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# util/langhelpers.py
# Copyright (C) 2005-2021 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
"""Routines to help with the creation, loading and introspection of
modules, classes, hierarchies, attributes, functions, and methods.
"""
from functools import update_wrapper
import hashlib
import inspect
import itertools
import operator
import re
import sys
import textwrap
import types
import warnings
from . import _collections
from . import compat
from .. import exc
def md5_hex(x):
if compat.py3k:
x = x.encode("utf-8")
m = hashlib.md5()
m.update(x)
return m.hexdigest()
class safe_reraise(object):
"""Reraise an exception after invoking some
handler code.
Stores the existing exception info before
invoking so that it is maintained across a potential
coroutine context switch.
e.g.::
try:
sess.commit()
except:
with safe_reraise():
sess.rollback()
"""
__slots__ = ("warn_only", "_exc_info")
def __init__(self, warn_only=False):
self.warn_only = warn_only
def __enter__(self):
self._exc_info = sys.exc_info()
def __exit__(self, type_, value, traceback):
# see #2703 for notes
if type_ is None:
exc_type, exc_value, exc_tb = self._exc_info
self._exc_info = None # remove potential circular references
if not self.warn_only:
compat.raise_(
exc_value,
with_traceback=exc_tb,
)
else:
if not compat.py3k and self._exc_info and self._exc_info[1]:
# emulate Py3K's behavior of telling us when an exception
# occurs in an exception handler.
warn(
"An exception has occurred during handling of a "
"previous exception. The previous exception "
"is:\n %s %s\n" % (self._exc_info[0], self._exc_info[1])
)
self._exc_info = None # remove potential circular references
compat.raise_(value, with_traceback=traceback)
def clsname_as_plain_name(cls):
return " ".join(
n.lower() for n in re.findall(r"([A-Z][a-z]+)", cls.__name__)
)
def decode_slice(slc):
"""decode a slice object as sent to __getitem__.
takes into account the 2.5 __index__() method, basically.
"""
ret = []
for x in slc.start, slc.stop, slc.step:
if hasattr(x, "__index__"):
x = x.__index__()
ret.append(x)
return tuple(ret)
def _unique_symbols(used, *bases):
used = set(used)
for base in bases:
pool = itertools.chain(
(base,),
compat.itertools_imap(lambda i: base + str(i), range(1000)),
)
for sym in pool:
if sym not in used:
used.add(sym)
yield sym
break
else:
raise NameError("exhausted namespace for symbol base %s" % base)
def map_bits(fn, n):
"""Call the given function given each nonzero bit from n."""
while n:
b = n & (~n + 1)
yield fn(b)
n ^= b
def decorator(target):
"""A signature-matching decorator factory."""
def decorate(fn):
if not inspect.isfunction(fn) and not inspect.ismethod(fn):
raise Exception("not a decoratable function")
spec = compat.inspect_getfullargspec(fn)
names = tuple(spec[0]) + spec[1:3] + (fn.__name__,)
targ_name, fn_name = _unique_symbols(names, "target", "fn")
metadata = dict(target=targ_name, fn=fn_name)
metadata.update(format_argspec_plus(spec, grouped=False))
metadata["name"] = fn.__name__
code = (
"""\
def %(name)s(%(args)s):
return %(target)s(%(fn)s, %(apply_kw)s)
"""
% metadata
)
decorated = _exec_code_in_env(
code, {targ_name: target, fn_name: fn}, fn.__name__
)
decorated.__defaults__ = getattr(fn, "im_func", fn).__defaults__
decorated.__wrapped__ = fn
return update_wrapper(decorated, fn)
return update_wrapper(decorate, target)
def _exec_code_in_env(code, env, fn_name):
exec(code, env)
return env[fn_name]
def public_factory(target, location, class_location=None):
"""Produce a wrapping function for the given cls or classmethod.
Rationale here is so that the __init__ method of the
class can serve as documentation for the function.
"""
if isinstance(target, type):
fn = target.__init__
callable_ = target
doc = (
"Construct a new :class:`%s` object. \n\n"
"This constructor is mirrored as a public API function; "
"see :func:`sqlalchemy%s` "
"for a full usage and argument description."
% (
class_location if class_location else ".%s" % target.__name__,
location,
)
)
else:
fn = callable_ = target
doc = (
"This function is mirrored; see :func:`sqlalchemy%s` "
"for a description of arguments." % location
)
location_name = location.split(".")[-1]
spec = compat.inspect_getfullargspec(fn)
del spec[0][0]
metadata = format_argspec_plus(spec, grouped=False)
metadata["name"] = location_name
code = (
"""\
def %(name)s(%(args)s):
return cls(%(apply_kw)s)
"""
% metadata
)
env = {"cls": callable_, "symbol": symbol}
exec(code, env)
decorated = env[location_name]
if hasattr(fn, "_linked_to"):
linked_to, linked_to_location = fn._linked_to
linked_to_doc = linked_to.__doc__
if class_location is None:
class_location = "%s.%s" % (target.__module__, target.__name__)
linked_to_doc = inject_docstring_text(
linked_to_doc,
".. container:: inherited_member\n\n "
"This documentation is inherited from :func:`sqlalchemy%s`; "
"this constructor, :func:`sqlalchemy%s`, "
"creates a :class:`sqlalchemy%s` object. See that class for "
"additional details describing this subclass."
