1# #########################     LICENSE     ############################ #
2
3# Copyright (c) 2005-2017, Michele Simionato
4# All rights reserved.
5
6# Redistribution and use in source and binary forms, with or without
7# modification, are permitted provided that the following conditions are
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10#   Redistributions of source code must retain the above copyright
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12#   Redistributions in bytecode form must reproduce the above copyright
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14#   the documentation and/or other materials provided with the
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16
17# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
18# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
19# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
20# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
21# HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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26# TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
27# USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
28# DAMAGE.
29
30"""
31Decorator module, see http://pypi.python.org/pypi/decorator
32for the documentation.
33"""
34from __future__ import print_function
35
36import re
37import sys
38import inspect
39import operator
40import itertools
41import collections
42
43__version__ = '4.1.2'
44
45if sys.version >= '3':
46    from inspect import getfullargspec
47
48    def get_init(cls):
49        return cls.__init__
50else:
51    FullArgSpec = collections.namedtuple(
52        'FullArgSpec', 'args varargs varkw defaults '
53        'kwonlyargs kwonlydefaults')
54
55    def getfullargspec(f):
56        "A quick and dirty replacement for getfullargspec for Python 2.X"
57        return FullArgSpec._make(inspect.getargspec(f) + ([], None))
58
59    def get_init(cls):
60        return cls.__init__.__func__
61
62try:
63    iscoroutinefunction = inspect.iscoroutinefunction
64except AttributeError:
65    # let's assume there are no coroutine functions in old Python
66    def iscoroutinefunction(f):
67        return False
68
69# getargspec has been deprecated in Python 3.5
70ArgSpec = collections.namedtuple(
71    'ArgSpec', 'args varargs varkw defaults')
72
73
74def getargspec(f):
75    """A replacement for inspect.getargspec"""
76    spec = getfullargspec(f)
77    return ArgSpec(spec.args, spec.varargs, spec.varkw, spec.defaults)
78
79
80DEF = re.compile(r'\s*def\s*([_\w][_\w\d]*)\s*\(')
81
82
83# basic functionality
84class FunctionMaker(object):
85    """
86    An object with the ability to create functions with a given signature.
87    It has attributes name, doc, module, signature, defaults, dict and
88    methods update and make.
89    """
90
91    # Atomic get-and-increment provided by the GIL
92    _compile_count = itertools.count()
93
94    # make pylint happy
95    args = varargs = varkw = defaults = kwonlyargs = kwonlydefaults = ()
96
97    def __init__(self, func=None, name=None, signature=None,
98                 defaults=None, doc=None, module=None, funcdict=None):
99        self.shortsignature = signature
100        if func:
101            # func can be a class or a callable, but not an instance method
102            self.name = func.__name__
103            if self.name == '<lambda>':  # small hack for lambda functions
104                self.name = '_lambda_'
105            self.doc = func.__doc__
106            self.module = func.__module__
107            if inspect.isfunction(func):
108                argspec = getfullargspec(func)
109                self.annotations = getattr(func, '__annotations__', {})
110                for a in ('args', 'varargs', 'varkw', 'defaults', 'kwonlyargs',
111                          'kwonlydefaults'):
112                    setattr(self, a, getattr(argspec, a))
113                for i, arg in enumerate(self.args):
114                    setattr(self, 'arg%d' % i, arg)
115                if sys.version < '3':  # easy way
116                    self.shortsignature = self.signature = (
117                        inspect.formatargspec(
118                            formatvalue=lambda val: "", *argspec[:-2])[1:-1])
119                else:  # Python 3 way
120                    allargs = list(self.args)
121                    allshortargs = list(self.args)
122                    if self.varargs:
123                        allargs.append('*' + self.varargs)
124                        allshortargs.append('*' + self.varargs)
125                    elif self.kwonlyargs:
126                        allargs.append('*')  # single star syntax
127                    for a in self.kwonlyargs:
128                        allargs.append('%s=None' % a)
129                        allshortargs.append('%s=%s' % (a, a))
130                    if self.varkw:
131                        allargs.append('**' + self.varkw)
132                        allshortargs.append('**' + self.varkw)
133                    self.signature = ', '.join(allargs)
134                    self.shortsignature = ', '.join(allshortargs)
135                self.dict = func.__dict__.copy()
136        # func=None happens when decorating a caller
137        if name:
138            self.name = name
139        if signature is not None:
140            self.signature = signature
141        if defaults:
142            self.defaults = defaults
143        if doc:
144            self.doc = doc
145        if module:
146            self.module = module
147        if funcdict:
148            self.dict = funcdict
149        # check existence required attributes
150        assert hasattr(self, 'name')
151        if not hasattr(self, 'signature'):
152            raise TypeError('You are decorating a non function: %s' % func)
153
154    def update(self, func, **kw):
155        "Update the signature of func with the data in self"
156        func.__name__ = self.name
157        func.__doc__ = getattr(self, 'doc', None)
158        func.__dict__ = getattr(self, 'dict', {})
159        func.__defaults__ = self.defaults
160        func.__kwdefaults__ = self.kwonlydefaults or None
161        func.__annotations__ = getattr(self, 'annotations', None)
162        try:
163            frame = sys._getframe(3)
164        except AttributeError:  # for IronPython and similar implementations
165            callermodule = '?'
