Add backports_abc 0.4 and singledispatch 3.4.0.3.

CHANGES.md

@@ -19,6 +19,8 @@
 * Update Requests library 2.7.0 (5d6d1bc) to 2.9.1 (a1c9b84)
 * Update SimpleJSON library 3.8.0 (a37a9bd) to 3.8.1 (6022794)
 * Update Six compatibility library 1.9.0 (r400) to 1.10.0 (r405)
+* Add backports_abc 0.4
+* Add singledispatch 3.4.0.3
 * Change refactor email notifier
 * Change emails to Unicode aware
 

lib/backports_abc.py

@@ -0,0 +1,202 @@
+"""
+Patch recently added ABCs into the standard lib module
+``collections.abc`` (Py3) or ``collections`` (Py2).
+
+Usage::
+
+    import backports_abc
+    backports_abc.patch()
+
+or::
+
+    try:
+        from collections.abc import Generator
+    except ImportError:
+        from backports_abc import Generator
+"""
+
+try:
+    import collections.abc as _collections_abc
+except ImportError:
+    import collections as _collections_abc
+
+
+def mk_gen():
+    from abc import abstractmethod
+
+    required_methods = (
+        '__iter__', '__next__' if hasattr(iter(()), '__next__') else 'next',
+         'send', 'throw', 'close')
+
+    class Generator(_collections_abc.Iterator):
+        __slots__ = ()
+
+        if '__next__' in required_methods:
+            def __next__(self):
+                return self.send(None)
+        else:
+            def next(self):
+                return self.send(None)
+
+        @abstractmethod
+        def send(self, value):
+            raise StopIteration
+
+        @abstractmethod
+        def throw(self, typ, val=None, tb=None):
+            if val is None:
+                if tb is None:
+                    raise typ
+                val = typ()
+            if tb is not None:
+                val = val.with_traceback(tb)
+            raise val
+
+        def close(self):
+            try:
+                self.throw(GeneratorExit)
+            except (GeneratorExit, StopIteration):
+                pass
+            else:
+                raise RuntimeError('generator ignored GeneratorExit')
+
+        @classmethod
+        def __subclasshook__(cls, C):
+            if cls is Generator:
+                mro = C.__mro__
+                for method in required_methods:
+                    for base in mro:
+                        if method in base.__dict__:
+                            break
+                    else:
+                        return NotImplemented
+                return True
+            return NotImplemented
+
+    generator = type((lambda: (yield))())
+    Generator.register(generator)
+    return Generator
+
+
+def mk_awaitable():
+    from abc import abstractmethod, ABCMeta
+
+    @abstractmethod
+    def __await__(self):
+        yield
+
+    @classmethod
+    def __subclasshook__(cls, C):
+        if cls is Awaitable:
+            for B in C.__mro__:
+                if '__await__' in B.__dict__:
+                    if B.__dict__['__await__']:
+                        return True
+                    break
+        return NotImplemented
+
+    # calling metaclass directly as syntax differs in Py2/Py3
+    Awaitable = ABCMeta('Awaitable', (), {
+        '__slots__': (),
+        '__await__': __await__,
+        '__subclasshook__': __subclasshook__,
+    })
+
+    return Awaitable
+
+
+def mk_coroutine():
+    from abc import abstractmethod
+
+    class Coroutine(Awaitable):
+        __slots__ = ()
+
+        @abstractmethod
+        def send(self, value):
+            """Send a value into the coroutine.
+            Return next yielded value or raise StopIteration.
+            """
+            raise StopIteration
+
+        @abstractmethod
+        def throw(self, typ, val=None, tb=None):
+            """Raise an exception in the coroutine.
+            Return next yielded value or raise StopIteration.
+            """
+            if val is None:
+                if tb is None:
+                    raise typ
+                val = typ()
+            if tb is not None:
+                val = val.with_traceback(tb)
+            raise val
+
+        def close(self):
+            """Raise GeneratorExit inside coroutine.
+            """
+            try:
+                self.throw(GeneratorExit)
+            except (GeneratorExit, StopIteration):
+                pass
+            else:
+                raise RuntimeError('coroutine ignored GeneratorExit')
+
+        @classmethod
+        def __subclasshook__(cls, C):
+            if cls is Coroutine:
+                mro = C.__mro__
+                for method in ('__await__', 'send', 'throw', 'close'):
+                    for base in mro:
+                        if method in base.__dict__:
+                            break
+                    else:
+                        return NotImplemented
+                return True
+            return NotImplemented
+
+    return Coroutine
+
+
+###
+#  make all ABCs available in this module
+
+try:
+    Generator = _collections_abc.Generator
+except AttributeError:
+    Generator = mk_gen()
+
+try:
+    Awaitable = _collections_abc.Awaitable
+except AttributeError:
+    Awaitable = mk_awaitable()
+
+try:
+    Coroutine = _collections_abc.Coroutine
+except AttributeError:
+    Coroutine = mk_coroutine()
+
+try:
+    from inspect import isawaitable
+except ImportError:
+    def isawaitable(obj):
+        return isinstance(obj, Awaitable)
+
+
+###
+#  allow patching the stdlib
+
+PATCHED = {}
+
+
+def patch(patch_inspect=True):
+    """
+    Main entry point for patching the ``collections.abc`` and ``inspect``
+    standard library modules.
+    """
+    PATCHED['collections.abc.Generator'] = _collections_abc.Generator = Generator
+    PATCHED['collections.abc.Coroutine'] = _collections_abc.Coroutine = Coroutine
+    PATCHED['collections.abc.Awaitable'] = _collections_abc.Awaitable = Awaitable
+
+    if patch_inspect:
+        import inspect
+        PATCHED['inspect.isawaitable'] = inspect.isawaitable = isawaitable

