Try to better guess Visual Studio path when building Dart on Windows.

tools/utils.py

 # Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 # This file contains a set of utilities functions used by other Python-based
 # scripts.
 
 import commands
 import os
 import platform
@@ skipping 42 matching lines @@
 def GuessCpus():
   if os.path.exists("/proc/cpuinfo"):
     return int(commands.getoutput("grep -E '^processor' /proc/cpuinfo | wc -l"))
   if os.path.exists("/usr/bin/hostinfo"):
     return int(commands.getoutput('/usr/bin/hostinfo | grep "processors are logically available." | awk "{ print \$1 }"'))
   win_cpu_count = os.getenv("NUMBER_OF_PROCESSORS")
   if win_cpu_count:
     return int(win_cpu_count)
   return int(os.getenv("DART_NUMBER_OF_CORES", 2))
 
+def GetWindowsRegistryKeyName(name):
+  import win32process
+  # Check if python process is 64-bit or if it's 32-bit running in 64-bit OS.
+  # We need to know whether host is 64-bit so that we are looking in right
+  # registry for Visual Studio path.
+  if sys.maxsize > 2**32 or win32process.IsWow64Process():
+    wow6432Node = 'Wow6432Node\\'
+  else:
+    wow6432Node = ''
+  return r'SOFTWARE\%s%s' % (wow6432Node, name)
+
+# Try to guess Visual Studio location when buiding on Windows.
+def GuessVisualStudioPath():
+  defaultPath = r"C:\Program Files (x86)\Microsoft Visual Studio 10.0\Common7" \
+                r"\IDE"
+  defaultExecutable = "devenv.com"
+
+  if not IsWindows():
+    return (defaultPath, defaultExecutable)
+
+  keyNamesAndExecutables = [
+    # Pair for non-Express editions.
+    (GetWindowsRegistryKeyName(r'Microsoft\VisualStudio'), 'devenv.com'),
+    # Pair for 2012 Express edition.
+    (GetWindowsRegistryKeyName(r'Microsoft\VSWinExpress'), 'VSWinExpress.exe'),
+    # Pair for pre-2012 Express editions.
+    (GetWindowsRegistryKeyName(r'Microsoft\VCExpress'), 'VCExpress.exe')]
+
+  bestGuess = (None, (defaultPath, defaultExecutable))
+
+  import _winreg
+  for (keyName, executable) in keyNamesAndExecutables:
+    try:
+      key = _winreg.OpenKey(_winreg.HKEY_LOCAL_MACHINE, keyName)
+    except WindowsError:
+      # Can't find this key - moving on the next one.
+      continue
+
+    try:
+      subkeyCounter = 0
+      while True:
+        try:
+          subkeyName = _winreg.EnumKey(key, subkeyCounter)
+          subkeyCounter = subkeyCounter + 1
+        except WindowsError:
+          # Reached end of enumeration. Moving on the next key.
+          break
+
+        match = re.match(r'^\d+\.\d+$', subkeyName)
+        if match:
+          with _winreg.OpenKey(key, subkeyName) as subkey:
+            try:
+              (installDir, registrytype) = _winreg.QueryValueEx(subkey,
+                                                                'InstallDir')
+            except WindowsError:
+              # Can't find value under the key - continue to the next key.
+              continue
+            isExpress = executable != 'devenv.com'
+            if not isExpress and subkeyName == '10.0':
+              # Stop search since if we found non-Express VS2010 version
+              # installed, which is preferred version.
+              return (installDir, executable)
+            else:
+              version = float(subkeyName)
+              # We prefer higher version of Visual Studio and given equal
+              # version numbers we prefer non-Express edition.
+              if version > bestGuess[0]:

[kustermann, 2013/02/19 08:38:23]

The first time we hit this comparision, we compare 'version' with None. Although
this works in python versions 2.X, it is not optimal (it will raise an exception
in python3 AFAIK).
You can keep it, but you could also do
bestGuess  = (0.0, (defaultPath, defaultExecutable))
on line 91.

[aam-me, 2013/02/19 11:58:53]

Done. Thanks, didn't know that.

+                bestGuess = (version, (installDir, executable))
+    finally:
+      _winreg.CloseKey(key)
+  return bestGuess[1]
+
 
 # Returns true if we're running under Windows.
 def IsWindows():
   return GuessOS() == 'win32'
 
 
 # Reads a text file into an array of strings - one for each
 # line. Strips comments in the process.
 def ReadLinesFrom(name):
   result = []
@@ skipping 191 matching lines @@
     os.unlink(name)
   except OSError, e:
     PrintError("os.unlink() " + str(e))
 
 
 def Main(argv):
   print "GuessOS() -> ", GuessOS()
   print "GuessArchitecture() -> ", GuessArchitecture()
   print "GuessCpus() -> ", GuessCpus()
   print "IsWindows() -> ", IsWindows()
+  print "GuessVisualStudioPath() -> ", GuessVisualStudioPath()
 
 
 class Error(Exception):
   pass
 
 
 class ToolError(Exception):
   """Deprecated exception, use Error instead."""
 
   def __init__(self, value):
@@ skipping 37 matching lines @@
 
 def DartSdkBinary():
   tools_dir = os.path.dirname(os.path.realpath(__file__))
   dart_binary_prefix = os.path.join(tools_dir, '..', 'sdk' , 'bin')
   return os.path.join(dart_binary_prefix, 'dart')
 
 
 if __name__ == "__main__":
   import sys
   Main(sys.argv)