3055 class ctxmanager(object):

  3056     '''A context manager for use in 'with' blocks to allow multiple

  3057     contexts to be entered at once.  This is both safer and more

  3058     flexible than contextlib.nested.

  3059 

  3060     Once Mercurial supports Python 2.7+, this will become mostly

  3061     unnecessary.

  3062     '''

  3063 

  3064     def __init__(self, *args):

  3065         '''Accepts a list of no-argument functions that return context

  3066         managers.  These will be invoked at __call__ time.'''

  3067         self._pending = args

  3068         self._atexit = []

  3069 

  3070     def __enter__(self):

  3071         return self

  3072 

  3073     def enter(self):

  3074         '''Create and enter context managers in the order in which they were

  3075         passed to the constructor.'''

  3076         values = []

  3077         for func in self._pending:

  3078             obj = func()

  3079             values.append(obj.__enter__())

  3080             self._atexit.append(obj.__exit__)

  3081         del self._pending

  3082         return values

  3083 

  3084     def atexit(self, func, *args, **kwargs):

  3085         '''Add a function to call when this context manager exits.  The

  3086         ordering of multiple atexit calls is unspecified, save that

  3087         they will happen before any __exit__ functions.'''

  3088         def wrapper(exc_type, exc_val, exc_tb):

  3089             func(*args, **kwargs)

  3090         self._atexit.append(wrapper)

  3091         return func

  3092 

  3093     def __exit__(self, exc_type, exc_val, exc_tb):

  3094         '''Context managers are exited in the reverse order from which

  3095         they were created.'''

  3096         received = exc_type is not None

  3097         suppressed = False

  3098         pending = None

  3099         self._atexit.reverse()

  3100         for exitfunc in self._atexit:

  3101             try:

  3102                 if exitfunc(exc_type, exc_val, exc_tb):

  3103                     suppressed = True

  3104                     exc_type = None

  3105                     exc_val = None

  3106                     exc_tb = None

  3107             except BaseException:

  3108                 pending = sys.exc_info()

  3109                 exc_type, exc_val, exc_tb = pending = sys.exc_info()

  3110         del self._atexit

  3111         if pending:

  3112             raise exc_val

  3113         return received and suppressed

  3114