inspect.signautre: Fix functools.partial support. Issue #21117
This commit is contained in:
Yury Selivanov
parent
7ddf3eba90
commit
0fceaf45e2
133
Lib/inspect.py
133
Lib/inspect.py
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@ -1511,7 +1511,8 @@ def _signature_get_partial(wrapped_sig, partial, extra_args=()):
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# look like after applying a 'functools.partial' object (or alike)
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# on it.
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new_params = OrderedDict(wrapped_sig.parameters.items())
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old_params = wrapped_sig.parameters
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new_params = OrderedDict(old_params.items())
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partial_args = partial.args or ()
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partial_keywords = partial.keywords or {}
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@ -1525,32 +1526,57 @@ def _signature_get_partial(wrapped_sig, partial, extra_args=()):
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msg = 'partial object {!r} has incorrect arguments'.format(partial)
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raise ValueError(msg) from ex
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for arg_name, arg_value in ba.arguments.items():
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param = new_params[arg_name]
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if arg_name in partial_keywords:
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# We set a new default value, because the following code
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# is correct:
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#
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# >>> def foo(a): print(a)
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# >>> print(partial(partial(foo, a=10), a=20)())
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# 20
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# >>> print(partial(partial(foo, a=10), a=20)(a=30))
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# 30
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#
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# So, with 'partial' objects, passing a keyword argument is
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# like setting a new default value for the corresponding
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# parameter
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#
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# We also mark this parameter with '_partial_kwarg'
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# flag. Later, in '_bind', the 'default' value of this
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# parameter will be added to 'kwargs', to simulate
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# the 'functools.partial' real call.
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new_params[arg_name] = param.replace(default=arg_value,
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_partial_kwarg=True)
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elif (param.kind not in (_VAR_KEYWORD, _VAR_POSITIONAL) and
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not param._partial_kwarg):
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new_params.pop(arg_name)
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transform_to_kwonly = False
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for param_name, param in old_params.items():
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try:
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arg_value = ba.arguments[param_name]
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except KeyError:
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pass
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else:
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if param.kind is _POSITIONAL_ONLY:
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# If positional-only parameter is bound by partial,
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# it effectively disappears from the signature
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new_params.pop(param_name)
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continue
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if param.kind is _POSITIONAL_OR_KEYWORD:
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if param_name in partial_keywords:
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# This means that this parameter, and all parameters
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# after it should be keyword-only (and var-positional
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# should be removed). Here's why. Consider the following
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# function:
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# foo(a, b, *args, c):
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# pass
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#
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# "partial(foo, a='spam')" will have the following
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# signature: "(*, a='spam', b, c)". Because attempting
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# to call that partial with "(10, 20)" arguments will
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# raise a TypeError, saying that "a" argument received
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# multiple values.
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transform_to_kwonly = True
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# Set the new default value
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new_params[param_name] = param.replace(default=arg_value)
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else:
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# was passed as a positional argument
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new_params.pop(param.name)
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continue
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if param.kind is _KEYWORD_ONLY:
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# Set the new default value
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new_params[param_name] = param.replace(default=arg_value)
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if transform_to_kwonly:
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assert param.kind is not _POSITIONAL_ONLY
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if param.kind is _POSITIONAL_OR_KEYWORD:
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new_param = new_params[param_name].replace(kind=_KEYWORD_ONLY)
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new_params[param_name] = new_param
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new_params.move_to_end(param_name)
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elif param.kind in (_KEYWORD_ONLY, _VAR_KEYWORD):
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new_params.move_to_end(param_name)
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elif param.kind is _VAR_POSITIONAL:
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new_params.pop(param.name)
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return wrapped_sig.replace(parameters=new_params.values())
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@ -2069,7 +2095,7 @@ class Parameter:
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`Parameter.KEYWORD_ONLY`, `Parameter.VAR_KEYWORD`.
