Include PowerShell in Windows PATH, if available.

slave/run_slave.py

Index: slave/run_slave.py
diff --git a/slave/run_slave.py b/slave/run_slave.py
index 72c5021ec502f20334d466093b1d046b363e5c9a..779f7c959953b3d53a6670ac36a8edc5bee181b2 100755
--- a/slave/run_slave.py
+++ b/slave/run_slave.py
@@ -57,7 +57,7 @@ def IssueReboot():
                               'for %s' % sys.platform)
 
 
-def SigTerm(*args):
+def SigTerm(*_args):
   """Receive a SIGTERM and do nothing."""
   Log('SigTerm: Received SIGTERM, doing nothing.')
 
@@ -433,8 +433,18 @@ def main():
   os.environ['CHROME_HEADLESS'] = '1'
   os.environ['PAGER'] = 'cat'
 
-  # Platform-specific initialization.
+  # Split the path into its components.
+  path_components = os.environ['PATH'].split(os.pathsep)
+  # This function identifies a PATH component that has the supplied phrase in
+  # one of its directories.
+  def get_path_component_containing(phrase):

[agable, 2016/06/24 18:29:16]

This function is only used once, and is defined nearly a hundred lines from
where it is used (albeit, most of those lines are constants). Why make it a
function at all? The name of the function also doesn't denote that it returns
the *first* path component containing the phrase. Honestly I'd just inline it
and comment the loop.

[dnj (Google), 2016/06/24 18:39:59]

My thought was that it is OS-independent and seemed generically useful, so I
wouldn't mind porting more path-derivations over to this method in the future.
However, agreed, I'll go ahead and move it locally.

Actually I'll just switch over to straightforward 'which / dirname'. Why not?

+    phrase = phrase.lower()
+    for c in path_components:
+      if any(phrase == d.lower() for d in c.split(os.sep)):
+        return [c]
+    return []
 
+  # Platform-specific initialization.
   if sys.platform.startswith('win'):
     # list of all variables that we want to keep
     env_var = [
@@ -484,7 +494,8 @@ def main():
 
     remove_all_vars_except(os.environ, env_var)
 
-    # Extend the env variables with the chrome-specific settings.
+    # Extend the env variables with the chrome-specific settings. Tailor the
+    # slave process' (and derivative tasks') PATH environment variable.
     slave_path = [
         depot_tools,
         # Reuse the python executable used to start this script.
@@ -497,6 +508,13 @@ def main():
         # TODO(hinoka): Remove this when its no longer needed crbug.com/481695
         os.path.join(os.environ['SYSTEMDRIVE'], os.sep, 'cmake', 'bin'),
     ]
+
+    # Include Windows PowerShell in PATH, if defined. It does this by looking
+    # through the system path for an element containing a directory named
+    # "WindowsPowerShell", which is assumed to be the component adding
+    # PowerShell to the PATH.
+    slave_path += get_path_component_containing('WindowsPowerShell')
+
     # build_internal/tools contains tools we can't redistribute.
     tools = os.path.join(ROOT_DIR, 'build_internal', 'tools')
     if os.path.isdir(tools):