Fix quoting shell args on Windows

pylib/gyp/msvs_emulation.py

+# Copyright (c) 2012 Google Inc. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+

[Nico, 2012/02/20 23:17:49]

Needs module docstring

[scottmg, 2012/02/21 00:14:44]

Done.

+import re
+
+windows_quoter_regex = re.compile(r'(\\*)"')
+
+def QuoteCmdExeArgument(arg):

[Nico, 2012/02/20 23:17:49]

need function docstring

[scottmg, 2012/02/21 00:14:44]

Done.

+  # See http://goo.gl/cuFbX and http://goo.gl/dhPnp including the comment

[Nico, 2012/02/20 23:17:49]

nit: I wouldn't use a URL shortener

[scottmg, 2012/02/21 00:14:44]

The urls were longer than 80 so it looked yucky.

+  # threads. This is actually the quoting rules for CommandLineToArgvW, not
+  # for the shell, because the shell doesn't do anything in Windows. This
+  # works more or less because most programs (including the compiler, etc.)
+  # use that function to handle command line arguments.
+  #
+  # For a literal quote, CommandLineToArgvW requires 2n+1 backslashes
+  # preceding it, and results in n backslashes + the quote. So we substitute
+  # in 2* what we match, +1 more, plus the quote.
+  tmp = windows_quoter_regex.sub(lambda mo: 2 * mo.group(1) + '\\"', arg)
+
+  # Now, we need to escape some things that are actually for the shell. %'s

[Nico, 2012/02/20 23:17:49]

The '%' handling happens further down, so I wouldn't mention it in this comment.

[scottmg, 2012/02/21 00:14:44]

Done.

+  # need to be doubled, and various other characters need to be ^ escaped.
+  tmp = re.sub(r'([&|^])', r'^\1', tmp)
+
+  # Also make sure to escape the % so that they're passed literally through
+  # escaping so they can be singled to just the original %. Otherwise, trying
+  # to pass the literal representation that looks like an environment variable
+  # to the shell (e.g. %PATH%) would fail.
+  tmp = tmp.replace('%', '^%^%')
+
+  # Finally, wrap the whole thing in quotes so that the above quote rule
+  # applies and whitespace isn't a word break.
+  return '"' + tmp + '"'

[Nico, 2012/02/20 23:17:49]

I assume all this is covered by existing tests.

[scottmg, 2012/02/21 00:14:44]

Yes, this change is just trying to get existing tests working
("defines-escaping" is pretty thorough). I'll add new tests if I find other
things that aren't tested, as I get farther.