Split init / exec of tmux_cmd for debuggability

tmux_cmd initialization composes the command

the command will be available in the instance attribute
.cmd

.execute() instance method will run tmux_cmd

see Server.cmd for example of new usage

Related #77

libtmux/common.py

@@ -161,7 +161,12 @@ class tmux_cmd(object):
 
     .. code-block:: python
 
-        proc = tmux_cmd('new-session', '-s%' % 'my session')
+        c = tmux_cmd('new-session', '-s%' % 'my session')
+
+        # You can actually see the command in the .cmd attribute
+        print(c.cmd)
+
+        proc = c.execute()
 
         if proc.stderr:
             raise exc.LibTmuxException(
@@ -201,6 +206,8 @@ def __init__(self, *args, **kwargs):
 
         self.cmd = cmd
 
+    def execute(self):
+        cmd = self.cmd
         try:
             self.process = subprocess.Popen(
                 cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE
@@ -229,6 +236,7 @@ def __init__(self, *args, **kwargs):
                 self.stdout = self.stderr[0]
 
         logger.debug('self.stdout for %s: \n%s' % (' '.join(cmd), self.stdout))
+        return self
 
 
 class TmuxMappingObject(MutableMapping):
@@ -455,7 +463,7 @@ def get_version():
     :class:`distutils.version.LooseVersion`
         tmux version according to :func:`libtmux.common.which`'s tmux
     """
-    proc = tmux_cmd('-V')
+    proc = tmux_cmd('-V').execute()
     if proc.stderr:
         if proc.stderr[0] == 'tmux: unknown option -- V':
             if sys.platform.startswith("openbsd"):  # openbsd has no tmux -V

libtmux/server.py

@@ -126,7 +126,7 @@ def cmd(self, *args, **kwargs):
             else:
                 raise ValueError('Server.colors must equal 88 or 256')
 
-        return tmux_cmd(*args, **kwargs)
+        return tmux_cmd(*args, **kwargs).execute()
 
     def _list_sessions(self):
         """

tests/test_common.py

@@ -33,6 +33,9 @@ class Hi(object):
             stdout = ['tmux master']
             stderr = None
 
+            def execute(self):
+                return self
+
         return Hi()
 
     monkeypatch.setattr(libtmux.common, 'tmux_cmd', mock_tmux_cmd)
@@ -51,6 +54,9 @@ class Hi(object):
             stdout = ['tmux next-2.9']
             stderr = None
 
+            def execute(self):
+                return self
+
         return Hi()
 
     monkeypatch.setattr(libtmux.common, 'tmux_cmd', mock_tmux_cmd)
@@ -66,6 +72,9 @@ def mock_tmux_cmd(param):
         class Hi(object):
             stderr = ['tmux: unknown option -- V']
 
+            def execute(self):
+                return self
+
         return Hi()
 
     monkeypatch.setattr(libtmux.common, 'tmux_cmd', mock_tmux_cmd)
@@ -83,6 +92,9 @@ def mock_tmux_cmd(param):
         class Hi(object):
             stderr = ['tmux: unknown option -- V']
 
+            def execute(self):
+                return self
+
         return Hi()
 
     monkeypatch.setattr(libtmux.common, 'tmux_cmd', mock_tmux_cmd)
@@ -183,6 +195,12 @@ def test_tmux_cmd_unicode(session):
     session.cmd('new-window', '-t', 3, '-n', 'юникод', '-F', u'Ελληνικά')
 
 
+def test_tmux_cmd_makes_cmd_available():
+    """tmux_cmd objects should make .cmd attribute available."""
+    command = tmux_cmd('-V')
+    assert hasattr(command, 'cmd')
+
+
 @pytest.mark.parametrize(
     "session_name,raises,exc_msg_regex",
     [