Include PowerShell in Windows PATH, if available.

scripts/common/chromium_utils.py

 # Copyright (c) 2012 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.
 
 """ Set of basic operations/utilities that are used by the build. """
 
 from contextlib import contextmanager
 import ast
 import base64
 import cStringIO
@@ skipping 2021 matching lines @@
     return False
   # Matches e.g. "cl_x86 = path/to/clang-cl.exe"
   clang_cl_re = re.compile(
       r'^cl_x\d\d\s+\=\s+(?P<compiler_path>[^ ]+)\s.*$',
       re.VERBOSE)
   for line in open(build_file):
     m = clang_cl_re.match(line)
     if m:
       return 'clang' in m.group('compiler_path')
   return False
+
+# Everything below this point has been copied from the Python-3.3 sources with
+# the following modifications:
+#
+# The variable, "dir", was renamed to "pathcomp", since "dir" is a Python
+# reserved word.
+def Which(cmd, mode=os.F_OK | os.X_OK, path=None):
+  """Given a command, mode, and a PATH string, return the path which
+  conforms to the given mode on the PATH, or None if there is no such
+  file.
+  `mode` defaults to os.F_OK | os.X_OK. `path` defaults to the result
+  of os.environ.get("PATH"), or can be overridden with a custom search
+  path.
+  """
+  # Check that a given file can be accessed with the correct mode.
+  # Additionally check that `file` is not a directory, as on Windows
+  # directories pass the os.access check.
+  def _access_check(fn, mode):
+    return (os.path.exists(fn) and os.access(fn, mode)
+            and not os.path.isdir(fn))
+
+  # Short circuit. If we're given a full path which matches the mode
+  # and it exists, we're done here.
+  if _access_check(cmd, mode):
+    return cmd
+
+  path = (path or os.environ.get("PATH", os.defpath)).split(os.pathsep)
+
+  if sys.platform == "win32":
+    # The current directory takes precedence on Windows.
+    if not os.curdir in path:
+      path.insert(0, os.curdir)
+
+    # PATHEXT is necessary to check on Windows.
+    pathext = os.environ.get("PATHEXT", "").split(os.pathsep)
+    # See if the given file matches any of the expected path extensions.
+    # This will allow us to short circuit when given "python.exe".
+    matches = [cmd for ext in pathext if cmd.lower().endswith(ext.lower())]
+    # If it does match, only test that one, otherwise we have to try
+    # others.
+    files = [cmd] if matches else [cmd + ext.lower() for ext in pathext]
+  else:
+    # On other platforms you don't have things like PATHEXT to tell you
+    # what file suffixes are executable, so just pass on cmd as-is.
+    files = [cmd]
+
+  seen = set()
+  for pathcomp in path:
+    pathcomp = os.path.normcase(pathcomp)
+    if not pathcomp in seen:
+      seen.add(pathcomp)
+      for thefile in files:
+        name = os.path.join(pathcomp, thefile)
+        if _access_check(name, mode):
+          return name
+  return None