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'''
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__slots__ = ('_name', '_kind', '_default', '_annotation', '_partial_kwarg')
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__slots__ = ('_name', '_kind', '_default', '_annotation')
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POSITIONAL_ONLY = _POSITIONAL_ONLY
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POSITIONAL_OR_KEYWORD = _POSITIONAL_OR_KEYWORD
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@ -2079,8 +2105,7 @@ class Parameter:
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empty = _empty
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def __init__(self, name, kind, *, default=_empty, annotation=_empty,
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_partial_kwarg=False):
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def __init__(self, name, kind, *, default=_empty, annotation=_empty):
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if kind not in (_POSITIONAL_ONLY, _POSITIONAL_OR_KEYWORD,
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_VAR_POSITIONAL, _KEYWORD_ONLY, _VAR_KEYWORD):
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@ -2105,8 +2130,6 @@ class Parameter:
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self._name = name
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self._partial_kwarg = _partial_kwarg
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@property
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def name(self):
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return self._name
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@ -2123,8 +2146,8 @@ class Parameter:
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def kind(self):
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return self._kind
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def replace(self, *, name=_void, kind=_void, annotation=_void,
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default=_void, _partial_kwarg=_void):
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def replace(self, *, name=_void, kind=_void,
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annotation=_void, default=_void):
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'''Creates a customized copy of the Parameter.'''
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if name is _void:
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@ -2139,11 +2162,7 @@ class Parameter:
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if default is _void:
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default = self._default
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if _partial_kwarg is _void:
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_partial_kwarg = self._partial_kwarg
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return type(self)(name, kind, default=default, annotation=annotation,
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_partial_kwarg=_partial_kwarg)
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return type(self)(name, kind, default=default, annotation=annotation)
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def __str__(self):
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kind = self.kind
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@ -2169,17 +2188,6 @@ class Parameter:
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id(self), self.name)
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def __eq__(self, other):
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# NB: We deliberately do not compare '_partial_kwarg' attributes
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# here. Imagine we have a following situation:
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#
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# def foo(a, b=1): pass
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# def bar(a, b): pass
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# bar2 = functools.partial(bar, b=1)
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#
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# For the above scenario, signatures for `foo` and `bar2` should
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# be equal. '_partial_kwarg' attribute is an internal flag, to
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# distinguish between keyword parameters with defaults and
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# keyword parameters which got their defaults from functools.partial
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return (issubclass(other.__class__, Parameter) and
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self._name == other._name and
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self._kind == other._kind and
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@ -2219,12 +2227,7 @@ class BoundArguments:
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def args(self):
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args = []
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for param_name, param in self._signature.parameters.items():
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if (param.kind in (_VAR_KEYWORD, _KEYWORD_ONLY) or
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param._partial_kwarg):
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# Keyword arguments mapped by 'functools.partial'
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# (Parameter._partial_kwarg is True) are mapped
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# in 'BoundArguments.kwargs', along with VAR_KEYWORD &
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# KEYWORD_ONLY
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if param.kind in (_VAR_KEYWORD, _KEYWORD_ONLY):
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break
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try:
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@ -2249,8 +2252,7 @@ class BoundArguments:
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kwargs_started = False
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for param_name, param in self._signature.parameters.items():
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if not kwargs_started:
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if (param.kind in (_VAR_KEYWORD, _KEYWORD_ONLY) or
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param._partial_kwarg):
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if param.kind in (_VAR_KEYWORD, _KEYWORD_ONLY):
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kwargs_started = True
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else:
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if param_name not in self.arguments:
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@ -2332,18 +2334,14 @@ class Signature:
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name = param.name
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if kind < top_kind:
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msg = 'wrong parameter order: {} before {}'
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msg = 'wrong parameter order: {!r} before {!r}'
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msg = msg.format(top_kind, kind)
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raise ValueError(msg)
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elif kind > top_kind:
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kind_defaults = False
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top_kind = kind
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if (kind in (_POSITIONAL_ONLY, _POSITIONAL_OR_KEYWORD) and
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not param._partial_kwarg):
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# If we have a positional-only or positional-or-keyword
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# parameter, that does not have its default value set
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# by 'functools.partial' or other "partial" signature:
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if kind in (_POSITIONAL_ONLY, _POSITIONAL_OR_KEYWORD):
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if param.default is _empty:
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if kind_defaults:
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# No default for this parameter, but the
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@ -2518,15 +2516,6 @@ class Signature:
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parameters_ex = ()
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arg_vals = iter(args)
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if partial:
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# Support for binding arguments to 'functools.partial' objects.
