Make subprocess2.Popen a class instead of a function.

subprocess2.py

 # coding=utf8
 # Copyright (c) 2011 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 """Collection of subprocess wrapper functions.
 
 In theory you shouldn't need anything else in subprocess, or this module failed.
 """
 
 from __future__ import with_statement
@@ skipping 113 matching lines @@
   # Requires modifications.
   env = env.copy()
   def fix_lang(name):
     if not is_english(name):
       env[name] = 'en_US.UTF-8'
   fix_lang('LANG')
   fix_lang('LANGUAGE')
   return env
 
 
-def Popen(args, **kwargs):
+class Popen(subprocess.Popen):
   """Wraps subprocess.Popen() with various workarounds.
 
-  Returns a subprocess.Popen object.
-
   - Forces English output since it's easier to parse the stdout if it is always
     in English.
   - Sets shell=True on windows by default. You can override this by forcing
     shell parameter to a value.
   - Adds support for VOID to not buffer when not needed.
 
   Note: Popen() can throw OSError when cwd or args[0] doesn't exist. Translate
   exceptions generated by cygwin when it fails trying to emulate fork().
   """
-  # Make sure we hack subprocess if necessary.
-  hack_subprocess()
-  add_kill()
+  def __init__(self, args, **kwargs):
+    # Make sure we hack subprocess if necessary.
+    hack_subprocess()
+    add_kill()
 
-  env = get_english_env(kwargs.get('env'))
-  if env:
-    kwargs['env'] = env
-  if kwargs.get('shell') is None:
-    # *Sigh*:  Windows needs shell=True, or else it won't search %PATH% for the
-    # executable, but shell=True makes subprocess on Linux fail when it's called
-    # with a list because it only tries to execute the first item in the list.
-    kwargs['shell'] = bool(sys.platform=='win32')
+    env = get_english_env(kwargs.get('env'))
+    if env:
+      kwargs['env'] = env
+    if kwargs.get('shell') is None:
+      # *Sigh*:  Windows needs shell=True, or else it won't search %PATH% for
+      # the executable, but shell=True makes subprocess on Linux fail when it's
+      # called with a list because it only tries to execute the first item in
+      # the list.
+      kwargs['shell'] = bool(sys.platform=='win32')
 
-  if isinstance(args, basestring):
-    tmp_str = args
-  elif isinstance(args, (list, tuple)):
-    tmp_str = ' '.join(args)
-  else:
-    raise CalledProcessError(None, args, kwargs.get('cwd'), None, None)
-  if kwargs.get('cwd', None):
-    tmp_str += ';  cwd=%s' % kwargs['cwd']
-  logging.debug(tmp_str)
+    if isinstance(args, basestring):
+      tmp_str = args
+    elif isinstance(args, (list, tuple)):
+      tmp_str = ' '.join(args)
+    else:
+      raise CalledProcessError(None, args, kwargs.get('cwd'), None, None)
+    if kwargs.get('cwd', None):
+      tmp_str += ';  cwd=%s' % kwargs['cwd']
+    logging.debug(tmp_str)
 
-  def fix(stream):
-    if kwargs.get(stream) in (VOID, os.devnull):
-      # Replaces VOID with handle to /dev/null.
-      # Create a temporary file to workaround python's deadlock.
-      # http://docs.python.org/library/subprocess.html#subprocess.Popen.wait
-      # When the pipe fills up, it will deadlock this process. Using a real file
-      # works around that issue.
-      kwargs[stream] = open(os.devnull, 'w')
+    def fix(stream):
+      if kwargs.get(stream) in (VOID, os.devnull):
+        # Replaces VOID with handle to /dev/null.
+        # Create a temporary file to workaround python's deadlock.
+        # http://docs.python.org/library/subprocess.html#subprocess.Popen.wait
+        # When the pipe fills up, it will deadlock this process. Using a real
+        # file works around that issue.
+        kwargs[stream] = open(os.devnull, 'w')
 
-  fix('stdout')
-  fix('stderr')
+    fix('stdout')
+    fix('stderr')
 
-  try:
-    return subprocess.Popen(args, **kwargs)
-  except OSError, e:
-    if e.errno == errno.EAGAIN and sys.platform == 'cygwin':
-      # Convert fork() emulation failure into a CygwinRebaseError().
-      raise CygwinRebaseError(
-          e.errno,
-          args,
-          kwargs.get('cwd'),
-          None,
-          'Visit '
-          'http://code.google.com/p/chromium/wiki/CygwinDllRemappingFailure to '
-          'learn how to fix this error; you need to rebase your cygwin dlls')
-    # Popen() can throw OSError when cwd or args[0] doesn't exist. Let it go
-    # through
-    raise
+    try:
+      super(Popen, self).__init__(args, **kwargs)
+    except OSError, e:
+      if e.errno == errno.EAGAIN and sys.platform == 'cygwin':
+        # Convert fork() emulation failure into a CygwinRebaseError().
+        raise CygwinRebaseError(
+            e.errno,
+            args,
+            kwargs.get('cwd'),
+            None,
+            'Visit '
+            'http://code.google.com/p/chromium/wiki/CygwinDllRemappingFailure '
+            'to learn how to fix this error; you need to rebase your cygwin '
+            'dlls')
+      # Popen() can throw OSError when cwd or args[0] doesn't exist. Let it go
+      # through
+      raise
 
 
 def communicate(args, timeout=None, **kwargs):
   """Wraps subprocess.Popen().communicate().
 
   Returns ((stdout, stderr), returncode).
 
   - The process will be killed after |timeout| seconds and returncode set to
     TIMED_OUT.
   - Automatically passes stdin content as input so do not specify stdin=PIPE.
@@ skipping 92 matching lines @@
 
   Captures stdout of a process call and returns stdout only.
 
   - Throws if return code is not 0.
   - Works even prior to python 2.7.
   - Blocks stdin by default if not specified since no output will be visible.
   - As per doc, "The stdout argument is not allowed as it is used internally."
   """
   kwargs.setdefault('stdin', VOID)
   return check_call_out(args, stdout=PIPE, **kwargs)[0]