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stbi/Lib/site-packages/pip/_vendor/contextlib2.py

+"""contextlib2 - backports and enhancements to the contextlib module"""
+
+import abc
+import sys
+import warnings
+from collections import deque
+from functools import wraps
+
+__all__ = ["contextmanager", "closing", "nullcontext",
+           "AbstractContextManager",
+           "ContextDecorator", "ExitStack",
+           "redirect_stdout", "redirect_stderr", "suppress"]
+
+# Backwards compatibility
+__all__ += ["ContextStack"]
+
+
+# Backport abc.ABC
+if sys.version_info[:2] >= (3, 4):
+    _abc_ABC = abc.ABC
+else:
+    _abc_ABC = abc.ABCMeta('ABC', (object,), {'__slots__': ()})
+
+
+# Backport classic class MRO
+def _classic_mro(C, result):
+    if C in result:
+        return
+    result.append(C)
+    for B in C.__bases__:
+        _classic_mro(B, result)
+    return result
+
+
+# Backport _collections_abc._check_methods
+def _check_methods(C, *methods):
+    try:
+        mro = C.__mro__
+    except AttributeError:
+        mro = tuple(_classic_mro(C, []))
+
+    for method in methods:
+        for B in mro:
+            if method in B.__dict__:
+                if B.__dict__[method] is None:
+                    return NotImplemented
+                break
+        else:
+            return NotImplemented
+    return True
+
+
+class AbstractContextManager(_abc_ABC):
+    """An abstract base class for context managers."""
+
+    def __enter__(self):
+        """Return `self` upon entering the runtime context."""
+        return self
+
+    @abc.abstractmethod
+    def __exit__(self, exc_type, exc_value, traceback):
+        """Raise any exception triggered within the runtime context."""
+        return None
+
+    @classmethod
+    def __subclasshook__(cls, C):
+        """Check whether subclass is considered a subclass of this ABC."""
+        if cls is AbstractContextManager:
+            return _check_methods(C, "__enter__", "__exit__")
+        return NotImplemented
+
+
+class ContextDecorator(object):
+    """A base class or mixin that enables context managers to work as decorators."""
+
+    def refresh_cm(self):
+        """Returns the context manager used to actually wrap the call to the
+        decorated function.
+
+        The default implementation just returns *self*.
+
+        Overriding this method allows otherwise one-shot context managers
+        like _GeneratorContextManager to support use as decorators via
+        implicit recreation.
+
+        DEPRECATED: refresh_cm was never added to the standard library's
+                    ContextDecorator API
+        """
+        warnings.warn("refresh_cm was never added to the standard library",
+                      DeprecationWarning)
+        return self._recreate_cm()
+
+    def _recreate_cm(self):
+        """Return a recreated instance of self.
+
+        Allows an otherwise one-shot context manager like
+        _GeneratorContextManager to support use as
+        a decorator via implicit recreation.
+
+        This is a private interface just for _GeneratorContextManager.
+        See issue #11647 for details.
+        """
+        return self
+
+    def __call__(self, func):
+        @wraps(func)
+        def inner(*args, **kwds):
+            with self._recreate_cm():
+                return func(*args, **kwds)
+        return inner
+
+
+class _GeneratorContextManager(ContextDecorator):
+    """Helper for @contextmanager decorator."""
+
+    def __init__(self, func, args, kwds):
+        self.gen = func(*args, **kwds)
+        self.func, self.args, self.kwds = func, args, kwds
+        # Issue 19330: ensure context manager instances have good docstrings
+        doc = getattr(func, "__doc__", None)
+        if doc is None:
+            doc = type(self).__doc__
+        self.__doc__ = doc
+        # Unfortunately, this still doesn't provide good help output when
+        # inspecting the created context manager instances, since pydoc
+        # currently bypasses the instance docstring and shows the docstring
+        # for the class instead.
+        # See http://bugs.python.org/issue19404 for more details.