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# See 'functools.partial' case in 'signature()' implementation
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# for details.
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for param_name, param in self.parameters.items():
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if (param._partial_kwarg and param_name not in kwargs):
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# Simulating 'functools.partial' behavior
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kwargs[param_name] = param.default
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while True:
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# Let's iterate through the positional arguments and corresponding
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# parameters
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@ -1959,6 +1959,8 @@ class TestSignatureObject(unittest.TestCase):
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def test_signature_on_partial(self):
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from functools import partial
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Parameter = inspect.Parameter
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def test():
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pass
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@ -1994,15 +1996,22 @@ class TestSignatureObject(unittest.TestCase):
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self.assertEqual(self.signature(partial(test, b=1, c=2)),
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((('a', ..., ..., "positional_or_keyword"),
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('b', 1, ..., "positional_or_keyword"),
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('b', 1, ..., "keyword_only"),
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('c', 2, ..., "keyword_only"),
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('d', ..., ..., "keyword_only")),
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...))
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self.assertEqual(self.signature(partial(test, 0, b=1, c=2)),
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((('b', 1, ..., "positional_or_keyword"),
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((('b', 1, ..., "keyword_only"),
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('c', 2, ..., "keyword_only"),
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('d', ..., ..., "keyword_only"),),
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('d', ..., ..., "keyword_only")),
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...))
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self.assertEqual(self.signature(partial(test, a=1)),
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((('a', 1, ..., "keyword_only"),
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('b', ..., ..., "keyword_only"),
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('c', ..., ..., "keyword_only"),
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('d', ..., ..., "keyword_only")),
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...))
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def test(a, *args, b, **kwargs):
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@ -2014,13 +2023,18 @@ class TestSignatureObject(unittest.TestCase):
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('kwargs', ..., ..., "var_keyword")),
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...))
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self.assertEqual(self.signature(partial(test, a=1)),
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((('a', 1, ..., "keyword_only"),
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('b', ..., ..., "keyword_only"),
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('kwargs', ..., ..., "var_keyword")),
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...))
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self.assertEqual(self.signature(partial(test, 1, 2, 3)),
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((('args', ..., ..., "var_positional"),
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('b', ..., ..., "keyword_only"),
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('kwargs', ..., ..., "var_keyword")),
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...))
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self.assertEqual(self.signature(partial(test, 1, 2, 3, test=True)),
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((('args', ..., ..., "var_positional"),
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('b', ..., ..., "keyword_only"),
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@ -2067,7 +2081,7 @@ class TestSignatureObject(unittest.TestCase):
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return a
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_foo = partial(partial(foo, a=10), a=20)
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self.assertEqual(self.signature(_foo),
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((('a', 20, ..., "positional_or_keyword"),),
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((('a', 20, ..., "keyword_only"),),
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...))
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# check that we don't have any side-effects in signature(),
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# and the partial object is still functioning
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@ -2076,42 +2090,87 @@ class TestSignatureObject(unittest.TestCase):
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def foo(a, b, c):
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return a, b, c
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_foo = partial(partial(foo, 1, b=20), b=30)
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self.assertEqual(self.signature(_foo),
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((('b', 30, ..., "positional_or_keyword"),
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('c', ..., ..., "positional_or_keyword")),
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((('b', 30, ..., "keyword_only"),
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('c', ..., ..., "keyword_only")),
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...))
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self.assertEqual(_foo(c=10), (1, 30, 10))
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_foo = partial(_foo, 2) # now 'b' has two values -
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# positional and keyword
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with self.assertRaisesRegex(ValueError, "has incorrect arguments"):
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inspect.signature(_foo)
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def foo(a, b, c, *, d):
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return a, b, c, d
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_foo = partial(partial(foo, d=20, c=20), b=10, d=30)
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self.assertEqual(self.signature(_foo),
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((('a', ..., ..., "positional_or_keyword"),
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('b', 10, ..., "positional_or_keyword"),
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('c', 20, ..., "positional_or_keyword"),
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('d', 30, ..., "keyword_only")),
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('b', 10, ..., "keyword_only"),
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('c', 20, ..., "keyword_only"),
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('d', 30, ..., "keyword_only"),
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),
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...))