% (linked_to_location, location, class_location),
1,
)
decorated.__doc__ = linked_to_doc
else:
decorated.__doc__ = fn.__doc__
decorated.__module__ = "sqlalchemy" + location.rsplit(".", 1)[0]
if decorated.__module__ not in sys.modules:
raise ImportError(
"public_factory location %s is not in sys.modules"
% (decorated.__module__,)
)
if compat.py2k or hasattr(fn, "__func__"):
fn.__func__.__doc__ = doc
if not hasattr(fn.__func__, "_linked_to"):
fn.__func__._linked_to = (decorated, location)
else:
fn.__doc__ = doc
if not hasattr(fn, "_linked_to"):
fn._linked_to = (decorated, location)
return decorated
class PluginLoader(object):
def __init__(self, group, auto_fn=None):
self.group = group
self.impls = {}
self.auto_fn = auto_fn
def clear(self):
self.impls.clear()
def load(self, name):
if name in self.impls:
return self.impls[name]()
if self.auto_fn:
loader = self.auto_fn(name)
if loader:
self.impls[name] = loader
return loader()
try:
import pkg_resources
except ImportError:
pass
else:
for impl in pkg_resources.iter_entry_points(self.group, name):
self.impls[name] = impl.load
return impl.load()
raise exc.NoSuchModuleError(
"Can't load plugin: %s:%s" % (self.group, name)
)
def register(self, name, modulepath, objname):
def load():
mod = compat.import_(modulepath)
for token in modulepath.split(".")[1:]:
mod = getattr(mod, token)
return getattr(mod, objname)
self.impls[name] = load
def _inspect_func_args(fn):
try:
co_varkeywords = inspect.CO_VARKEYWORDS
except AttributeError:
# https://docs.python.org/3/library/inspect.html
# The flags are specific to CPython, and may not be defined in other
# Python implementations. Furthermore, the flags are an implementation
# detail, and can be removed or deprecated in future Python releases.
spec = compat.inspect_getfullargspec(fn)
return spec[0], bool(spec[2])
else:
# use fn.__code__ plus flags to reduce method call overhead
co = fn.__code__
nargs = co.co_argcount
return (
list(co.co_varnames[:nargs]),
bool(co.co_flags & co_varkeywords),
)
def get_cls_kwargs(cls, _set=None):
r"""Return the full set of inherited kwargs for the given `cls`.
Probes a class's __init__ method, collecting all named arguments. If the
__init__ defines a \**kwargs catch-all, then the constructor is presumed
to pass along unrecognized keywords to its base classes, and the
collection process is repeated recursively on each of the bases.
Uses a subset of inspect.getfullargspec() to cut down on method overhead,
as this is used within the Core typing system to create copies of type
objects which is a performance-sensitive operation.
No anonymous tuple arguments please !
"""
toplevel = _set is None
if toplevel:
_set = set()
ctr = cls.__dict__.get("__init__", False)
has_init = (
ctr
and isinstance(ctr, types.FunctionType)
and isinstance(ctr.__code__, types.CodeType)
)
if has_init:
names, has_kw = _inspect_func_args(ctr)
_set.update(names)
if not has_kw and not toplevel:
return None
if not has_init or has_kw:
for c in cls.__bases__:
if get_cls_kwargs(c, _set) is None:
break
_set.discard("self")
return _set
def get_func_kwargs(func):
"""Return the set of legal kwargs for the given `func`.
Uses getargspec so is safe to call for methods, functions,
etc.
"""
return compat.inspect_getfullargspec(func)[0]
def get_callable_argspec(fn, no_self=False, _is_init=False):
"""Return the argument signature for any callable.
All pure-Python callables are accepted, including
functions, methods, classes, objects with __call__;
builtins and other edge cases like functools.partial() objects
raise a TypeError.
"""
if inspect.isbuiltin(fn):
raise TypeError("Can't inspect builtin: %s" % fn)
elif inspect.isfunction(fn):
if _is_init and no_self:
spec = compat.inspect_getfullargspec(fn)
return compat.FullArgSpec(
spec.args[1:],
spec.varargs,
spec.varkw,
spec.defaults,
spec.kwonlyargs,
spec.kwonlydefaults,
spec.annotations,
)
else:
return compat.inspect_getfullargspec(fn)
elif inspect.ismethod(fn):
if no_self and (_is_init or fn.__self__):
spec = compat.inspect_getfullargspec(fn.__func__)
return compat.FullArgSpec(
spec.args[1:],
spec.varargs,
spec.varkw,
spec.defaults,
spec.kwonlyargs,
spec.kwonlydefaults,
spec.annotations,
)
else:
return compat.inspect_getfullargspec(fn.__func__)
elif inspect.isclass(fn):
return get_callable_argspec(
fn.__init__, no_self=no_self, _is_init=True
)
elif hasattr(fn, "__func__"):
return compat.inspect_getfullargspec(fn.__func__)
elif hasattr(fn, "__call__"):
if inspect.ismethod(fn.__call__):
return get_callable_argspec(fn.__call__, no_self=no_self)
else:
raise TypeError("Can't inspect callable: %s" % fn)
else:
raise TypeError("Can't inspect callable: %s" % fn)
def format_argspec_plus(fn, grouped=True):
"""Returns a dictionary of formatted, introspected function arguments.
