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

tools/utils.py

Index: tools/utils.py
diff --git a/tools/utils.py b/tools/utils.py
index c1305b598d076f38c15ca5170d266ab0f906f86a..e2094694240f8acaa8a05c6025e279cb9f46f0ce 100644
--- a/tools/utils.py
+++ b/tools/utils.py
@@ -60,12 +60,53 @@ def GuessCpus():
     return int(win_cpu_count)
   return int(os.getenv("DART_NUMBER_OF_CORES", 2))
 
+# Try to guess Visual Studio location when buiding on Windows.
+def GuessVisualStudioPath():
+  defaultPath = 'C:\\Program Files (x86)\\Microsoft Visual Studio 10.0\\Common7'
+  '\\IDE'
+  if IsWindows():

[ahe, 2013/02/18 15:47:20]

if not IsWindows():
  return defaultPath

Then the rest doesn't need to be indented.

[aam-me, 2013/02/18 16:20:06]

Done.

+    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 = ""
+
+    import _winreg
+    try:
+      key = _winreg.OpenKey(_winreg.HKEY_LOCAL_MACHINE,
+                           "SOFTWARE\\" + wow6432Node + "Microsoft\\VisualStudio")

[ahe, 2013/02/18 15:47:20]

Long line. Also, I think our Python style guide prefer using % rather than
string concatenation with +. So this should be:

"SOFTWARE\\%sMicrosoft\\VisualStudio" % wow6432Node

[aam-me, 2013/02/18 16:20:06]

Done.

+    except WindowsError:

[ahe, 2013/02/18 15:47:20]

Please document why it is OK to ignore this error.

[aam-me, 2013/02/18 16:20:06]

Done.

+      return defaultPath
+
+    iSubkey = 0

[ahe, 2013/02/18 15:47:20]

What does this variable mean? The word "iSubkey" is a bit strange.

[aam-me, 2013/02/18 16:20:06]

This is subkey counter. Changed name.

+    while(True):

[ahe, 2013/02/18 15:47:20]

I don't think you need parentheses here in Python.

[aam-me, 2013/02/18 16:20:06]

Done.

+      try:
+        subkeyName = _winreg.EnumKey(key, iSubkey)
+      except WindowsError:
+        # Reached end of enumeration

[ahe, 2013/02/18 15:47:20]

Is there a way to check, or must you catch an exception?

[aam-me, 2013/02/18 16:20:06]

According to http://docs.python.org/2/library/_winreg.html#_winreg.EnumKey I
have to catch exception, unfortunately.

+        return defaultPath
+      match = re.match('^(\\d+\\.\\d+)$', subkeyName)
+      if not match is None:

[ahe, 2013/02/18 15:47:20]

if match:

[aam-me, 2013/02/18 16:20:06]

Done.

+        with _winreg.OpenKey(key, subkeyName) as subkey:
+          try:
+            (path, registrytype) = _winreg.QueryValueEx(subkey, 'InstallDir')
+            return path
+          except WindowsError:
+            # Can't find value under the key - continue to the next key
+            pass
+      iSubkey = iSubkey + 1
+
+    _winreg.CloseKey(key)

[ahe, 2013/02/18 15:47:20]

This is dead code as it comes after an "infinite" loop.

[aam-me, 2013/02/18 16:20:06]

Thanks. Wrapped it into try: finally: to close the key.

+  else:
+    return defaultPath
 
 # 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):
@@ -271,6 +312,7 @@ def Main(argv):
   print "GuessArchitecture() -> ", GuessArchitecture()
   print "GuessCpus() -> ", GuessCpus()
   print "IsWindows() -> ", IsWindows()
+  print "GuessVisualStudioPath() -> ", GuessVisualStudioPath()
 
 
 class Error(Exception):