+
+    def _recreate_cm(self):
+        # _GCM instances are one-shot context managers, so the
+        # CM must be recreated each time a decorated function is
+        # called
+        return self.__class__(self.func, self.args, self.kwds)
+
+    def __enter__(self):
+        try:
+            return next(self.gen)
+        except StopIteration:
+            raise RuntimeError("generator didn't yield")
+
+    def __exit__(self, type, value, traceback):
+        if type is None:
+            try:
+                next(self.gen)
+            except StopIteration:
+                return
+            else:
+                raise RuntimeError("generator didn't stop")
+        else:
+            if value is None:
+                # Need to force instantiation so we can reliably
+                # tell if we get the same exception back
+                value = type()
+            try:
+                self.gen.throw(type, value, traceback)
+                raise RuntimeError("generator didn't stop after throw()")
+            except StopIteration as exc:
+                # Suppress StopIteration *unless* it's the same exception that
+                # was passed to throw().  This prevents a StopIteration
+                # raised inside the "with" statement from being suppressed.
+                return exc is not value
+            except RuntimeError as exc:
+                # Don't re-raise the passed in exception
+                if exc is value:
+                    return False
+                # Likewise, avoid suppressing if a StopIteration exception
+                # was passed to throw() and later wrapped into a RuntimeError
+                # (see PEP 479).
+                if _HAVE_EXCEPTION_CHAINING and exc.__cause__ is value:
+                    return False
+                raise
+            except:
+                # only re-raise if it's *not* the exception that was
+                # passed to throw(), because __exit__() must not raise
+                # an exception unless __exit__() itself failed.  But throw()
+                # has to raise the exception to signal propagation, so this
+                # fixes the impedance mismatch between the throw() protocol
+                # and the __exit__() protocol.
+                #
+                if sys.exc_info()[1] is not value:
+                    raise
+
+
+def contextmanager(func):
+    """@contextmanager decorator.
+
+    Typical usage:
+
+        @contextmanager
+        def some_generator(<arguments>):
+            <setup>
+            try:
+                yield <value>
+            finally:
+                <cleanup>
+
+    This makes this:
+
+        with some_generator(<arguments>) as <variable>:
+            <body>
+
+    equivalent to this:
+
+        <setup>
+        try:
+            <variable> = <value>
+            <body>
+        finally:
+            <cleanup>
+
+    """
+    @wraps(func)
+    def helper(*args, **kwds):
+        return _GeneratorContextManager(func, args, kwds)
+    return helper
+
+
+class closing(object):
+    """Context to automatically close something at the end of a block.
+
+    Code like this:
+
+        with closing(<module>.open(<arguments>)) as f:
+            <block>
+
+    is equivalent to this:
+
+        f = <module>.open(<arguments>)
+        try:
+            <block>
+        finally:
+            f.close()
+
+    """
+    def __init__(self, thing):
+        self.thing = thing
+
+    def __enter__(self):
+        return self.thing
+
+    def __exit__(self, *exc_info):
+        self.thing.close()
+
+
+class _RedirectStream(object):
+
+    _stream = None
+
+    def __init__(self, new_target):
+        self._new_target = new_target
+        # We use a list of old targets to make this CM re-entrant
+        self._old_targets = []
+
+    def __enter__(self):
+        self._old_targets.append(getattr(sys, self._stream))
+        setattr(sys, self._stream, self._new_target)
+        return self._new_target
+
+    def __exit__(self, exctype, excinst, exctb):
+        setattr(sys, self._stream, self._old_targets.pop())
+
+
+class redirect_stdout(_RedirectStream):
+    """Context manager for temporarily redirecting stdout to another file.
+
+        # How to send help() to stderr
+        with redirect_stdout(sys.stderr):
+            help(dir)
+
+        # How to write help() to a file
+        with open('help.txt', 'w') as f:
+            with redirect_stdout(f):
+                help(pow)
+    """
+
+    _stream = "stdout"
+
+
+class redirect_stderr(_RedirectStream):
+    """Context manager for temporarily redirecting stderr to another file."""