A enhanced variant of inspect.formatargspec to support code generation.
fn
An inspectable callable or tuple of inspect getargspec() results.
grouped
Defaults to True; include (parens, around, argument) lists
Returns:
args
Full inspect.formatargspec for fn
self_arg
The name of the first positional argument, varargs[0], or None
if the function defines no positional arguments.
apply_pos
args, re-written in calling rather than receiving syntax. Arguments are
passed positionally.
apply_kw
Like apply_pos, except keyword-ish args are passed as keywords.
Example::
>>> format_argspec_plus(lambda self, a, b, c=3, **d: 123)
{'args': '(self, a, b, c=3, **d)',
'self_arg': 'self',
'apply_kw': '(self, a, b, c=c, **d)',
'apply_pos': '(self, a, b, c, **d)'}
"""
if compat.callable(fn):
spec = compat.inspect_getfullargspec(fn)
else:
spec = fn
args = compat.inspect_formatargspec(*spec)
if spec[0]:
self_arg = spec[0][0]
elif spec[1]:
self_arg = "%s[0]" % spec[1]
else:
self_arg = None
apply_pos = compat.inspect_formatargspec(
spec[0], spec[1], spec[2], None, spec[4]
)
num_defaults = 0
if spec[3]:
num_defaults += len(spec[3])
if spec[4]:
num_defaults += len(spec[4])
name_args = spec[0] + spec[4]
if num_defaults:
defaulted_vals = name_args[0 - num_defaults :]
else:
defaulted_vals = ()
apply_kw = compat.inspect_formatargspec(
name_args,
spec[1],
spec[2],
defaulted_vals,
formatvalue=lambda x: "=" + x,
)
if grouped:
return dict(
args=args,
self_arg=self_arg,
apply_pos=apply_pos,
apply_kw=apply_kw,
)
else:
return dict(
args=args[1:-1],
self_arg=self_arg,
apply_pos=apply_pos[1:-1],
apply_kw=apply_kw[1:-1],
)
def format_argspec_init(method, grouped=True):
"""format_argspec_plus with considerations for typical __init__ methods
Wraps format_argspec_plus with error handling strategies for typical
__init__ cases::
object.__init__ -> (self)
other unreflectable (usually C) -> (self, *args, **kwargs)
"""
if method is object.__init__:
args = grouped and "(self)" or "self"
else:
try:
return format_argspec_plus(method, grouped=grouped)
except TypeError:
args = (
grouped
and "(self, *args, **kwargs)"
or "self, *args, **kwargs"
)
return dict(self_arg="self", args=args, apply_pos=args, apply_kw=args)
def getargspec_init(method):
"""inspect.getargspec with considerations for typical __init__ methods
Wraps inspect.getargspec with error handling for typical __init__ cases::
object.__init__ -> (self)
other unreflectable (usually C) -> (self, *args, **kwargs)
"""
try:
return compat.inspect_getfullargspec(method)
except TypeError:
if method is object.__init__:
return (["self"], None, None, None)
else:
return (["self"], "args", "kwargs", None)
def unbound_method_to_callable(func_or_cls):
"""Adjust the incoming callable such that a 'self' argument is not
required.
"""
if isinstance(func_or_cls, types.MethodType) and not func_or_cls.__self__:
return func_or_cls.__func__
else:
return func_or_cls
def generic_repr(obj, additional_kw=(), to_inspect=None, omit_kwarg=()):
"""Produce a __repr__() based on direct association of the __init__()
specification vs. same-named attributes present.
"""
if to_inspect is None:
to_inspect = [obj]
else:
to_inspect = _collections.to_list(to_inspect)
missing = object()
pos_args = []
kw_args = _collections.OrderedDict()
vargs = None
for i, insp in enumerate(to_inspect):
try:
spec = compat.inspect_getfullargspec(insp.__init__)
except TypeError:
continue
else:
default_len = spec.defaults and len(spec.defaults) or 0
if i == 0:
if spec.varargs:
vargs = spec.varargs
if default_len:
pos_args.extend(spec.args[1:-default_len])
else:
pos_args.extend(spec.args[1:])
else:
kw_args.update(
[(arg, missing) for arg in spec.args[1:-default_len]]
)
if default_len:
kw_args.update(
[
(arg, default)
for arg, default in zip(
spec.args[-default_len:], spec.defaults
)
]
)
output = []
output.extend(repr(getattr(obj, arg, None)) for arg in pos_args)
if vargs is not None and hasattr(obj, vargs):
output.extend([repr(val) for val in getattr(obj, vargs)])
for arg, defval in kw_args.items():
if arg in omit_kwarg:
continue
try:
val = getattr(obj, arg, missing)
if val is not missing and val != defval:
output.append("%s=%r" % (arg, val))
except Exception:
pass
if additional_kw:
for arg, defval in additional_kw:
try:
val = getattr(obj, arg, missing)
if val is not missing and val != defval:
output.append("%s=%r" % (arg, val))
except Exception:
pass
return "%s(%s)" % (obj.__class__.__name__, ", ".join(output))
class portable_instancemethod(object):
"""Turn an instancemethod into a (parent, name) pair
to produce a serializable callable.