lib/singledispatch.py

@@ -0,0 +1,219 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+from __future__ import absolute_import
+from __future__ import division
+from __future__ import print_function
+from __future__ import unicode_literals
+
+__all__ = ['singledispatch']
+
+from functools import update_wrapper
+from weakref import WeakKeyDictionary
+from singledispatch_helpers import MappingProxyType, get_cache_token
+
+################################################################################
+### singledispatch() - single-dispatch generic function decorator
+################################################################################
+
+def _c3_merge(sequences):
+    """Merges MROs in *sequences* to a single MRO using the C3 algorithm.
+
+    Adapted from http://www.python.org/download/releases/2.3/mro/.
+
+    """
+    result = []
+    while True:
+        sequences = [s for s in sequences if s]   # purge empty sequences
+        if not sequences:
+            return result
+        for s1 in sequences:   # find merge candidates among seq heads
+            candidate = s1[0]
+            for s2 in sequences:
+                if candidate in s2[1:]:
+                    candidate = None
+                    break      # reject the current head, it appears later
+            else:
+                break
+        if not candidate:
+            raise RuntimeError("Inconsistent hierarchy")
+        result.append(candidate)
+        # remove the chosen candidate
+        for seq in sequences:
+            if seq[0] == candidate:
+                del seq[0]
+
+def _c3_mro(cls, abcs=None):
+    """Computes the method resolution order using extended C3 linearization.
+
+    If no *abcs* are given, the algorithm works exactly like the built-in C3
+    linearization used for method resolution.
+
+    If given, *abcs* is a list of abstract base classes that should be inserted
+    into the resulting MRO. Unrelated ABCs are ignored and don't end up in the
+    result. The algorithm inserts ABCs where their functionality is introduced,
+    i.e. issubclass(cls, abc) returns True for the class itself but returns
+    False for all its direct base classes. Implicit ABCs for a given class
+    (either registered or inferred from the presence of a special method like
+    __len__) are inserted directly after the last ABC explicitly listed in the
+    MRO of said class. If two implicit ABCs end up next to each other in the
+    resulting MRO, their ordering depends on the order of types in *abcs*.
+
+    """
+    for i, base in enumerate(reversed(cls.__bases__)):
+        if hasattr(base, '__abstractmethods__'):
+            boundary = len(cls.__bases__) - i
+            break   # Bases up to the last explicit ABC are considered first.
+    else:
+        boundary = 0
+    abcs = list(abcs) if abcs else []
+    explicit_bases = list(cls.__bases__[:boundary])
+    abstract_bases = []
+    other_bases = list(cls.__bases__[boundary:])
+    for base in abcs:
+        if issubclass(cls, base) and not any(
+                issubclass(b, base) for b in cls.__bases__
+            ):
+            # If *cls* is the class that introduces behaviour described by
+            # an ABC *base*, insert said ABC to its MRO.
+            abstract_bases.append(base)
+    for base in abstract_bases:
+        abcs.remove(base)
+    explicit_c3_mros = [_c3_mro(base, abcs=abcs) for base in explicit_bases]
+    abstract_c3_mros = [_c3_mro(base, abcs=abcs) for base in abstract_bases]
+    other_c3_mros = [_c3_mro(base, abcs=abcs) for base in other_bases]
+    return _c3_merge(
+        [[cls]] +
+        explicit_c3_mros + abstract_c3_mros + other_c3_mros +
+        [explicit_bases] + [abstract_bases] + [other_bases]
+    )
+
+def _compose_mro(cls, types):
+    """Calculates the method resolution order for a given class *cls*.
+
+    Includes relevant abstract base classes (with their respective bases) from
+    the *types* iterable. Uses a modified C3 linearization algorithm.
+
+    """
+    bases = set(cls.__mro__)
+    # Remove entries which are already present in the __mro__ or unrelated.
+    def is_related(typ):
+        return (typ not in bases and hasattr(typ, '__mro__')
+                                 and issubclass(cls, typ))