+
+    _stream = "stderr"
+
+
+class suppress(object):
+    """Context manager to suppress specified exceptions
+
+    After the exception is suppressed, execution proceeds with the next
+    statement following the with statement.
+
+         with suppress(FileNotFoundError):
+             os.remove(somefile)
+         # Execution still resumes here if the file was already removed
+    """
+
+    def __init__(self, *exceptions):
+        self._exceptions = exceptions
+
+    def __enter__(self):
+        pass
+
+    def __exit__(self, exctype, excinst, exctb):
+        # Unlike isinstance and issubclass, CPython exception handling
+        # currently only looks at the concrete type hierarchy (ignoring
+        # the instance and subclass checking hooks). While Guido considers
+        # that a bug rather than a feature, it's a fairly hard one to fix
+        # due to various internal implementation details. suppress provides
+        # the simpler issubclass based semantics, rather than trying to
+        # exactly reproduce the limitations of the CPython interpreter.
+        #
+        # See http://bugs.python.org/issue12029 for more details
+        return exctype is not None and issubclass(exctype, self._exceptions)
+
+
+# Context manipulation is Python 3 only
+_HAVE_EXCEPTION_CHAINING = sys.version_info[0] >= 3
+if _HAVE_EXCEPTION_CHAINING:
+    def _make_context_fixer(frame_exc):
+        def _fix_exception_context(new_exc, old_exc):
+            # Context may not be correct, so find the end of the chain
+            while 1:
+                exc_context = new_exc.__context__
+                if exc_context is old_exc:
+                    # Context is already set correctly (see issue 20317)
+                    return
+                if exc_context is None or exc_context is frame_exc:
+                    break
+                new_exc = exc_context
+            # Change the end of the chain to point to the exception
+            # we expect it to reference
+            new_exc.__context__ = old_exc
+        return _fix_exception_context
+
+    def _reraise_with_existing_context(exc_details):
+        try:
+            # bare "raise exc_details[1]" replaces our carefully
+            # set-up context
+            fixed_ctx = exc_details[1].__context__
+            raise exc_details[1]
+        except BaseException:
+            exc_details[1].__context__ = fixed_ctx
+            raise
+else:
+    # No exception context in Python 2
+    def _make_context_fixer(frame_exc):
+        return lambda new_exc, old_exc: None
+
+    # Use 3 argument raise in Python 2,
+    # but use exec to avoid SyntaxError in Python 3
+    def _reraise_with_existing_context(exc_details):
+        exc_type, exc_value, exc_tb = exc_details
+        exec("raise exc_type, exc_value, exc_tb")
+
+# Handle old-style classes if they exist
+try:
+    from types import InstanceType
+except ImportError:
+    # Python 3 doesn't have old-style classes
+    _get_type = type
+else:
+    # Need to handle old-style context managers on Python 2
+    def _get_type(obj):
+        obj_type = type(obj)
+        if obj_type is InstanceType:
+            return obj.__class__  # Old-style class
+        return obj_type  # New-style class
+
+
+# Inspired by discussions on http://bugs.python.org/issue13585
+class ExitStack(object):
+    """Context manager for dynamic management of a stack of exit callbacks
+
+    For example:
+
+        with ExitStack() as stack:
+            files = [stack.enter_context(open(fname)) for fname in filenames]
+            # All opened files will automatically be closed at the end of
+            # the with statement, even if attempts to open files later
+            # in the list raise an exception
+
+    """
+    def __init__(self):
+        self._exit_callbacks = deque()
+
+    def pop_all(self):
+        """Preserve the context stack by transferring it to a new instance"""
+        new_stack = type(self)()
+        new_stack._exit_callbacks = self._exit_callbacks
+        self._exit_callbacks = deque()
+        return new_stack
+
+    def _push_cm_exit(self, cm, cm_exit):
+        """Helper to correctly register callbacks to __exit__ methods"""
+        def _exit_wrapper(*exc_details):
+            return cm_exit(cm, *exc_details)
+        _exit_wrapper.__self__ = cm
+        self.push(_exit_wrapper)
+
+    def push(self, exit):
+        """Registers a callback with the standard __exit__ method signature
+
+        Can suppress exceptions the same way __exit__ methods can.