"""
__slots__ = "target", "name", "kwargs", "__weakref__"
def __getstate__(self):
return {
"target": self.target,
"name": self.name,
"kwargs": self.kwargs,
}
def __setstate__(self, state):
self.target = state["target"]
self.name = state["name"]
self.kwargs = state.get("kwargs", ())
def __init__(self, meth, kwargs=()):
self.target = meth.__self__
self.name = meth.__name__
self.kwargs = kwargs
def __call__(self, *arg, **kw):
kw.update(self.kwargs)
return getattr(self.target, self.name)(*arg, **kw)
def class_hierarchy(cls):
"""Return an unordered sequence of all classes related to cls.
Traverses diamond hierarchies.
Fibs slightly: subclasses of builtin types are not returned. Thus
class_hierarchy(class A(object)) returns (A, object), not A plus every
class systemwide that derives from object.
Old-style classes are discarded and hierarchies rooted on them
will not be descended.
"""
if compat.py2k:
if isinstance(cls, types.ClassType):
return list()
hier = {cls}
process = list(cls.__mro__)
while process:
c = process.pop()
if compat.py2k:
if isinstance(c, types.ClassType):
continue
bases = (
_
for _ in c.__bases__
if _ not in hier and not isinstance(_, types.ClassType)
)
else:
bases = (_ for _ in c.__bases__ if _ not in hier)
for b in bases:
process.append(b)
hier.add(b)
if compat.py3k:
if c.__module__ == "builtins" or not hasattr(c, "__subclasses__"):
continue
else:
if c.__module__ == "__builtin__" or not hasattr(
c, "__subclasses__"
):
continue
for s in [_ for _ in c.__subclasses__() if _ not in hier]:
process.append(s)
hier.add(s)
return list(hier)
def iterate_attributes(cls):
"""iterate all the keys and attributes associated
with a class, without using getattr().
Does not use getattr() so that class-sensitive
descriptors (i.e. property.__get__()) are not called.
"""
keys = dir(cls)
for key in keys:
for c in cls.__mro__:
if key in c.__dict__:
yield (key, c.__dict__[key])
break
def monkeypatch_proxied_specials(
into_cls,
from_cls,
skip=None,
only=None,
name="self.proxy",
from_instance=None,
):
"""Automates delegation of __specials__ for a proxying type."""
if only:
dunders = only
else:
if skip is None:
skip = (
"__slots__",
"__del__",
"__getattribute__",
"__metaclass__",
"__getstate__",
"__setstate__",
)
dunders = [
m
for m in dir(from_cls)
if (
m.startswith("__")
and m.endswith("__")
and not hasattr(into_cls, m)
and m not in skip
)
]
for method in dunders:
try:
fn = getattr(from_cls, method)
if not hasattr(fn, "__call__"):
continue
fn = getattr(fn, "im_func", fn)
except AttributeError:
continue
try:
spec = compat.inspect_getfullargspec(fn)
fn_args = compat.inspect_formatargspec(spec[0])
d_args = compat.inspect_formatargspec(spec[0][1:])
except TypeError:
fn_args = "(self, *args, **kw)"
d_args = "(*args, **kw)"
py = (
"def %(method)s%(fn_args)s: "
"return %(name)s.%(method)s%(d_args)s" % locals()
)
env = from_instance is not None and {name: from_instance} or {}
compat.exec_(py, env)
try:
env[method].__defaults__ = fn.__defaults__
except AttributeError:
pass
setattr(into_cls, method, env[method])
def methods_equivalent(meth1, meth2):
"""Return True if the two methods are the same implementation."""
return getattr(meth1, "__func__", meth1) is getattr(
meth2, "__func__", meth2
)
def as_interface(obj, cls=None, methods=None, required=None):
"""Ensure basic interface compliance for an instance or dict of callables.
Checks that ``obj`` implements public methods of ``cls`` or has members
listed in ``methods``. If ``required`` is not supplied, implementing at
least one interface method is sufficient. Methods present on ``obj`` that
are not in the interface are ignored.
If ``obj`` is a dict and ``dict`` does not meet the interface
requirements, the keys of the dictionary are inspected. Keys present in
``obj`` that are not in the interface will raise TypeErrors.
Raises TypeError if ``obj`` does not meet the interface criteria.