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ba = inspect.signature(_foo).bind(a=200, b=11)
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self.assertEqual(_foo(*ba.args, **ba.kwargs), (200, 11, 20, 30))
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def foo(a=1, b=2, c=3):
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return a, b, c
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_foo = partial(foo, a=10, c=13)
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ba = inspect.signature(_foo).bind(11)
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_foo = partial(foo, c=13) # (a=1, b=2, *, c=13)
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ba = inspect.signature(_foo).bind(a=11)
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self.assertEqual(_foo(*ba.args, **ba.kwargs), (11, 2, 13))
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ba = inspect.signature(_foo).bind(11, 12)
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self.assertEqual(_foo(*ba.args, **ba.kwargs), (11, 12, 13))
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ba = inspect.signature(_foo).bind(11, b=12)
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self.assertEqual(_foo(*ba.args, **ba.kwargs), (11, 12, 13))
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ba = inspect.signature(_foo).bind(b=12)
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self.assertEqual(_foo(*ba.args, **ba.kwargs), (10, 12, 13))
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_foo = partial(_foo, b=10)
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ba = inspect.signature(_foo).bind(12, 14)
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self.assertEqual(_foo(*ba.args, **ba.kwargs), (12, 14, 13))
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self.assertEqual(_foo(*ba.args, **ba.kwargs), (1, 12, 13))
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_foo = partial(_foo, b=10, c=20)
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ba = inspect.signature(_foo).bind(12)
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self.assertEqual(_foo(*ba.args, **ba.kwargs), (12, 10, 20))
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def foo(a, b, c, d, **kwargs):
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pass
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sig = inspect.signature(foo)
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params = sig.parameters.copy()
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params['a'] = params['a'].replace(kind=Parameter.POSITIONAL_ONLY)
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params['b'] = params['b'].replace(kind=Parameter.POSITIONAL_ONLY)
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foo.__signature__ = inspect.Signature(params.values())
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sig = inspect.signature(foo)
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self.assertEqual(str(sig), '(a, b, /, c, d, **kwargs)')
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self.assertEqual(self.signature(partial(foo, 1)),
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((('b', ..., ..., 'positional_only'),
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('c', ..., ..., 'positional_or_keyword'),
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('d', ..., ..., 'positional_or_keyword'),
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('kwargs', ..., ..., 'var_keyword')),
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...))
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self.assertEqual(self.signature(partial(foo, 1, 2)),
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((('c', ..., ..., 'positional_or_keyword'),
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('d', ..., ..., 'positional_or_keyword'),
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('kwargs', ..., ..., 'var_keyword')),
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...))
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self.assertEqual(self.signature(partial(foo, 1, 2, 3)),
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((('d', ..., ..., 'positional_or_keyword'),
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('kwargs', ..., ..., 'var_keyword')),
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...))
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self.assertEqual(self.signature(partial(foo, 1, 2, c=3)),
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((('c', 3, ..., 'keyword_only'),
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('d', ..., ..., 'keyword_only'),
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('kwargs', ..., ..., 'var_keyword')),
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...))
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self.assertEqual(self.signature(partial(foo, 1, c=3)),
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((('b', ..., ..., 'positional_only'),
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('c', 3, ..., 'keyword_only'),
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('d', ..., ..., 'keyword_only'),
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('kwargs', ..., ..., 'var_keyword')),
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...))
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def test_signature_on_partialmethod(self):
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from functools import partialmethod
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@ -106,6 +106,11 @@ Library
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(Original patches by Hirokazu Yamamoto and Amaury Forgeot d'Arc, with
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suggested wording by David Gutteridge)
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- Issue #21117: Fix inspect.signature to better support functools.partial.
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Due to the specifics of functools.partial implementation,
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positional-or-keyword arguments passed as keyword arguments become
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keyword-only.
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IDLE
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----
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