+    types = [n for n in types if is_related(n)]
+    # Remove entries which are strict bases of other entries (they will end up
+    # in the MRO anyway.
+    def is_strict_base(typ):
+        for other in types:
+            if typ != other and typ in other.__mro__:
+                return True
+        return False
+    types = [n for n in types if not is_strict_base(n)]
+    # Subclasses of the ABCs in *types* which are also implemented by
+    # *cls* can be used to stabilize ABC ordering.
+    type_set = set(types)
+    mro = []
+    for typ in types:
+        found = []
+        for sub in typ.__subclasses__():
+            if sub not in bases and issubclass(cls, sub):
+                found.append([s for s in sub.__mro__ if s in type_set])
+        if not found:
+            mro.append(typ)
+            continue
+        # Favor subclasses with the biggest number of useful bases
+        found.sort(key=len, reverse=True)
+        for sub in found:
+            for subcls in sub:
+                if subcls not in mro:
+                    mro.append(subcls)
+    return _c3_mro(cls, abcs=mro)
+
+def _find_impl(cls, registry):
+    """Returns the best matching implementation from *registry* for type *cls*.
+
+    Where there is no registered implementation for a specific type, its method
+    resolution order is used to find a more generic implementation.
+
+    Note: if *registry* does not contain an implementation for the base
+    *object* type, this function may return None.
+
+    """
+    mro = _compose_mro(cls, registry.keys())
+    match = None
+    for t in mro:
+        if match is not None:
+            # If *match* is an implicit ABC but there is another unrelated,
+            # equally matching implicit ABC, refuse the temptation to guess.
+            if (t in registry and t not in cls.__mro__
+                              and match not in cls.__mro__
+                              and not issubclass(match, t)):
+                raise RuntimeError("Ambiguous dispatch: {0} or {1}".format(
+                    match, t))
+            break
+        if t in registry:
+            match = t
+    return registry.get(match)
+
+def singledispatch(func):
+    """Single-dispatch generic function decorator.
+
+    Transforms a function into a generic function, which can have different
+    behaviours depending upon the type of its first argument. The decorated
+    function acts as the default implementation, and additional
+    implementations can be registered using the register() attribute of the
+    generic function.
+
+    """
+    registry = {}
+    dispatch_cache = WeakKeyDictionary()
+    def ns(): pass
+    ns.cache_token = None
+
+    def dispatch(cls):
+        """generic_func.dispatch(cls) -> <function implementation>
+
+        Runs the dispatch algorithm to return the best available implementation
+        for the given *cls* registered on *generic_func*.
+
+        """
+        if ns.cache_token is not None:
+            current_token = get_cache_token()
+            if ns.cache_token != current_token:
+                dispatch_cache.clear()
+                ns.cache_token = current_token
+        try:
+            impl = dispatch_cache[cls]
+        except KeyError:
+            try:
+                impl = registry[cls]
+            except KeyError:
+                impl = _find_impl(cls, registry)
+            dispatch_cache[cls] = impl
+        return impl
+
+    def register(cls, func=None):
+        """generic_func.register(cls, func) -> func
+
+        Registers a new implementation for the given *cls* on a *generic_func*.
+
+        """
+        if func is None:
+            return lambda f: register(cls, f)
+        registry[cls] = func
+        if ns.cache_token is None and hasattr(cls, '__abstractmethods__'):
+            ns.cache_token = get_cache_token()
+        dispatch_cache.clear()
+        return func
+
+    def wrapper(*args, **kw):
+        return dispatch(args[0].__class__)(*args, **kw)
+
+    registry[object] = func
+    wrapper.register = register
+    wrapper.dispatch = dispatch
+    wrapper.registry = MappingProxyType(registry)
+    wrapper._clear_cache = dispatch_cache.clear
+    update_wrapper(wrapper, func)
+    return wrapper
+