In all passing cases, an object with callable members is returned. In the
simple case, ``obj`` is returned as-is; if dict processing kicks in then
an anonymous class is returned.
obj
A type, instance, or dictionary of callables.
cls
Optional, a type. All public methods of cls are considered the
interface. An ``obj`` instance of cls will always pass, ignoring
``required``..
methods
Optional, a sequence of method names to consider as the interface.
required
Optional, a sequence of mandatory implementations. If omitted, an
``obj`` that provides at least one interface method is considered
sufficient. As a convenience, required may be a type, in which case
all public methods of the type are required.
"""
if not cls and not methods:
raise TypeError("a class or collection of method names are required")
if isinstance(cls, type) and isinstance(obj, cls):
return obj
interface = set(methods or [m for m in dir(cls) if not m.startswith("_")])
implemented = set(dir(obj))
complies = operator.ge
if isinstance(required, type):
required = interface
elif not required:
required = set()
complies = operator.gt
else:
required = set(required)
if complies(implemented.intersection(interface), required):
return obj
# No dict duck typing here.
if not isinstance(obj, dict):
qualifier = complies is operator.gt and "any of" or "all of"
raise TypeError(
"%r does not implement %s: %s"
% (obj, qualifier, ", ".join(interface))
)
class AnonymousInterface(object):
"""A callable-holding shell."""
if cls:
AnonymousInterface.__name__ = "Anonymous" + cls.__name__
found = set()
for method, impl in dictlike_iteritems(obj):
if method not in interface:
raise TypeError("%r: unknown in this interface" % method)
if not compat.callable(impl):
raise TypeError("%r=%r is not callable" % (method, impl))
setattr(AnonymousInterface, method, staticmethod(impl))
found.add(method)
if complies(found, required):
return AnonymousInterface
raise TypeError(
"dictionary does not contain required keys %s"
% ", ".join(required - found)
)
class memoized_property(object):
"""A read-only @property that is only evaluated once."""
def __init__(self, fget, doc=None):
self.fget = fget
self.__doc__ = doc or fget.__doc__
self.__name__ = fget.__name__
def __get__(self, obj, cls):
if obj is None:
return self
obj.__dict__[self.__name__] = result = self.fget(obj)
return result
def _reset(self, obj):
memoized_property.reset(obj, self.__name__)
@classmethod
def reset(cls, obj, name):
obj.__dict__.pop(name, None)
def memoized_instancemethod(fn):
"""Decorate a method memoize its return value.
Best applied to no-arg methods: memoization is not sensitive to
argument values, and will always return the same value even when
called with different arguments.
"""
def oneshot(self, *args, **kw):
result = fn(self, *args, **kw)
def memo(*a, **kw):
return result
memo.__name__ = fn.__name__
memo.__doc__ = fn.__doc__
self.__dict__[fn.__name__] = memo
return result
return update_wrapper(oneshot, fn)
class group_expirable_memoized_property(object):
"""A family of @memoized_properties that can be expired in tandem."""
def __init__(self, attributes=()):
self.attributes = []
if attributes:
self.attributes.extend(attributes)
def expire_instance(self, instance):
"""Expire all memoized properties for *instance*."""
stash = instance.__dict__
for attribute in self.attributes:
stash.pop(attribute, None)
def __call__(self, fn):
self.attributes.append(fn.__name__)
return memoized_property(fn)
def method(self, fn):
self.attributes.append(fn.__name__)
return memoized_instancemethod(fn)
class MemoizedSlots(object):
"""Apply memoized items to an object using a __getattr__ scheme.
This allows the functionality of memoized_property and
memoized_instancemethod to be available to a class using __slots__.
"""
__slots__ = ()
def _fallback_getattr(self, key):
raise AttributeError(key)
def __getattr__(self, key):
if key.startswith("_memoized"):
raise AttributeError(key)
elif hasattr(self, "_memoized_attr_%s" % key):
value = getattr(self, "_memoized_attr_%s" % key)()
setattr(self, key, value)
return value
elif hasattr(self, "_memoized_method_%s" % key):
fn = getattr(self, "_memoized_method_%s" % key)
def oneshot(*args, **kw):
result = fn(*args, **kw)
def memo(*a, **kw):
return result
memo.__name__ = fn.__name__
memo.__doc__ = fn.__doc__
setattr(self, key, memo)
return result
oneshot.__doc__ = fn.__doc__
return oneshot
else:
return self._fallback_getattr(key)
def dependency_for(modulename, add_to_all=False):
def decorate(obj):
tokens = modulename.split(".")
mod = compat.import_(
".".join(tokens[0:-1]), globals(), locals(), [tokens[-1]]
)
mod = getattr(mod, tokens[-1])
setattr(mod, obj.__name__, obj)
if add_to_all and hasattr(mod, "__all__"):
mod.__all__.append(obj.__name__)
return obj
return decorate
def asbool(obj):
if isinstance(obj, compat.string_types):
obj = obj.strip().lower()
if obj in ["true", "yes", "on", "y", "t", "1"]:
return True
elif obj in ["false", "no", "off", "n", "f", "0"]:
return False
else:
raise ValueError("String is not true/false: %r" % obj)
return bool(obj)
def bool_or_str(*text):
"""Return a callable that will evaluate a string as
boolean, or one of a set of "alternate" string values.
