swc-windows-installer.py: Force UNIX-style \n line endings for ~/nano.rc

On Thu, Mar 13, 2014 at 03:37:12AM -0700, Ethan White wrote [1]:
> We now have a line ending issue resulting in:
>
>     Error reading /cygdrive/c/Users/...
>
> This is fixed by running `dos2unix` on the resulting nano.rc.

This is also mentioned in the nano FAQ [2]:

> Note that the nano.rc file must remain Unix formated in order for
> nano to unerstand it.

Since Python 3.0 and PEP 3116, Python's open() has taken a 'newline'
argument that allows you to override the default line separator for a
particular file [3,4].  However, Python 2.x does not support that
argument [5].  This commit adds a local 'open3' which uses a terrible
hack of a wrapper on Python 2 to fake that support.  It opens the file
in binary mode, and takes advantage of Python 2's lack of distinction
between str and bytes to treat the \n-terminated strings as the raw
binary output.  That's going to crash and burn if you have any
non-ASCII characters in the output content, but we explicitly set all
the components in our relative include_path, so that shouldn't be a
problem.

Another side effect of binary-mode is that we are going to get
ASCII-encoded output, not output encoded in the user's preferred
encoding (locale.getpreferredencoding [3,6]).  That's unfortunate,
because nano does the right thing and uses your locale to decode input
(at least for UTF-8 locales [7], presumably including your nano.rc
file).

[1]: https://github.com/swcarpentry/bc/pull/357#issuecomment-37518899
[2]: http://www.nano-editor.org/dist/v2.2/faq.html#3.9.1
[3]: http://docs.python.org/3/library/functions.html#open
[4]: http://legacy.python.org/dev/peps/pep-3116/
[5]: http://docs.python.org/2/library/functions.html#open
[6]: http://docs.python.org/2/library/stdtypes.html#file.encoding
[7]: http://www.nano-editor.org/dist/v2.2/faq.html#5.3

diff --git a/swc-windows-installer.py b/swc-windows-installer.py
index 3fee89343a4ff061343e683bf80c90661e81e94b..b305138b7f73ff4b98e142dbabeeb03cc2078f11 100755 (executable)
--- a/swc-windows-installer.py
+++ b/swc-windows-installer.py
@@ -28,6 +28,7 @@ except ImportError:  # Python 2
     from StringIO import StringIO as _BytesIO
 import os
 import re
+import sys
 import tarfile
 try:  # Python 3
     from urllib.request import urlopen as _urlopen
@@ -36,6 +37,19 @@ except ImportError:  # Python 2
 import zipfile
 
 
+if sys.version_info >= (3, 0):  # Python 3
+    open3 = open
+else:
+    def open3(file, mode='r', newline=None):
+        if newline:
+            if newline != '\n':
+                raise NotImplementedError(newline)
+            f = open(file, mode + 'b')
+        else:
+            f = open(file, mode)
+        return f
+
+
 def download(url, sha1):
     """Download a file and verify it's hash"""
     r = _urlopen(url)
@@ -127,7 +141,7 @@ def install_nanorc(install_directory):
     nanorc = os.path.join(home, 'nano.rc')
     if not os.path.isfile(nanorc):
         syntax_dir = os.path.join(install_directory, 'doc', 'syntax')
-        with open(nanorc, 'w') as f:
+        with open3(nanorc, 'w', newline='\n') as f:
             for filename in os.listdir(syntax_dir):
                 if filename.endswith('.nanorc'):
                     path = os.path.join(syntax_dir, filename)