166        else:
167            callermodule = frame.f_globals.get('__name__', '?')
168        func.__module__ = getattr(self, 'module', callermodule)
169        func.__dict__.update(kw)
170
171    def make(self, src_templ, evaldict=None, addsource=False, **attrs):
172        "Make a new function from a given template and update the signature"
173        src = src_templ % vars(self)  # expand name and signature
174        evaldict = evaldict or {}
175        mo = DEF.search(src)
176        if mo is None:
177            raise SyntaxError('not a valid function template\n%s' % src)
178        name = mo.group(1)  # extract the function name
179        names = set([name] + [arg.strip(' *') for arg in
180                              self.shortsignature.split(',')])
181        for n in names:
182            if n in ('_func_', '_call_'):
183                raise NameError('%s is overridden in\n%s' % (n, src))
184
185        if not src.endswith('\n'):  # add a newline for old Pythons
186            src += '\n'
187
188        # Ensure each generated function has a unique filename for profilers
189        # (such as cProfile) that depend on the tuple of (<filename>,
190        # <definition line>, <function name>) being unique.
191        filename = '<decorator-gen-%d>' % (next(self._compile_count),)
192        try:
193            code = compile(src, filename, 'single')
194            exec(code, evaldict)
195        except:
196            print('Error in generated code:', file=sys.stderr)
197            print(src, file=sys.stderr)
198            raise
199        func = evaldict[name]
200        if addsource:
201            attrs['__source__'] = src
202        self.update(func, **attrs)
203        return func
204
205    @classmethod
206    def create(cls, obj, body, evaldict, defaults=None,
207               doc=None, module=None, addsource=True, **attrs):
208        """
209        Create a function from the strings name, signature and body.
210        evaldict is the evaluation dictionary. If addsource is true an
211        attribute __source__ is added to the result. The attributes attrs
212        are added, if any.
213        """
214        if isinstance(obj, str):  # "name(signature)"
215            name, rest = obj.strip().split('(', 1)
216            signature = rest[:-1]  # strip a right parens
217            func = None
218        else:  # a function
219            name = None
220            signature = None
221            func = obj
222        self = cls(func, name, signature, defaults, doc, module)
223        ibody = '\n'.join('    ' + line for line in body.splitlines())
224        caller = evaldict.get('_call_')  # when called from `decorate`
225        if caller and iscoroutinefunction(caller):
226            body = ('async def %(name)s(%(signature)s):\n' + ibody).replace(
227                'return', 'return await')
228        else:
229            body = 'def %(name)s(%(signature)s):\n' + ibody
230        return self.make(body, evaldict, addsource, **attrs)
231
232
233def decorate(func, caller):
234    """
235    decorate(func, caller) decorates a function using a caller.
236    """
237    evaldict = dict(_call_=caller, _func_=func)
238    fun = FunctionMaker.create(
239        func, "return _call_(_func_, %(shortsignature)s)",
240        evaldict, __wrapped__=func)
241    if hasattr(func, '__qualname__'):
242        fun.__qualname__ = func.__qualname__
243    return fun
244
245
246def decorator(caller, _func=None):
247    """decorator(caller) converts a caller function into a decorator"""
248    if _func is not None:  # return a decorated function
249        # this is obsolete behavior; you should use decorate instead
250        return decorate(_func, caller)
251    # else return a decorator function
252    if inspect.isclass(caller):
253        name = caller.__name__.lower()
254        doc = 'decorator(%s) converts functions/generators into ' \
255            'factories of %s objects' % (caller.__name__, caller.__name__)
256    elif inspect.isfunction(caller):
257        if caller.__name__ == '<lambda>':
258            name = '_lambda_'
259        else:
260            name = caller.__name__
261        doc = caller.__doc__
262    else:  # assume caller is an object with a __call__ method
263        name = caller.__class__.__name__.lower()
264        doc = caller.__call__.__doc__
265    evaldict = dict(_call=caller, _decorate_=decorate)
266    return FunctionMaker.create(
267        '%s(func)' % name, 'return _decorate_(func, _call)',
268        evaldict, doc=doc, module=caller.__module__,
269        __wrapped__=caller)
270
271
272# ####################### contextmanager ####################### #
273
274try:  # Python >= 3.2
275    from contextlib import _GeneratorContextManager
276except ImportError:  # Python >= 2.5
277    from contextlib import GeneratorContextManager as _GeneratorContextManager
278
279
280class ContextManager(_GeneratorContextManager):
281    def __call__(self, func):
282        """Context manager decorator"""
283        return FunctionMaker.create(
284            func, "with _self_: return _func_(%(shortsignature)s)",
285            dict(_self_=self, _func_=func), __wrapped__=func)
286
287
288init = getfullargspec(_GeneratorContextManager.__init__)
289n_args = len(init.args)
290if n_args == 2 and not init.varargs:  # (self, genobj) Python 2.7
291    def __init__(self, g, *a, **k):
292        return _GeneratorContextManager.__init__(self, g(*a, **k))
293    ContextManager.__init__ = __init__
294elif n_args == 2 and init.varargs:  # (self, gen, *a, **k) Python 3.4
295    pass
296elif n_args == 4:  # (self, gen, args, kwds) Python 3.5
297    def __init__(self, g, *a, **k):
298        return _GeneratorContextManager.__init__(self, g, a, k)
299    ContextManager.__init__ = __init__
300
301contextmanager = decorator(ContextManager)
302
303
304# ############################ dispatch_on ############################ #
305
306def append(a, vancestors):
307    """
308    Append ``a`` to the list of the virtual ancestors, unless it is already
309    included.