+
+        Also accepts any object with an __exit__ method (registering a call
+        to the method instead of the object itself)
+        """
+        # We use an unbound method rather than a bound method to follow
+        # the standard lookup behaviour for special methods
+        _cb_type = _get_type(exit)
+        try:
+            exit_method = _cb_type.__exit__
+        except AttributeError:
+            # Not a context manager, so assume its a callable
+            self._exit_callbacks.append(exit)
+        else:
+            self._push_cm_exit(exit, exit_method)
+        return exit # Allow use as a decorator
+
+    def callback(self, callback, *args, **kwds):
+        """Registers an arbitrary callback and arguments.
+
+        Cannot suppress exceptions.
+        """
+        def _exit_wrapper(exc_type, exc, tb):
+            callback(*args, **kwds)
+        # We changed the signature, so using @wraps is not appropriate, but
+        # setting __wrapped__ may still help with introspection
+        _exit_wrapper.__wrapped__ = callback
+        self.push(_exit_wrapper)
+        return callback # Allow use as a decorator
+
+    def enter_context(self, cm):
+        """Enters the supplied context manager
+
+        If successful, also pushes its __exit__ method as a callback and
+        returns the result of the __enter__ method.
+        """
+        # We look up the special methods on the type to match the with statement
+        _cm_type = _get_type(cm)
+        _exit = _cm_type.__exit__
+        result = _cm_type.__enter__(cm)
+        self._push_cm_exit(cm, _exit)
+        return result
+
+    def close(self):
+        """Immediately unwind the context stack"""
+        self.__exit__(None, None, None)
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, *exc_details):
+        received_exc = exc_details[0] is not None
+
+        # We manipulate the exception state so it behaves as though
+        # we were actually nesting multiple with statements
+        frame_exc = sys.exc_info()[1]
+        _fix_exception_context = _make_context_fixer(frame_exc)
+
+        # Callbacks are invoked in LIFO order to match the behaviour of
+        # nested context managers
+        suppressed_exc = False
+        pending_raise = False
+        while self._exit_callbacks:
+            cb = self._exit_callbacks.pop()
+            try:
+                if cb(*exc_details):
+                    suppressed_exc = True
+                    pending_raise = False
+                    exc_details = (None, None, None)
+            except:
+                new_exc_details = sys.exc_info()
+                # simulate the stack of exceptions by setting the context
+                _fix_exception_context(new_exc_details[1], exc_details[1])
+                pending_raise = True
+                exc_details = new_exc_details
+        if pending_raise:
+            _reraise_with_existing_context(exc_details)
+        return received_exc and suppressed_exc
+
+
+# Preserve backwards compatibility
+class ContextStack(ExitStack):
+    """Backwards compatibility alias for ExitStack"""
+
+    def __init__(self):
+        warnings.warn("ContextStack has been renamed to ExitStack",
+                      DeprecationWarning)
+        super(ContextStack, self).__init__()
+
+    def register_exit(self, callback):
+        return self.push(callback)
+
+    def register(self, callback, *args, **kwds):
+        return self.callback(callback, *args, **kwds)
+
+    def preserve(self):
+        return self.pop_all()
+
+
+class nullcontext(AbstractContextManager):
+    """Context manager that does no additional processing.
+    Used as a stand-in for a normal context manager, when a particular
+    block of code is only sometimes used with a normal context manager:
+    cm = optional_cm if condition else nullcontext()
+    with cm:
+        # Perform operation, using optional_cm if condition is True
+    """
+
+    def __init__(self, enter_result=None):
+        self.enter_result = enter_result
+
+    def __enter__(self):
+        return self.enter_result
+
+    def __exit__(self, *excinfo):
+        pass