"""
def bool_or_value(obj):
if obj in text:
return obj
else:
return asbool(obj)
return bool_or_value
def asint(value):
"""Coerce to integer."""
if value is None:
return value
return int(value)
def coerce_kw_type(kw, key, type_, flexi_bool=True, dest=None):
r"""If 'key' is present in dict 'kw', coerce its value to type 'type\_' if
necessary. If 'flexi_bool' is True, the string '0' is considered false
when coercing to boolean.
"""
if dest is None:
dest = kw
if (
key in kw
and (not isinstance(type_, type) or not isinstance(kw[key], type_))
and kw[key] is not None
):
if type_ is bool and flexi_bool:
dest[key] = asbool(kw[key])
else:
dest[key] = type_(kw[key])
def constructor_copy(obj, cls, *args, **kw):
"""Instantiate cls using the __dict__ of obj as constructor arguments.
Uses inspect to match the named arguments of ``cls``.
"""
names = get_cls_kwargs(cls)
kw.update(
(k, obj.__dict__[k]) for k in names.difference(kw) if k in obj.__dict__
)
return cls(*args, **kw)
def counter():
"""Return a threadsafe counter function."""
lock = compat.threading.Lock()
counter = itertools.count(1)
# avoid the 2to3 "next" transformation...
def _next():
lock.acquire()
try:
return next(counter)
finally:
lock.release()
return _next
def duck_type_collection(specimen, default=None):
"""Given an instance or class, guess if it is or is acting as one of
the basic collection types: list, set and dict. If the __emulates__
property is present, return that preferentially.
"""
if hasattr(specimen, "__emulates__"):
# canonicalize set vs sets.Set to a standard: the builtin set
if specimen.__emulates__ is not None and issubclass(
specimen.__emulates__, set
):
return set
else:
return specimen.__emulates__
isa = isinstance(specimen, type) and issubclass or isinstance
if isa(specimen, list):
return list
elif isa(specimen, set):
return set
elif isa(specimen, dict):
return dict
if hasattr(specimen, "append"):
return list
elif hasattr(specimen, "add"):
return set
elif hasattr(specimen, "set"):
return dict
else:
return default
def assert_arg_type(arg, argtype, name):
if isinstance(arg, argtype):
return arg
else:
if isinstance(argtype, tuple):
raise exc.ArgumentError(
"Argument '%s' is expected to be one of type %s, got '%s'"
% (name, " or ".join("'%s'" % a for a in argtype), type(arg))
)
else:
raise exc.ArgumentError(
"Argument '%s' is expected to be of type '%s', got '%s'"
% (name, argtype, type(arg))
)
def dictlike_iteritems(dictlike):
"""Return a (key, value) iterator for almost any dict-like object."""
if compat.py3k:
if hasattr(dictlike, "items"):
return list(dictlike.items())
else:
if hasattr(dictlike, "iteritems"):
return dictlike.iteritems()
elif hasattr(dictlike, "items"):
return iter(dictlike.items())
getter = getattr(dictlike, "__getitem__", getattr(dictlike, "get", None))
if getter is None:
raise TypeError("Object '%r' is not dict-like" % dictlike)
if hasattr(dictlike, "iterkeys"):
def iterator():
for key in dictlike.iterkeys():
yield key, getter(key)
return iterator()
elif hasattr(dictlike, "keys"):
return iter((key, getter(key)) for key in dictlike.keys())
else:
raise TypeError("Object '%r' is not dict-like" % dictlike)
class classproperty(property):
"""A decorator that behaves like @property except that operates
on classes rather than instances.
The decorator is currently special when using the declarative
module, but note that the
:class:`~.sqlalchemy.ext.declarative.declared_attr`
decorator should be used for this purpose with declarative.
"""
def __init__(self, fget, *arg, **kw):
super(classproperty, self).__init__(fget, *arg, **kw)
self.__doc__ = fget.__doc__
def __get__(desc, self, cls):
return desc.fget(cls)
class hybridproperty(object):
def __init__(self, func):
self.func = func
def __get__(self, instance, owner):
if instance is None:
clsval = self.func(owner)
clsval.__doc__ = self.func.__doc__
return clsval
else:
return self.func(instance)
class hybridmethod(object):
"""Decorate a function as cls- or instance- level."""
def __init__(self, func):
self.func = func
def __get__(self, instance, owner):
if instance is None:
return self.func.__get__(owner, owner.__class__)
else:
return self.func.__get__(instance, owner)
class _symbol(int):
def __new__(self, name, doc=None, canonical=None):
"""Construct a new named symbol."""
assert isinstance(name, compat.string_types)
if canonical is None:
canonical = hash(name)
v = int.__new__(_symbol, canonical)
v.name = name
if doc:
v.__doc__ = doc
return v
def __reduce__(self):
return symbol, (self.name, "x", int(self))
def __str__(self):
return repr(self)
def __repr__(self):
return "symbol(%r)" % self.name
_symbol.__name__ = "symbol"
class symbol(object):
"""A constant symbol.
>>> symbol('foo') is symbol('foo')
True
>>> symbol('foo')
<symbol 'foo>
A slight refinement of the MAGICCOOKIE=object() pattern. The primary
advantage of symbol() is its repr(). They are also singletons.