310    """
311    add = True
312    for j, va in enumerate(vancestors):
313        if issubclass(va, a):
314            add = False
315            break
316        if issubclass(a, va):
317            vancestors[j] = a
318            add = False
319    if add:
320        vancestors.append(a)
321
322
323# inspired from simplegeneric by P.J. Eby and functools.singledispatch
324def dispatch_on(*dispatch_args):
325    """
326    Factory of decorators turning a function into a generic function
327    dispatching on the given arguments.
328    """
329    assert dispatch_args, 'No dispatch args passed'
330    dispatch_str = '(%s,)' % ', '.join(dispatch_args)
331
332    def check(arguments, wrong=operator.ne, msg=''):
333        """Make sure one passes the expected number of arguments"""
334        if wrong(len(arguments), len(dispatch_args)):
335            raise TypeError('Expected %d arguments, got %d%s' %
336                            (len(dispatch_args), len(arguments), msg))
337
338    def gen_func_dec(func):
339        """Decorator turning a function into a generic function"""
340
341        # first check the dispatch arguments
342        argset = set(getfullargspec(func).args)
343        if not set(dispatch_args) <= argset:
344            raise NameError('Unknown dispatch arguments %s' % dispatch_str)
345
346        typemap = {}
347
348        def vancestors(*types):
349            """
350            Get a list of sets of virtual ancestors for the given types
351            """
352            check(types)
353            ras = [[] for _ in range(len(dispatch_args))]
354            for types_ in typemap:
355                for t, type_, ra in zip(types, types_, ras):
356                    if issubclass(t, type_) and type_ not in t.mro():
357                        append(type_, ra)
358            return [set(ra) for ra in ras]
359
360        def ancestors(*types):
361            """
362            Get a list of virtual MROs, one for each type
363            """
364            check(types)
365            lists = []
366            for t, vas in zip(types, vancestors(*types)):
367                n_vas = len(vas)
368                if n_vas > 1:
369                    raise RuntimeError(
370                        'Ambiguous dispatch for %s: %s' % (t, vas))
371                elif n_vas == 1:
372                    va, = vas
373                    mro = type('t', (t, va), {}).mro()[1:]
374                else:
375                    mro = t.mro()
376                lists.append(mro[:-1])  # discard t and object
377            return lists
378
379        def register(*types):
380            """
381            Decorator to register an implementation for the given types
382            """
383            check(types)
384
385            def dec(f):
386                check(getfullargspec(f).args, operator.lt, ' in ' + f.__name__)
387                typemap[types] = f
388                return f
389            return dec
390
391        def dispatch_info(*types):
392            """
393            An utility to introspect the dispatch algorithm
394            """
395            check(types)
396            lst = []
397            for anc in itertools.product(*ancestors(*types)):
398                lst.append(tuple(a.__name__ for a in anc))
399            return lst
400
401        def _dispatch(dispatch_args, *args, **kw):
402            types = tuple(type(arg) for arg in dispatch_args)
403            try:  # fast path
404                f = typemap[types]
405            except KeyError:
406                pass
407            else:
408                return f(*args, **kw)
409            combinations = itertools.product(*ancestors(*types))
410            next(combinations)  # the first one has been already tried
411            for types_ in combinations:
412                f = typemap.get(types_)
413                if f is not None:
414                    return f(*args, **kw)
415
416            # else call the default implementation
417            return func(*args, **kw)
418
419        return FunctionMaker.create(
420            func, 'return _f_(%s, %%(shortsignature)s)' % dispatch_str,
421            dict(_f_=_dispatch), register=register, default=func,
422            typemap=typemap, vancestors=vancestors, ancestors=ancestors,
423            dispatch_info=dispatch_info, __wrapped__=func)
424
425    gen_func_dec.__name__ = 'dispatch_on' + dispatch_str
426    return gen_func_dec
427