Make subprocess2.Popen a class instead of a function.

This will be necessary to override member functions eventually. It also better
replicates what subprocess.Popen is.

R=dpranke@chromium.org
BUG=
TEST=


Review URL: http://codereview.chromium.org/8570005

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@111530 0039d316-1c4b-4281-b951-d872f2087c98

subprocess2.py

@@ -131,11 +131,9 @@ def get_english_env(env):
   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
@@ -145,57 +143,60 @@ def Popen(args, **kwargs):
   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()
-
-  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)
-
-  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')
-
-  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
+  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')
+
+    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')
+
+    fix('stdout')
+    fix('stderr')
+
+    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):

tests/subprocess2_test.py

@@ -47,7 +47,7 @@ class DefaultsTest(unittest.TestCase):
   TO_SAVE = {
     subprocess2: [
       'Popen', 'communicate', 'call', 'check_call', 'capture', 'check_output'],
-    subprocess2.subprocess: ['Popen'],
+    subprocess2.subprocess.Popen: ['__init__', 'communicate'],
   }
 
   def setUp(self):
@@ -65,17 +65,19 @@ class DefaultsTest(unittest.TestCase):
 
   @staticmethod
   def _fake_communicate():
+    """Mocks subprocess2.communicate()."""
     results = {}
     def fake_communicate(args, **kwargs):
       assert not results
       results.update(kwargs)
       results['args'] = args
-      return ['stdout', 'stderr'], 0
+      return ('stdout', 'stderr'), 0
     subprocess2.communicate = fake_communicate
     return results
 
   @staticmethod
   def _fake_Popen():
+    """Mocks the whole subprocess2.Popen class."""
     results = {}
     class fake_Popen(object):
       returncode = -8
@@ -91,23 +93,22 @@ class DefaultsTest(unittest.TestCase):
 
   @staticmethod
   def _fake_subprocess_Popen():
+    """Mocks the base class subprocess.Popen only."""
     results = {}
-    class fake_Popen(object):
-      returncode = -8
-      def __init__(self, args, **kwargs):
-        assert not results
-        results.update(kwargs)
-        results['args'] = args
-      @staticmethod
-      def communicate():
-        return None, None
-    subprocess2.subprocess.Popen = fake_Popen
+    def __init__(self, args, **kwargs):
+      assert not results
+      results.update(kwargs)
+      results['args'] = args
+    def communicate():
+      return None, None
+    subprocess2.subprocess.Popen.__init__ = __init__
+    subprocess2.subprocess.Popen.communicate = communicate
     return results
 
   def test_check_call_defaults(self):
     results = self._fake_communicate()
     self.assertEquals(
-        ['stdout', 'stderr'], subprocess2.check_call_out(['foo'], a=True))
+        ('stdout', 'stderr'), subprocess2.check_call_out(['foo'], a=True))
     expected = {
         'args': ['foo'],
         'a':True,
@@ -139,7 +140,12 @@ class DefaultsTest(unittest.TestCase):
   def test_Popen_defaults(self):
     results = self._fake_subprocess_Popen()
     proc = subprocess2.Popen(['foo'], a=True)
-    self.assertEquals(-8, proc.returncode)
+    # Cleanup code in subprocess.py needs this member to be set.
+    # pylint: disable=W0201
+    proc._child_created = None
+    # Since subprocess.Popen.__init__() is not called, proc.returncode shouldn't
+    # be present.
+    self.assertFalse(hasattr(proc, 'returncode'))
     expected = {
         'args': ['foo'],
         'a': True,