Repeated calls of symbol('name') will all return the same instance.
The optional ``doc`` argument assigns to ``__doc__``. This
is strictly so that Sphinx autoattr picks up the docstring we want
(it doesn't appear to pick up the in-module docstring if the datamember
is in a different module - autoattribute also blows up completely).
If Sphinx fixes/improves this then we would no longer need
``doc`` here.
"""
symbols = {}
_lock = compat.threading.Lock()
def __new__(cls, name, doc=None, canonical=None):
cls._lock.acquire()
try:
sym = cls.symbols.get(name)
if sym is None:
cls.symbols[name] = sym = _symbol(name, doc, canonical)
return sym
finally:
symbol._lock.release()
@classmethod
def parse_user_argument(
cls, arg, choices, name, resolve_symbol_names=False
):
"""Given a user parameter, parse the parameter into a chosen symbol.
The user argument can be a string name that matches the name of a
symbol, or the symbol object itself, or any number of alternate choices
such as True/False/ None etc.
:param arg: the user argument.
:param choices: dictionary of symbol object to list of possible
entries.
:param name: name of the argument. Used in an :class:`.ArgumentError`
that is raised if the parameter doesn't match any available argument.
:param resolve_symbol_names: include the name of each symbol as a valid
entry.
"""
# note using hash lookup is tricky here because symbol's `__hash__`
# is its int value which we don't want included in the lookup
# explicitly, so we iterate and compare each.
for sym, choice in choices.items():
if arg is sym:
return sym
elif resolve_symbol_names and arg == sym.name:
return sym
elif arg in choice:
return sym
if arg is None:
return None
raise exc.ArgumentError("Invalid value for '%s': %r" % (name, arg))
_creation_order = 1
def set_creation_order(instance):
"""Assign a '_creation_order' sequence to the given instance.
This allows multiple instances to be sorted in order of creation
(typically within a single thread; the counter is not particularly
threadsafe).
"""
global _creation_order
instance._creation_order = _creation_order
_creation_order += 1
def warn_exception(func, *args, **kwargs):
"""executes the given function, catches all exceptions and converts to
a warning.
"""
try:
return func(*args, **kwargs)
except Exception:
warn("%s('%s') ignored" % sys.exc_info()[0:2])
def ellipses_string(value, len_=25):
try:
if len(value) > len_:
return "%s..." % value[0:len_]
else:
return value
except TypeError:
return value
class _hash_limit_string(compat.text_type):
"""A string subclass that can only be hashed on a maximum amount
of unique values.
This is used for warnings so that we can send out parameterized warnings
without the __warningregistry__ of the module, or the non-overridable
"once" registry within warnings.py, overloading memory,
"""
def __new__(cls, value, num, args):
interpolated = (value % args) + (
" (this warning may be suppressed after %d occurrences)" % num
)
self = super(_hash_limit_string, cls).__new__(cls, interpolated)
self._hash = hash("%s_%d" % (value, hash(interpolated) % num))
return self
def __hash__(self):
return self._hash
def __eq__(self, other):
return hash(self) == hash(other)
def warn(msg):
"""Issue a warning.
If msg is a string, :class:`.exc.SAWarning` is used as
the category.
"""
warnings.warn(msg, exc.SAWarning, stacklevel=2)
def warn_limited(msg, args):
"""Issue a warning with a parameterized string, limiting the number
of registrations.
"""
if args:
msg = _hash_limit_string(msg, 10, args)
warnings.warn(msg, exc.SAWarning, stacklevel=2)
def only_once(fn, retry_on_exception):
"""Decorate the given function to be a no-op after it is called exactly
once."""
once = [fn]
def go(*arg, **kw):
# strong reference fn so that it isn't garbage collected,
# which interferes with the event system's expectations
strong_fn = fn # noqa
if once:
once_fn = once.pop()
try:
return once_fn(*arg, **kw)
except:
if retry_on_exception:
once.insert(0, once_fn)
raise
return go
_SQLA_RE = re.compile(r"sqlalchemy/([a-z_]+/){0,2}[a-z_]+\.py")
_UNITTEST_RE = re.compile(r"unit(?:2|test2?/)")
def chop_traceback(tb, exclude_prefix=_UNITTEST_RE, exclude_suffix=_SQLA_RE):
"""Chop extraneous lines off beginning and end of a traceback.
:param tb:
a list of traceback lines as returned by ``traceback.format_stack()``
:param exclude_prefix:
a regular expression object matching lines to skip at beginning of
``tb``
:param exclude_suffix:
a regular expression object matching lines to skip at end of ``tb``
"""
start = 0
end = len(tb) - 1
while start <= end and exclude_prefix.search(tb[start]):
start += 1
while start <= end and exclude_suffix.search(tb[end]):
end -= 1
return tb[start : end + 1]
NoneType = type(None)
def attrsetter(attrname):
code = "def set(obj, value):" " obj.%s = value" % attrname
env = locals().copy()
exec(code, env)
return env["set"]
class EnsureKWArgType(type):
r"""Apply translation of functions to accept \**kw arguments if they
don't already.