lib/singledispatch_helpers.py

@@ -0,0 +1,170 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+from __future__ import absolute_import
+from __future__ import division
+from __future__ import print_function
+from __future__ import unicode_literals
+
+from abc import ABCMeta
+from collections import MutableMapping
+import sys
+try:
+    from collections import UserDict
+except ImportError:
+    from UserDict import UserDict
+try:
+    from collections import OrderedDict
+except ImportError:
+    from ordereddict import OrderedDict
+try:
+    from thread import get_ident
+except ImportError:
+    try:
+        from _thread import get_ident
+    except ImportError:
+        from _dummy_thread import get_ident
+
+
+def recursive_repr(fillvalue='...'):
+    'Decorator to make a repr function return fillvalue for a recursive call'
+
+    def decorating_function(user_function):
+        repr_running = set()
+
+        def wrapper(self):
+            key = id(self), get_ident()
+            if key in repr_running:
+                return fillvalue
+            repr_running.add(key)
+            try:
+                result = user_function(self)
+            finally:
+                repr_running.discard(key)
+            return result
+
+        # Can't use functools.wraps() here because of bootstrap issues
+        wrapper.__module__ = getattr(user_function, '__module__')
+        wrapper.__doc__ = getattr(user_function, '__doc__')
+        wrapper.__name__ = getattr(user_function, '__name__')
+        wrapper.__annotations__ = getattr(user_function, '__annotations__', {})
+        return wrapper
+
+    return decorating_function
+
+
+class ChainMap(MutableMapping):
+    ''' A ChainMap groups multiple dicts (or other mappings) together
+    to create a single, updateable view.
+
+    The underlying mappings are stored in a list.  That list is public and can
+    accessed or updated using the *maps* attribute.  There is no other state.
+
+    Lookups search the underlying mappings successively until a key is found.
+    In contrast, writes, updates, and deletions only operate on the first
+    mapping.
+
+    '''
+
+    def __init__(self, *maps):
+        '''Initialize a ChainMap by setting *maps* to the given mappings.
+        If no mappings are provided, a single empty dictionary is used.
+
+        '''
+        self.maps = list(maps) or [{}]          # always at least one map
+
+    def __missing__(self, key):
+        raise KeyError(key)
+
+    def __getitem__(self, key):
+        for mapping in self.maps:
+            try:
+                return mapping[key]             # can't use 'key in mapping' with defaultdict
+            except KeyError:
+                pass
+        return self.__missing__(key)            # support subclasses that define __missing__
+
+    def get(self, key, default=None):
+        return self[key] if key in self else default
+
+    def __len__(self):
+        return len(set().union(*self.maps))     # reuses stored hash values if possible
+
+    def __iter__(self):
+        return iter(set().union(*self.maps))
+
+    def __contains__(self, key):
+        return any(key in m for m in self.maps)
+
+    @recursive_repr()
+    def __repr__(self):
+        return '{0.__class__.__name__}({1})'.format(
+            self, ', '.join(map(repr, self.maps)))
+
+    @classmethod
+    def fromkeys(cls, iterable, *args):
+        'Create a ChainMap with a single dict created from the iterable.'
+        return cls(dict.fromkeys(iterable, *args))
+
+    def copy(self):
+        'New ChainMap or subclass with a new copy of maps[0] and refs to maps[1:]'
+        return self.__class__(self.maps[0].copy(), *self.maps[1:])
+
+    __copy__ = copy
+
+    def new_child(self):                        # like Django's Context.push()
+        'New ChainMap with a new dict followed by all previous maps.'
+        return self.__class__({}, *self.maps)
+
+    @property
+    def parents(self):                          # like Django's Context.pop()
+        'New ChainMap from maps[1:].'
+        return self.__class__(*self.maps[1:])
+
+    def __setitem__(self, key, value):
+        self.maps[0][key] = value
+
+    def __delitem__(self, key):
+        try:
+            del self.maps[0][key]
+        except KeyError:
+            raise KeyError('Key not found in the first mapping: {!r}'.format(key))
+
+    def popitem(self):
+        'Remove and return an item pair from maps[0]. Raise KeyError is maps[0] is empty.'
+        try:
+            return self.maps[0].popitem()
+        except KeyError:
+            raise KeyError('No keys found in the first mapping.')
+
+    def pop(self, key, *args):
+        'Remove *key* from maps[0] and return its value. Raise KeyError if *key* not in maps[0].'
+        try:
+            return self.maps[0].pop(key, *args)
+        except KeyError:
+            raise KeyError('Key not found in the first mapping: {!r}'.format(key))
+
+    def clear(self):
+        'Clear maps[0], leaving maps[1:] intact.'
+        self.maps[0].clear()
+
+
+class MappingProxyType(UserDict):
+    def __init__(self, data):
+        UserDict.__init__(self)
+        self.data = data
+
+
+def get_cache_token():
+    return ABCMeta._abc_invalidation_counter
+
+
+
+class Support(object):
+    def dummy(self):
+        pass
+
+    def cpython_only(self, func):
+        if 'PyPy' in sys.version:
+            return self.dummy
+        return func