRuntimeImpl(target_path, full_path)
 
 
 def _GetDesiredVsToolchainHashes():
   """Load a list of SHA1s corresponding to the toolchains that we want installed
   to build with."""
-  if GetVisualStudioVersion() == '2015':
+  env_version = GetVisualStudioVersion()
+  if env_version == '2013':
+    return ['03a4e939cd325d6bc5216af41b92d02dda1366a6']
+  if env_version == '2015':
     # Update 3 final with patches with 10.0.14393.0 SDK.
     return ['d3cb0e37bdd120ad0ac4650b674b09e81be45616']
-  elif GetVisualStudioVersion() == '2013':
-    return ['03a4e939cd325d6bc5216af41b92d02dda1366a6']
-  else:
-    raise Exception('Unsupported VS version %s' % GetVisualStudioVersion())
+  raise Exception('Unsupported VS version %s' % env_version)
 
 
 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 = GetVisualStudioVersion()
@@ skipping 82 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())