"""
def __init__(cls, clsname, bases, clsdict):
fn_reg = cls.ensure_kwarg
if fn_reg:
for key in clsdict:
m = re.match(fn_reg, key)
if m:
fn = clsdict[key]
spec = compat.inspect_getfullargspec(fn)
if not spec.varkw:
clsdict[key] = wrapped = cls._wrap_w_kw(fn)
setattr(cls, key, wrapped)
super(EnsureKWArgType, cls).__init__(clsname, bases, clsdict)
def _wrap_w_kw(self, fn):
def wrap(*arg, **kw):
return fn(*arg)
return update_wrapper(wrap, fn)
def wrap_callable(wrapper, fn):
"""Augment functools.update_wrapper() to work with objects with
a ``__call__()`` method.
:param fn:
object with __call__ method
"""
if hasattr(fn, "__name__"):
return update_wrapper(wrapper, fn)
else:
_f = wrapper
_f.__name__ = fn.__class__.__name__
if hasattr(fn, "__module__"):
_f.__module__ = fn.__module__
if hasattr(fn.__call__, "__doc__") and fn.__call__.__doc__:
_f.__doc__ = fn.__call__.__doc__
elif fn.__doc__:
_f.__doc__ = fn.__doc__
return _f
def quoted_token_parser(value):
"""Parse a dotted identifier with accommodation for quoted names.
Includes support for SQL-style double quotes as a literal character.
E.g.::
>>> quoted_token_parser("name")
["name"]
>>> quoted_token_parser("schema.name")
["schema", "name"]
>>> quoted_token_parser('"Schema"."Name"')
['Schema', 'Name']
>>> quoted_token_parser('"Schema"."Name""Foo"')
['Schema', 'Name""Foo']
"""
if '"' not in value:
return value.split(".")
# 0 = outside of quotes
# 1 = inside of quotes
state = 0
result = [[]]
idx = 0
lv = len(value)
while idx < lv:
char = value[idx]
if char == '"':
if state == 1 and idx < lv - 1 and value[idx + 1] == '"':
result[-1].append('"')
idx += 1
else:
state ^= 1
elif char == "." and state == 0:
result.append([])
else:
result[-1].append(char)
idx += 1
return ["".join(token) for token in result]
def add_parameter_text(params, text):
params = _collections.to_list(params)
def decorate(fn):
doc = fn.__doc__ is not None and fn.__doc__ or ""
if doc:
doc = inject_param_text(doc, {param: text for param in params})
fn.__doc__ = doc
return fn
return decorate
def _dedent_docstring(text):
split_text = text.split("\n", 1)
if len(split_text) == 1:
return text
else:
firstline, remaining = split_text
if not firstline.startswith(" "):
return firstline + "\n" + textwrap.dedent(remaining)
else:
return textwrap.dedent(text)
def inject_docstring_text(doctext, injecttext, pos):
doctext = _dedent_docstring(doctext or "")
lines = doctext.split("\n")
if len(lines) == 1:
lines.append("")
injectlines = textwrap.dedent(injecttext).split("\n")
if injectlines[0]:
injectlines.insert(0, "")
blanks = [num for num, line in enumerate(lines) if not line.strip()]
blanks.insert(0, 0)
inject_pos = blanks[min(pos, len(blanks) - 1)]
lines = lines[0:inject_pos] + injectlines + lines[inject_pos:]
return "\n".join(lines)
def inject_param_text(doctext, inject_params):
doclines = doctext.splitlines()
lines = []
to_inject = None
while doclines:
line = doclines.pop(0)
if to_inject is None:
m = re.match(r"(\s+):param (?:\\\*\*?)?(.+?):", line)
if m:
param = m.group(2)
if param in inject_params:
# default indent to that of :param: plus one
indent = " " * len(m.group(1)) + " "
# but if the next line has text, use that line's
# indentntation
if doclines:
m2 = re.match(r"(\s+)\S", doclines[0])
if m2:
indent = " " * len(m2.group(1))
to_inject = indent + inject_params[param]
elif line.lstrip().startswith(":param "):
lines.append("\n")
lines.append(to_inject)
lines.append("\n")
to_inject = None
elif not line.rstrip():
lines.append(line)
lines.append(to_inject)
lines.append("\n")
to_inject = None
elif line.endswith("::"):
# TODO: this still wont cover if the code example itself has blank
# lines in it, need to detect those via indentation.
lines.append(line)
lines.append(
doclines.pop(0)
) # the blank line following a code example
continue
lines.append(line)
return "\n".join(lines)
def repr_tuple_names(names):
"""Trims a list of strings from the middle and return a string of up to
four elements. Strings greater than 11 characters will be truncated"""
if len(names) == 0:
return None
flag = len(names) <= 4
names = names[0:4] if flag else names[0:3] + names[-1:]
res = ["%s.." % name[:11] if len(name) > 11 else name for name in names]
if flag:
return ", ".join(res)
else:
return "%s, ..., %s" % (", ".join(res[0:3]), res[-1])